Development Guide

Red Hat JBoss Enterprise Application Platform 7.0

For Use with Red Hat JBoss Enterprise Application Platform 7.0

Red Hat Customer Content Services

Abstract

This book provides references and examples for Java EE developers using Red Hat JBoss Enterprise Application Platform 7.0 and its patch releases.

Chapter 1. Get Started Developing Applications

1.1. Introduction

1.1.1. About Red Hat JBoss Enterprise Application Platform 7

Red Hat JBoss Enterprise Application Platform 7 (JBoss EAP) is a middleware platform built on open standards and compliant with the Java Enterprise Edition 7 specification. It integrates WildFly Application Server 10 with messaging, high-availability clustering, and other technologies.

JBoss EAP includes a modular structure that allows service enabling only when required, improving startup speed.

The management console and management command-line interface (CLI) make editing XML configuration files unnecessary and add the ability to script and automate tasks.

JBoss EAP provides two operating modes for JBoss EAP instances: standalone server or managed domain. The standalone server operating mode represents running JBoss EAP as a single server instance. The managed domain operating mode allows for the management of multiple JBoss EAP instances from a single control point.

In addition, JBoss EAP includes APIs and development frameworks for quickly developing secure and scalable Java EE applications.

1.2. Become Familiar with Java Enterprise Edition 7

1.2.1. Overview of EE 7 Profiles

Java Enterprise Edition 7 (EE 7) includes support for multiple profiles, or subsets of APIs. The only two profiles that the EE 7 specification defines are the Full Profile and the Web Profile.

EE 7 Full Profile includes all APIs and specifications included in the EE 7 specification. EE 7 Web Profile includes a selected subset of APIs, which are designed to be useful to web developers.

JBoss EAP is a certified implementation of the Java Enterprise Edition 7 Full Profile and Web Profile specifications.

Java Enterprise Edition 7 Web Profile

The Web Profile is one of two profiles defined by the Java Enterprise Edition 7 specification, and is designed for web application development. The Web Profile supports the following APIs:

  • Java EE 7 Web Profile Requirements:

    • Java Platform, Enterprise Edition 7
  • Java Web Technologies:

    • Servlet 3.1 (JSR 340)
    • JSP 2.3
    • Expression Language (EL) 3.0
    • JavaServer Faces (JSF) 2.2 (JSR 344)
    • Java Standard Tag Library (JSTL) for JSP 1.2
    • Debugging Support for Other Languages 1.0 (JSR 45)
  • Enterprise Application Technologies:

    • Contexts and Dependency Injection (CDI) 1.1 (JSR 346)
    • Dependency Injection for Java 1.0 (JSR 330)
    • Enterprise JavaBeans 3.2 Lite (JSR 345)
    • Java Persistence API 2.1 (JSR 338)
    • Common Annotations for the Java Platform 1.1 (JSR 250)
    • Java Transaction API (JTA) 1.2 (JSR 907)
    • Bean Validation 1.1 (JSR 349)

The other profile defined by the Java EE 7 specification is the Full Profile, and includes several more APIs.

Java Enterprise Edition 7 Full Profile

The Java Enterprise Edition 7 (EE 7) specification defines a concept of profiles, and defines two of them as part of the specification. The Full Profile supports the following APIs, as well as those supported in the Java Enterprise Edition 7 Web Profile:

  • Included in the EE 7 Full Profile:

    • Batch 1.0
    • JSON-P 1.0
    • Concurrency 1.0
    • WebSocket 1.1
    • JMS 2.0
    • JPA 2.1
    • JCA 1.7
    • JAX-RS 2.0
    • JAX-WS 2.2
    • Servlet 3.1
    • JSF 2.2
    • JSP 2.3
    • EL 3.0
    • CDI 1.1
    • CDI Extensions
    • JTA 1.2
    • Interceptors 1.2
    • Common Annotations 1.1
    • Managed Beans 1.0
    • EJB 3.2
    • Bean Validation 1.1

1.3. Setting Up the Development Environment

1.3.1. Download JBoss Developer Studio

JBoss Developer Studio can be downloaded from the Red Hat Customer Portal.

  1. Log in to the Red Hat Customer Portal.
  2. Click Downloads.
  3. In the Product Downloads list, click Red Hat JBoss Developer Studio.
  4. Select the desired version in the Version drop-down menu.

    Note

    It is recommended to use JBoss Developer Studio version 9.1 or later.

  5. Find the Red Hat JBoss Developer Studio 9.x.x Stand-alone Installer entry in the table and click Download.
  6. Save the JAR file to the desired directory.

1.3.2. Install JBoss Developer Studio

  1. Open a terminal and navigate to the directory containing the downloaded JAR file.
  2. Run the following command to launch the GUI installation program:

    $ java -jar jboss-devstudio-BUILD_VERSION-installer-standalone.jar
    Note

    Alternatively, you may be able to double-click the JAR file to launch the installation program.

  3. Click Next to start the installation process.
  4. Select I accept the terms of this license agreement and click Next.
  5. Adjust the installation path and click Next.

    Note

    If the installation path folder does not exist, a prompt will appear. Click OK to create the folder.

  6. Choose a JVM, or leave the default JVM selected, and click Next.
  7. Click Next when asked to select platforms and servers.
  8. Review the installation details, and click Next.
  9. Click Next when the installation process is complete.
  10. Configure the desktop shortcuts for JBoss Developer Studio, and click Next.
  11. Click Done.

1.3.3. Start JBoss Developer Studio

To start JBoss Developer Studio, you can double-click on the desktop shortcut created during the installation, or you can start it from a command line. Follow the below steps to start JBoss Developer Studio using the command line.

  1. Open a terminal and navigate to the JBoss Developer Studio installation directory.
  2. Run the following command to start JBoss Developer Studio:

    $ ./jbdevstudio
    Note

    For Windows Server, use the jbdevstudio.bat file.

1.3.4. Add the JBoss EAP Server to JBoss Developer Studio

These instructions assume that you have not yet added any JBoss EAP servers to JBoss Developer Studio. Use the following steps to add your JBoss EAP server using the Define New Server wizard.

  1. Open the Servers tab.

    Note

    If the Servers tab is not shown, add it to the panel by selecting WindowShow ViewServers.

  2. Click on the No servers are available. Click this link to create a new server link.

    Figure 1.1. Add a New Server

    The *Servers* tab when no servers are available.
  3. Expand Red Hat JBoss Middleware and choose JBoss Enterprise Application Platform 7.0. Enter a server name, for example, JBoss EAP 7.0, then click Next.

    Figure 1.2. Define a New Server

    The *Define a New Server* window.
  4. Create a server adapter to manage starting and stopping the server. Keep the defaults and click Next.

    Figure 1.3. Create a New Server Adapter

    The *Create a New Server Adapter* window.
  5. Enter a name, for example JBoss EAP 7.0 Runtime. Click Browse next to Home Directory and navigate to your JBoss EAP installation directory. Then click Next.

    Figure 1.4. Add New Server Runtime Environment

    The *JBoss Runtime* window.
    Note

    Some quickstarts require that you run the server with a different profile or additional arguments. For example, to deploy a quickstart that requires the full profile, you must define a new server and specify standalone-full.xml in the Configuration file field. Be sure to give the new server a descriptive name.

  6. Configure existing projects for the new server. Because you do not have any projects at this point, click Finish.

    Figure 1.5. Modify Resources for the New Server

    The *Add and Remove Resources* window.

The JBoss EAP 7.0 server is now listed in the Servers tab.

Figure 1.6. Server List

The *Servers* tab when the `JBoss EAP 7.0` server is listed.

1.4. Using the Quickstart Examples

1.4.1. About Maven

Apache Maven is a distributed build automation tool used in Java application development to create, manage, and build software projects. Maven uses standard configuration files called Project Object Model (POM) files to define projects and manage the build process. POMs describe the module and component dependencies, build order, and targets for the resulting project packaging and output using an XML file. This ensures that the project is built in a correct and uniform manner.

Maven achieves this by using a repository. A Maven repository stores Java libraries, plug-ins, and other build artifacts. The default public repository is the Maven 2 Central Repository, but repositories can be private and internal within a company with a goal to share common artifacts among development teams. Repositories are also available from third-parties. For more information, see the Apache Maven project and the Introduction to Repositories guide.

JBoss EAP includes a Maven repository that contains many of the requirements that Java EE developers typically use to build applications on JBoss EAP.

For more information, see Using Maven with JBoss EAP.

1.4.1.1. Using Maven with the Quickstarts

The artifacts and dependencies needed to build and deploy applications to JBoss EAP 7 are hosted on a public repository. Starting with the JBoss EAP 7 quickstarts, it is no longer necessary to configure your Maven settings.xml file to use these repositories when building the quickstarts. The Maven repositories are now configured in the quickstart project POM files. This method of configuration is provided to make it easier to get started with the quickstarts, however, is generally not recommended for production projects because it can slow down your build.

Red Hat JBoss Developer Studio includes Maven, so there is no need to download and install it separately. It is recommended to use JBoss Developer Studio version 9.1 or later.

If you plan to use the Maven command line to build and deploy your applications, then you must first download Maven from the Apache Maven project and install it using the instructions provided in the Maven documentation.

1.4.2. Download and Run the Quickstart Code Examples

1.4.2.1. Download the Quickstarts

JBoss EAP comes with a comprehensive set of quickstart code examples designed to help users begin writing applications using various Java EE 7 technologies. The quickstarts can be downloaded from the Red Hat Customer Portal.

  1. Log in to the Red Hat Customer Portal.
  2. Click Downloads.
  3. In the Product Downloads list, click Red Hat JBoss Enterprise Application Platform.
  4. Select the desired version in the Version drop-down menu.
  5. Find the Red Hat JBoss Enterprise Application Platform 7.0.0 Quickstarts entry in the table and click Download.
  6. Save the ZIP file to the desired directory.
  7. Extract the ZIP file.

1.4.2.2. Run the Quickstarts in JBoss Developer Studio

Once the quickstarts have been downloaded, they can be imported into JBoss Developer Studio and deployed to JBoss EAP.

Import a Quickstart into JBoss Developer Studio

Each quickstart ships with a POM file that contains its project and configuration information. Use this POM file to easily import the quickstart into JBoss Developer Studio.

Important

If your quickstart project folder is located within the IDE workspace when you import it into JBoss Developer Studio, the IDE generates an invalid project name and WAR archive name. Be sure your quickstart project folder is located outside the IDE workspace before you begin.

  1. Start JBoss Developer Studio.
  2. Select FileImport.
  3. Choose MavenExisting Maven Projects, then click Next.

    Figure 1.7. Import Existing Maven Projects

    The *Import* window.
  4. Browse to the desired quickstart’s directory (for example the helloworld quickstart), and click OK. The Projects list box is populated with the pom.xml file of the selected quickstart project.

    Figure 1.8. Select Maven Projects

    The *Maven Projects* selection window.
  5. Click Finish.

Run the helloworld Quickstart

Running the helloworld quickstart is a simple way to verify that the JBoss EAP server is configured and running correctly.

  1. If you have not yet defined a server, add the JBoss EAP server to JBoss Developer Studio.
  2. Right-click the jboss-helloworld project in the Project Explorer tab and select Run AsRun on Server.

    Figure 1.9. Run As - Run on Server

    The *Run As* -> *Run on Server* screen capture.
  3. Select JBoss EAP 7.0 from the server list and click Next.

    Figure 1.10. Run on Server

    The *Run on Server* window.
  4. The jboss-helloworld quickstart is already listed to be configured on the server. Click Finish to deploy the quickstart.

    Figure 1.11. Modify Resources Configured on the Server

    The *Add and Remove Resources* window.
  5. Verify the results.

    • In the Server tab, the JBoss EAP 7.0 server status changes to Started .
    • The Console tab shows messages detailing the JBoss EAP server start and the helloworld quickstart deployment.

      WFLYUT0021: Registered web context: /jboss-helloworld
      WFLYSRV0010: Deployed "jboss-helloworld.war" (runtime-name : "jboss-helloworld.war")
    • The helloworld application is available at http://localhost:8080/jboss-helloworld and displays the text Hello World!.

Run the bean-validation Quickstart

Some quickstarts, such as the bean-validation quickstart, do not provide a user interface layer and instead provide Arquillian tests to demonstrate functionality.

  1. Import the bean-validation quickstart into JBoss Developer Studio.
  2. In the Servers tab, right-click on the server and choose Start to start the JBoss EAP server. If you do not see a Servers tab or have not yet defined a server, add the JBoss EAP server to Red Hat JBoss Developer Studio.
  3. Right-click on the jboss-bean-validation project in the Project Explorer tab and select Run AsMaven Build.
  4. Enter the following in the Goals input field and then click Run.

    clean test -Parq-wildfly-remote

    Figure 1.12. Edit Configuration

    The *Edit Configuration* window.
  5. Verify the results.

    The Console tab shows the results of the bean-validation Arquillian tests:

    -------------------------------------------------------
     T E S T S
    -------------------------------------------------------
    Running org.jboss.as.quickstarts.bean_validation.test.MemberValidationTest
    Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.189 sec
    
    Results :
    
    Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
    
    [INFO] ------------------------------------------------------------------------
    [INFO] BUILD SUCCESS
    [INFO] ------------------------------------------------------------------------

1.4.2.3. Run the Quickstarts from the Command Line

You can easily build and deploy the quickstarts from the command line using Maven. If you do not yet have Maven installed, see the Apache Maven project to download and install it.

A README.md file is provided at the root directory of the quickstarts that contains general information about system requirements, configuring Maven, adding users, and running the quickstarts.

Each quickstart also contains its own README.md file that provides the specific instructions and Maven commands to run that quickstart.

Run the helloworld Quickstart from the Command Line

  1. Review the README.md file in the root directory of the helloworld quickstart.
  2. Start the JBoss EAP server.

    $ EAP_HOME/bin/standalone.sh
  3. Navigate to the helloworld quickstart directory.
  4. Build and deploy the quickstart using the Maven command provided in the quickstart’s README.md file.

    mvn clean install wildfly:deploy
  5. The helloworld application is now available at http://localhost:8080/jboss-helloworld and displays the text Hello World!.

1.4.3. Review the Quickstart Tutorials

1.4.3.1. Explore the helloworld Quickstart

The helloworld quickstart shows you how to deploy a simple servlet to JBoss EAP. The business logic is encapsulated in a service, which is provided as a Contexts and Dependency Injection (CDI) bean and injected into the Servlet. This quickstart is a starting point to be sure you have configured and started your server properly.

Detailed instructions to build and deploy this quickstart using the command line can be found in the README.html file at the root of the helloworld quickstart directory. This topic shows you how to use Red Hat JBoss Developer Studio to run the quickstart and assumes you have installed Red Hat JBoss Developer Studio, configured Maven, and imported and successfully run the helloworld quickstart.

Prerequisites
Examine the Directory Structure

The code for the helloworld quickstart can be found in the QUICKSTART_HOME/helloworld directory. The helloworld quickstart is comprised of a Servlet and a CDI bean. It also contains a beans.xml file in the application’s WEB-INF directory that has a version number of 1.1 and a bean-discovery-mode of all. This marker file identifies the WAR as a bean archive and tells JBoss EAP to look for beans in this application and to activate the CDI.

The src/main/webapp/ directory contains the files for the quickstart. All the configuration files for this example are located in the WEB-INF/ directory within src/main/webapp/, including the beans.xml file. The src/main/webapp/ directory also includes an index.html file, which uses a simple meta refresh to redirect the user’s browser to the Servlet, which is located at http://localhost:8080/jboss-helloworld/HelloWorld. The quickstart does not require a web.xml file.

Examine the Code

The package declaration and imports have been excluded from these listings. The complete listing is available in the quickstart source code.

  1. Review the HelloWorldServlet code.

    The HelloWorldServlet.java file is located in the src/main/java/org/jboss/as/quickstarts/helloworld/ directory. This servlet sends the information to the browser.

    HelloWorldServlet Class Code Example

    42 @SuppressWarnings("serial")
    43 @WebServlet("/HelloWorld")
    44 public class HelloWorldServlet extends HttpServlet {
    45
    46     static String PAGE_HEADER = "<html><head><title>helloworld</title></head><body>";
    47
    48     static String PAGE_FOOTER = "</body></html>";
    49
    50     @Inject
    51	   HelloService helloService;
    52
    53     @Override
    54     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    55         resp.setContentType("text/html");
    56         PrintWriter writer = resp.getWriter();
    57         writer.println(PAGE_HEADER);
    58         writer.println("<h1>" + helloService.createHelloMessage("World") + "</h1>");
    59         writer.println(PAGE_FOOTER);
    60         writer.close();
    61     }
    62
    63 }

    Table 1.1. HelloWorldServlet Details

    LineNote

    43

    All you need to do is add the @WebServlet annotation and provide a mapping to a URL used to access the servlet.

    46-48

    Every web page needs correctly formed HTML. This quickstart uses static Strings to write the minimum header and footer output.

    50-51

    These lines inject the HelloService CDI bean which generates the actual message. As long as we don’t alter the API of HelloService, this approach allows us to alter the implementation of HelloService at a later date without changing the view layer.

    58

    This line calls into the service to generate the message "Hello World", and write it out to the HTTP request.

  2. Review the HelloService code.

    The HelloService.java file is located in the src/main/java/org/jboss/as/quickstarts/helloworld/ directory. This service simply returns a message. No XML or annotation registration is required.

    HelloService Class Code Example

    public class HelloService {
    
        String createHelloMessage(String name) {
            return "Hello " + name + "!";
        }
    }

1.4.3.2. Explore the numberguess Quickstart

The numberguess quickstart shows you how to create and deploy a simple non-persistant application to JBoss EAP. Information is displayed using a JSF view and business logic is encapsulated in two CDI beans. In the numberguess quickstart, you have ten attempts to guess a number between 1 and 100. After each attempt, you’re told whether your guess was too high or too low.

The code for the numberguess quickstart can be found in the QUICKSTART_HOME/numberguess directory where QUICKSTART_HOME is the directory where you downloaded and unzipped the JBoss EAP quickstarts. The numberguess quickstart is comprised of a number of beans, configuration files, and Facelets (JSF) views, and is packaged as a WAR module.

Detailed instructions to build and deploy this quickstart using the command line can be found in the README.html file at the root of the numberguess quickstart directory. The following examples use Red Hat JBoss Developer Studio to run the quickstart.

Prerequisites
Examine the Configuration Files

All the configuration files for this example are located in the QUICKSTART_HOME/numberguess/src/main/webapp/WEB-INF/ directory of the quickstart.

  1. Examine the faces-config.xml file.

    This quickstart uses the JSF 2.2 version of faces-config.xml filename. A standardized version of Facelets is the default view handler in JSF 2.2 so it requires no configuration. This file consists of only the root element and is simply a marker file to indicate JSF should be enabled in the application.

    <faces-config version="2.2"
       xmlns="http://xmlns.jcp.org/xml/ns/javaee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
          http://xmlns.jcp.org/xml/ns/javaee
          http://xmlns.jcp.org/xml/ns/javaee/web-facesconfig_2_2.xsd">
    
    </faces-config>
  2. Examine the beans.xml file.

    The beans.xml file contains a version number of 1.1 and a bean-discovery-mode of all. This file is a marker file that identifies the WAR as a bean archive and tells JBoss EAP to look for beans in this application and to activate the CDI.

    <beans xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="
          http://xmlns.jcp.org/xml/ns/javaee
          http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd"
        bean-discovery-mode="all">
    </beans>
Note

This quickstart does not need a web.xml file.

1.4.3.2.1. Examine the JSF Code

JSF uses the .xhtml file extension for source files, but delivers the rendered views with the .jsf extension. The home.xhtml file is located in the src/main/webapp/ directory.

JSF Source Code

19<html xmlns="http://www.w3.org/1999/xhtml"
20	xmlns:ui="http://java.sun.com/jsf/facelets"
21	xmlns:h="http://java.sun.com/jsf/html"
22	xmlns:f="http://java.sun.com/jsf/core">
23
24	<head>
25	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
26	<title>Numberguess</title>
27	</head>
28
29	<body>
30	<div id="content">
31		<h1>Guess a number...</h1>
32		<h:form id="numberGuess">
33
34		<!-- Feedback for the user on their guess -->
35	<div style="color: red">
36		<h:messages id="messages" globalOnly="false" />
37		<h:outputText id="Higher" value="Higher!"
38 		  rendered="#{game.number gt game.guess and game.guess ne 0}" />
39		<h:outputText id="Lower" value="Lower!"
40		   rendered="#{game.number lt game.guess and game.guess ne 0}" />
41	</div>
42
43	<!-- Instructions for the user -->
44	<div>
45	I'm thinking of a number between <span
46	id="numberGuess:smallest">#{game.smallest}</span> and <span
47	id="numberGuess:biggest">#{game.biggest}</span>. You have
48	#{game.remainingGuesses} guesses remaining.
49	</div>
50
51	<!-- Input box for the users guess, plus a button to submit, and reset -->
52	<!-- These are bound using EL to our CDI beans -->
53	<div>
54	Your guess:
55	<h:inputText id="inputGuess" value="#{game.guess}"
56		required="true" size="3"
57		disabled="#{game.number eq game.guess}"
58		validator="#{game.validateNumberRange}" />
59		<h:commandButton id="guessButton" value="Guess"
60			action="#{game.check}"
61			disabled="#{game.number eq game.guess}" />
62	</div>
63	<div>
64	<h:commandButton id="restartButton" value="Reset"
65	action="#{game.reset}" immediate="true" />
66	</div>
67	</h:form>
68
69	</div>
70
71	<br style="clear: both" />
72
73	</body>
74</html>

The following line numbers correspond to those seen when viewing the file in JBoss Developer Studio.

Table 1.2. JSF Details

LineNote

36-40

These are the messages which can be sent to the user: "Higher!" and "Lower!"

45-48

As the user guesses, the range of numbers they can guess gets smaller. This sentence changes to make sure they know the number range of a valid guess.

55-58

This input field is bound to a bean property using a value expression.

58

A validator binding is used to make sure the user does not accidentally input a number outside of the range in which they can guess. If the validator was not here, the user might use up a guess on an out of bounds number.

59-61

There must be a way for the user to send their guess to the server. Here we bind to an action method on the bean.

1.4.3.2.2. Examine the Class Files

All of the numberguess quickstart source files can be found in the QUICKSTART_HOME/numberguess/src/main/java/org/jboss/as/quickstarts/numberguess/ directory. The package declaration and imports have been excluded from these listings. The complete listing is available in the quickstart source code.

  1. Review the Random.java Qualifier Code

    A qualifier is used to remove ambiguity between two beans, both of which are eligible for injection based on their type. For more information on qualifiers, see Use a Qualifier to Resolve an Ambiguous Injection. The @Random qualifier is used for injecting a random number.

    @Target({ TYPE, METHOD, PARAMETER, FIELD })
    @Retention(RUNTIME)
    @Documented
    @Qualifier
    public @interface Random {
    
    }
  2. Review the MaxNumber.java Qualifier Code

    The @MaxNumber qualifier is used for injecting the maximum number allowed.

    @Target({ TYPE, METHOD, PARAMETER, FIELD })
    @Retention(RUNTIME)
    @Documented
    @Qualifier
    public @interface MaxNumber {
    }
  3. Review the Generator.java Code

    The Generator class creates the random number via a producer method, exposing the maximum possible number via the same. This class is application-scoped, so you don’t get a different random each time.

    @SuppressWarnings("serial")
    @ApplicationScoped
    public class Generator implements Serializable {
    
        private java.util.Random random = new java.util.Random(System.currentTimeMillis());
    
        private int maxNumber = 100;
    
        java.util.Random getRandom() {
            return random;
        }
    
        @Produces
        @Random
        int next() {
            // a number between 1 and 100
            return getRandom().nextInt(maxNumber - 1) + 1;
        }
    
        @Produces
        @MaxNumber
        int getMaxNumber() {
            return maxNumber;
        }
    }
  4. Review the Game.java Code

    The session-scoped Game class is the primary entry point of the application. It is responsible for setting up or resetting the game, capturing and validating the user’s guess, and providing feedback to the user with a FacesMessage. It uses the post-construct lifecycle method to initialize the game by retrieving a random number from the @Random Instance`<Integer>` bean.

    Notice the @Named annotation in the class. This annotation is only required when you want to make the bean accessible to a JSF view by using Expression Language (EL), in this case #{game}.

    @SuppressWarnings("serial")
    @Named
    @SessionScoped
    public class Game implements Serializable {
    
        /**
         * The number that the user needs to guess
         */
        private int number;
    
        /**
         * The users latest guess
         */
        private int guess;
    
        /**
         * The smallest number guessed so far (so we can track the valid guess range).
         */
        private int smallest;
    
        /**
         * The largest number guessed so far
         */
        private int biggest;
    
        /**
         * The number of guesses remaining
         */
        private int remainingGuesses;
    
        /**
         * The maximum number we should ask them to guess
         */
        @Inject
        @MaxNumber
        private int maxNumber;
    
        /**
         * The random number to guess
         */
        @Inject
        @Random
        Instance<Integer> randomNumber;
    
        public Game() {
        }
    
        public int getNumber() {
            return number;
        }
    
        public int getGuess() {
            return guess;
        }
    
        public void setGuess(int guess) {
            this.guess = guess;
        }
    
        public int getSmallest() {
            return smallest;
        }
    
        public int getBiggest() {
            return biggest;
        }
    
        public int getRemainingGuesses() {
            return remainingGuesses;
        }
    
        /**
         * Check whether the current guess is correct, and update the biggest/smallest guesses as needed. Give feedback to the user
         * if they are correct.
         */
        public void check() {
            if (guess > number) {
                biggest = guess - 1;
            } else if (guess < number) {
                smallest = guess + 1;
            } else if (guess == number) {
                FacesContext.getCurrentInstance().addMessage(null, new FacesMessage("Correct!"));
            }
            remainingGuesses--;
        }
    
        /**
         * Reset the game, by putting all values back to their defaults, and getting a new random number. We also call this method
         * when the user starts playing for the first time using {@linkplain PostConstruct @PostConstruct} to set the initial
         * values.
         */
        @PostConstruct
        public void reset() {
            this.smallest = 0;
            this.guess = 0;
            this.remainingGuesses = 10;
            this.biggest = maxNumber;
            this.number = randomNumber.get();
        }
    
        /**
         * A JSF validation method which checks whether the guess is valid. It might not be valid because there are no guesses left,
         * or because the guess is not in range.
         *
         */
        public void validateNumberRange(FacesContext context, UIComponent toValidate, Object value) {
            if (remainingGuesses <= 0) {
                FacesMessage message = new FacesMessage("No guesses left!");
                context.addMessage(toValidate.getClientId(context), message);
                ((UIInput) toValidate).setValid(false);
                return;
            }
            int input = (Integer) value;
    
            if (input < smallest || input > biggest) {
                ((UIInput) toValidate).setValid(false);
    
                FacesMessage message = new FacesMessage("Invalid guess");
                context.addMessage(toValidate.getClientId(context), message);
            }
        }
    }

1.5. Configure the Default Welcome Web Application

JBoss EAP includes a default Welcome application, which displays at the root context on port 8080 by default.

This default Welcome application can be replaced with your own web application. This can be configured in one of two ways:

You can also disable the welcome content.

Changing the welcome-content File Handler

Modify the existing welcome-content file handler’s path to point to the new deployment.

/subsystem=undertow/configuration=handler/file=welcome-content:write-attribute(name=path,value="/path/to/content")
Note

Alternatively, you could create a different file handler to be used by the server’s root.

/subsystem=undertow/configuration=handler/file=NEW_FILE_HANDLER:add(path="/path/to/content")
/subsystem=undertow/server=default-server/host=default-host/location=\/:write-attribute(name=handler,value=NEW_FILE_HANDLER)

Reload the server for the changes to take effect.

reload

Changing the default-web-module

Map a deployed web application to the server’s root.

/subsystem=undertow/server=default-server/host=default-host:write-attribute(name=default-web-module,value=hello.war)

Reload the server for the changes to take effect.

reload

Disabling the Default Welcome Web Application

Disable the welcome application by removing the location entry (/) for the default-host.

/subsystem=undertow/server=default-server/host=default-host/location=\/:remove

Reload the server for the changes to take effect.

reload

Chapter 2. Using Maven with JBoss EAP

2.1. Learn about Maven

2.1.1. About the Maven Repository

Apache Maven is a distributed build automation tool used in Java application development to create, manage, and build software projects. Maven uses standard configuration files called Project Object Model, or POM, files to define projects and manage the build process. POMs describe the module and component dependencies, build order, and targets for the resulting project packaging and output using an XML file. This ensures that the project is built in a correct and uniform manner.

Maven achieves this by using a repository. A Maven repository stores Java libraries, plug-ins, and other build artifacts. The default public repository is the Maven 2 Central Repository, but repositories can be private and internal within a company with a goal to share common artifacts among development teams. Repositories are also available from third-parties. JBoss EAP includes a Maven repository that contains many of the requirements that Java EE developers typically use to build applications on JBoss EAP. To configure your project to use this repository, see Configure the JBoss EAP Maven Repository.

For more information about Maven, see Welcome to Apache Maven.

For more information about Maven repositories, see Apache Maven Project - Introduction to Repositories.

2.1.2. About the Maven POM File

The Project Object Model, or POM, file is a configuration file used by Maven to build projects. It is an XML file that contains information about the project and how to build it, including the location of the source, test, and target directories, the project dependencies, plug-in repositories, and goals it can execute. It can also include additional details about the project including the version, description, developers, mailing list, license, and more. A pom.xml file requires some configuration options and will default all others.

The schema for the pom.xml file can be found at http://maven.apache.org/maven-v4_0_0.xsd.

For more information about POM files, see the Apache Maven Project POM Reference.

Minimum Requirements of a Maven POM File

The minimum requirements of a pom.xml file are as follows:

  • project root
  • modelVersion
  • groupId - the id of the project’s group
  • artifactId - the id of the artifact (project)
  • version - the version of the artifact under the specified group

Example: Sample pom.xml file

A basic pom.xml file might look like this:

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.jboss.app</groupId>
  <artifactId>my-app</artifactId>
  <version>1</version>
</project>

2.1.3. About the Maven Settings File

The Maven settings.xml file contains user-specific configuration information for Maven. It contains information that must not be distributed with the pom.xml file, such as developer identity, proxy information, local repository location, and other settings specific to a user.

There are two locations where the settings.xml can be found:

  • In the Maven installation: The settings file can be found in the $M2_HOME/conf/ directory. These settings are referred to as global settings. The default Maven settings file is a template that can be copied and used as a starting point for the user settings file.
  • In the user’s installation: The settings file can be found in the ${user.home}/.m2/ directory. If both the Maven and user settings.xml files exist, the contents are merged. Where there are overlaps, the user’s settings.xml file takes precedence.

Example: Maven Settings file

<?xml version="1.0" encoding="UTF-8"?>
<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
  <profiles>
    <!-- Configure the JBoss EAP Maven repository -->
    <profile>
      <id>jboss-eap-maven-repository</id>
      <repositories>
        <repository>
          <id>jboss-eap</id>
          <url>file:///path/to/repo/jboss-eap-7.0.0.GA-maven-repository/maven-repository</url>
          <releases>
            <enabled>true</enabled>
          </releases>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
        </repository>
      </repositories>
      <pluginRepositories>
        <pluginRepository>
          <id>jboss-eap-maven-plugin-repository</id>
          <url>file:///path/to/repo/jboss-eap-7.0.0.GA-maven-repository/maven-repository</url>
          <releases>
            <enabled>true</enabled>
          </releases>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
        </pluginRepository>
      </pluginRepositories>
    </profile>
  </profiles>
  <activeProfiles>
    <!-- Optionally, make the repository active by default -->
    <activeProfile>jboss-eap-maven-repository</activeProfile>
  </activeProfiles>
</settings>

The schema for the settings.xml file can be found at http://maven.apache.org/xsd/settings-1.0.0.xsd.

2.1.4. About Maven Repository Managers

A repository manager is a tool that allows you to easily manage Maven repositories. Repository managers are useful in multiple ways:

  • They provide the ability to configure proxies between your organization and remote Maven repositories. This provides a number of benefits, including faster and more efficient deployments and a better level of control over what is downloaded by Maven.
  • They provide deployment destinations for your own generated artifacts, allowing collaboration between different development teams across an organization.

For more information about Maven repository managers, see Best Practice - Using a Repository Manager.

Commonly used Maven repository managers
Sonatype Nexus
See Sonatype Nexus documentation for more information about Nexus.
Artifactory
See JFrog Artifactory documentation for more information about Artifactory.
Apache Archiva
See Apache Archiva: The Build Artifact Repository Manager for more information about Apache Archiva.
Note

In an Enterprise environment, where a repository manager is usually used, Maven should query all artifacts for all projects using this manager. Because Maven uses all declared repositories to find missing artifacts, if it can not find what it is looking for, it will try and look for it in the repository central (defined in the built-in parent POM). To override this central location, you can add a definition with central so that the default repository central is now your repository manager as well. This works well for established projects, but for clean or 'new' projects it causes a problem as it creates a cyclic dependency.

2.2. Install Maven and the JBoss EAP Maven Repository

2.2.1. Download and Install Maven

If you plan to use Maven command line to build and deploy your applications to JBoss EAP, you must download and install Maven. If you plan to use Red Hat JBoss Developer Studio to build and deploy your applications, you can skip this procedure as Maven is distributed with Red Hat JBoss Developer Studio.

  1. Go to Apache Maven Project - Download Maven and download the latest distribution for your operating system.
  2. See the Maven documentation for information on how to download and install Apache Maven for your operating system.

2.2.2. Install the JBoss EAP Maven Repository

There are three ways to install the JBoss EAP Maven repository.

Note

You can use the JBoss EAP Maven repository available online, or download and install it locally using any one of the three listed methods.

2.2.3. Install the JBoss EAP Maven Repository Locally

This example covers the steps to download the JBoss EAP Maven Repository to the local file system. This option is easy to configure and allows you to get up and running quickly on your local machine. It can help you become familiar with using Maven for development but is not recommended for team production environments.

Follow these steps to download and install the JBoss EAP Maven repository to the local file system.

  1. Open a web browser and access this URL: https://access.redhat.com/jbossnetwork/restricted/listSoftware.html?product=appplatform.
  2. Find Red Hat JBoss Enterprise Application Platform 7.0 Maven Repository in the list.
  3. Click the Download button to download a .zip file containing the repository.
  4. Unzip the file on the local file system into a directory of your choosing.

    This creates a new jboss-eap-7.0.0.GA-maven-repository/ directory, which contains the Maven repository in a subdirectory named maven-repository/.

Important

If you want to continue to use an older local repository, you must configure it separately in the Maven settings.xml configuration file. Each local repository must be configured within its own <repository> tag.

Important

When downloading a new Maven repository, remove the cached repository/ subdirectory located under the .m2/ directory before attempting to use it.

2.2.4. Install the JBoss EAP Maven Repository for Use with Apache httpd

This example will cover the steps to download the JBoss EAP Maven Repository for use with Apache httpd. This option is good for multi-user and cross-team development environments because any developer that can access the web server can also access the Maven repository.

Note

You must first configure Apache httpd. See Apache HTTP Server Project documentation for instructions.

  1. Open a web browser and access this URL: https://access.redhat.com/jbossnetwork/restricted/listSoftware.html?product=appplatform.
  2. Find Red Hat JBoss Enterprise Application Platform 7.0 Maven Repository in the list.
  3. Click the Download button to download a .zip file containing the repository.
  4. Unzip the files in a directory that is web accessible on the Apache server.
  5. Configure Apache to allow read access and directory browsing in the created directory.

    This configuration allows a multi-user environment to access the Maven repository on Apache httpd.

2.3. Use the Maven Repository

2.3.1. Configure the JBoss EAP Maven Repository

Overview

There are two approaches to direct Maven to use the JBoss EAP Maven Repository in your project:

Configure the JBoss EAP Maven Repository Using the Maven Settings

This is the recommended approach. Maven settings used with a repository manager or repository on a shared server provide better control and manageability of projects. Settings also provide the ability to use an alternative mirror to redirect all lookup requests for a specific repository to your repository manager without changing the project files. For more information about mirrors, see http://maven.apache.org/guides/mini/guide-mirror-settings.html.

This method of configuration applies across all Maven projects, as long as the project POM file does not contain repository configuration.

This section describes how to configure the Maven settings. You can configure the Maven install global settings or the user’s install settings.

Configure the Maven Settings File

  1. Locate the Maven settings.xml file for your operating system. It is usually located in the ${user.home}/.m2/ directory.

    • For Linux or Mac, this is ~/.m2/
    • For Windows, this is \Documents and Settings\.m2\ or \Users\.m2\
  2. If you do not find a settings.xml file, copy the settings.xml file from the ${user.home}/.m2/conf/ directory into the ${user.home}/.m2/ directory.
  3. Copy the following XML into the <profiles> element of the settings.xml file. Determine the URL of the JBoss EAP repository and replace JBOSS_EAP_REPOSITORY_URL with it.

    <!-- Configure the JBoss Enterprise Maven repository -->
    <profile>
      <id>jboss-enterprise-maven-repository</id>
      <repositories>
        <repository>
          <id>jboss-enterprise-maven-repository</id>
          <url>JBOSS_EAP_REPOSITORY_URL</url>
          <releases>
            <enabled>true</enabled>
          </releases>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
        </repository>
      </repositories>
      <pluginRepositories>
        <pluginRepository>
          <id>jboss-enterprise-maven-repository</id>
          <url>JBOSS_EAP_REPOSITORY_URL</url>
          <releases>
            <enabled>true</enabled>
          </releases>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
        </pluginRepository>
      </pluginRepositories>
    </profile>

    The following is an example configuration that accesses the online JBoss EAP Maven repository.

    <!-- Configure the JBoss Enterprise Maven repository -->
    <profile>
      <id>jboss-enterprise-maven-repository</id>
      <repositories>
        <repository>
          <id>jboss-enterprise-maven-repository</id>
          <url>https://maven.repository.redhat.com/ga/</url>
          <releases>
            <enabled>true</enabled>
          </releases>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
        </repository>
      </repositories>
      <pluginRepositories>
        <pluginRepository>
          <id>jboss-enterprise-maven-repository</id>
          <url>https://maven.repository.redhat.com/ga/</url>
          <releases>
            <enabled>true</enabled>
          </releases>
          <snapshots>
            <enabled>false</enabled>
          </snapshots>
        </pluginRepository>
      </pluginRepositories>
    </profile>
  4. Copy the following XML into the <activeProfiles> element of the settings.xml file.

    <activeProfile>jboss-enterprise-maven-repository</activeProfile>
  5. If you modify the settings.xml file while Red Hat JBoss Developer Studio is running, you must refresh the user settings.

    1. From the menu, choose Window → Preferences.
    2. In the Preferences window, expand Maven and choose User Settings.
    3. Click the Update Settings button to refresh the Maven user settings in Red Hat JBoss Developer Studio.

      The Update Maven User Settings screen shot

      The Update Maven User Settings screen shot

Important

If your Maven repository contains outdated artifacts, you may encounter one of the following Maven error messages when you build or deploy your project:

  • Missing artifact ARTIFACT_NAME
  • [ERROR] Failed to execute goal on project PROJECT_NAME; Could not resolve dependencies for PROJECT_NAME

To resolve the issue, delete the cached version of your local repository to force a download of the latest Maven artifacts. The cached repository is located here: ${user.home}/.m2/repository/

Configure the JBoss EAP Maven Repository Using the Project POM
Warning

You should avoid this method of configuration as it overrides the global and user Maven settings for the configured project.

You must plan carefully if you decide to configure repositories using project POM file. Transitively included POMs are an issue with this type of configuration since Maven has to query the external repositories for missing artifacts and this slows the build process. It can also cause you to lose control over where your artifacts are coming from.

Note

The URL of the repository will depend on where the repository is located: on the file system, or web server. For information on how to install the repository, see: Install the JBoss EAP Maven Repository. The following are examples for each of the installation options:

File System
file:///path/to/repo/jboss-eap-maven-repository
Apache Web Server
http://intranet.acme.com/jboss-eap-maven-repository/
Nexus Repository Manager
https://intranet.acme.com/nexus/content/repositories/jboss-eap-maven-repository

Configuring the Project’s POM File

  1. Open your project’s pom.xml file in a text editor.
  2. Add the following repository configuration. If there is already a <repositories> configuration in the file, then add the <repository> element to it. Be sure to change the <url> to the actual repository location.
<repositories>
   <repository>
      <id>jboss-eap-repository-group</id>
      <name>JBoss EAP Maven Repository</name>
      <url>JBOSS_EAP_REPOSITORY_URL</url>
      <layout>default</layout>
      <releases>
         <enabled>true</enabled>
         <updatePolicy>never</updatePolicy>
      </releases>
      <snapshots>
         <enabled>true</enabled>
         <updatePolicy>never</updatePolicy>
      </snapshots>
   </repository>
</repositories>
  1. Add the following plug-in repository configuration. If there is already a <pluginRepositories> configuration in the file, then add the <pluginRepository> element to it.
<pluginRepositories>
   <pluginRepository>
      <id>jboss-eap-repository-group</id>
      <name>JBoss EAP Maven Repository</name>
      <url>JBOSS_EAP_REPOSITORY_URL</url>
      <releases>
         <enabled>true</enabled>
      </releases>
      <snapshots>
         <enabled>true</enabled>
      </snapshots>
   </pluginRepository>
</pluginRepositories>
Determine the URL of the JBoss EAP Repository

The repository URL depends on where the repository is located. You can configure Maven to use any of the following repository locations.

  • To use the online JBoss EAP Maven repository, specify the following URL: https://maven.repository.redhat.com/ga/
  • To use a JBoss EAP Maven repository installed on the local file system, you must download the repository and then use the local file path for the URL. For example: file:///path/to/repo/jboss-eap-7.0-maven-repository/maven-repository/
  • If you install the repository on an Apache Web Server, the repository URL will be similar to the following: http://intranet.acme.com/jboss-eap-7.0-maven-repository/maven-repository/
  • If you install the JBoss EAP Maven repository using the Nexus Repository Manager, the URL will look something like the following: https://intranet.acme.com/nexus/content/repositories/jboss-eap-7.0-maven-repository/maven-repository/
Note

Remote repositories are accessed using common protocols such as http:// for a repository on an HTTP server or file:// for a repository on a file server.

2.3.2. Configure Maven for Use with Red Hat JBoss Developer Studio

The artifacts and dependencies needed to build and deploy applications to Red Hat JBoss Enterprise Application Platform are hosted on a public repository. You must direct Maven to use this repository when you build your applications. This topic covers the steps to configure Maven if you plan to build and deploy applications using Red Hat JBoss Developer Studio.

Maven is distributed with Red Hat JBoss Developer Studio, so it is not necessary to install it separately. However, you must configure Maven for use by the Java EE Web Project wizard for deployments to JBoss EAP. The procedure below demonstrates how to configure Maven for use with JBoss EAP by editing the Maven configuration file from within Red Hat JBoss Developer Studio.

Configure Maven in Red Hat JBoss Developer Studio

  1. Click Window → Preferences, expand JBoss Tools and select JBoss Maven Integration.

    JBoss Maven Integration Pane in the Preferences Window

    JBoss Maven Integration Pane in the Preferences Window

  2. Click Configure Maven Repositories.
  3. Click Add Repository to configure the JBoss Enterprise Maven repository. Complete the Add Maven Repository dialog as follows:

    1. Set the Profile ID, Repository ID, and Repository Name values to jboss-ga-repository.
    2. Set the Repository URL value to http://maven.repository.redhat.com/ga.
    3. Click the Active by default checkbox to enable the Maven repository.
    4. Click OK.

      Add Maven Repository

      Add Maven Repository

  4. Review the repositories and click Finish.

    Review Maven Repositories

    Review Maven Repositories

  5. You are prompted with the message "Are you sure you want to update the file MAVEN_HOME/settings.xml?". Click Yes to update the settings. Click OK to close the dialog.

The JBoss EAP Maven repository is now configured for use with Red Hat JBoss Developer Studio.

2.3.3. Manage Project Dependencies

This topic describes the usage of Bill of Materials (BOM) POMs for Red Hat JBoss Enterprise Application Platform.

A BOM is a Maven pom.xml (POM) file that specifies the versions of all runtime dependencies for a given module. Version dependencies are listed in the dependency management section of the file.

A project uses a BOM by adding its groupId:artifactId:version (GAV) to the dependency management section of the project pom.xml file and specifying the <scope>import</scope> and <type>pom</type> element values.

Note

In many cases, dependencies in project POM files use the provided scope. This is because these classes are provided by the application server at runtime and it is not necessary to package them with the user application.

Supported Maven Artifacts

As part of the product build process, all runtime components of JBoss EAP are built from source in a controlled environment. This helps to ensure that the binary artifacts do not contain any malicious code, and that they can be supported for the life of the product. These artifacts can be easily identified by the -redhat version qualifier, for example 1.0.0-redhat-1.

Adding a supported artifact to the build configuration pom.xml file ensures that the build is using the correct binary artifact for local building and testing. Note that an artifact with a -redhat version is not necessarily part of the supported public API, and may change in future revisions. For information about the public supported API, see the JavaDoc documentation included in the release.

For example, to use the supported version of Hibernate, add something similar to the following to your build configuration.

<dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate-core</artifactId>
  <version>5.0.1.Final-redhat-1</version>
  <scope>provided</scope>
</dependency>

Notice that the above example includes a value for the <version/> field. However, it is recommended to use Maven dependency management for configuring dependency versions.

Dependency Management

Maven includes a mechanism for managing the versions of direct and transitive dependencies throughout the build. For general information about using dependency management, see the Apache Maven Project: Introduction to the Dependency Mechanism.

Using one or more supported Red Hat dependencies directly in your build does not guarantee that all transitive dependencies of the build will be fully supported Red Hat artifacts. It is common for Maven builds to use a mix of artifact sources from the Maven central repository and other Maven repositories.

There is a dependency management BOM included in the JBoss EAP Maven repository, which specifies all the supported JBoss EAP binary artifacts. This BOM can be used in a build to ensure that Maven will prioritize supported JBoss EAP dependencies for all direct and transitive dependencies in the build. In other words, transitive dependencies will be managed to the correct supported dependency version where applicable. The version of this BOM matches the version of the JBoss EAP release.

<dependencyManagement>
  <dependencies>
    ...
    <dependency>
      <groupId>org.jboss.bom</groupId>
      <artifactId>eap-runtime-artifacts</artifactId>
      <version>7.0.0.GA</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    ...
  </dependencies>
</dependencyManagement>
Note

In JBoss EAP 7 the name of this BOM was changed from eap6-supported-artifacts to eap-runtime-artifacts. The purpose of this change is to make it more clear that the artifacts in this POM are part of the JBoss EAP runtime, but are not necessarily part of the supported public API. Some of the jars contain internal API and functionality which may change between releases.

JBoss EAP Java EE Specs BOM

The jboss-javaee-7.0 BOM contains the Java EE Specification API JARs used by JBoss EAP.

To use this BOM in a project, add a dependency for the GAV that contains the version of the JSP and Servlet API JARs needed to build and deploy the application.

The following example uses the 1.0.3.Final-redhat-1 version of the jboss-javaee-7.0 BOM.

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.jboss.spec</groupId>
      <artifactId>jboss-javaee-7.0</artifactId>
      <version>1.0.3.Final-redhat-1</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    ...
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>org.jboss.spec.javax.servlet</groupId>
    <artifactId>jboss-servlet-api_3.1_spec</artifactId>
    <scope>provided</scope>
  </dependency>
  <dependency>
    <groupId>org.jboss.spec.javax.servlet.jsp</groupId>
    <artifactId>jboss-jsp-api_2.3_spec</artifactId>
    <scope>provided</scope>
  </dependency>
  ...
</dependencies>
JBoss EAP BOMs and Quickstarts

The quickstarts provide the primary use case examples for the Maven repository. The following table lists the Maven BOMs used by the quickstarts.

Table 2.1. JBoss BOMs Used by the Quickstarts

BOM Artifact IDUse Case

jboss-eap-javaee7

Supported JBoss EAP JavaEE 7 APIs plus additional JBoss EAP API jars

jboss-eap-javaee7-with-spring3

jboss-eap-javaee7 plus recommended Spring 3 versions

jboss-eap-javaee7-with-spring4

jboss-eap-javaee7 plus recommended Spring 4 versions

jjboss-eap-javaee7-with-tools

jboss-eap-javaee7 plus development tools such as Arquillian

Note

These BOMs from JBoss EAP 6 have been consolidated into fewer BOMs to make usage simpler for most use cases. The Hibernate, logging, transactions, messaging, and other public API jars are now included in jboss-javaee7-eap instead of a requiring a separate BOM for each case.

The following example uses the 7.0.0.GA version of the jboss-eap-javaee7 BOM.

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>org.jboss.bom</groupId>
      <artifactId>jboss-eap-javaee7</artifactId>
      <version>7.0.0.GA</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
    ...
  </dependencies>
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <scope>provided</scope>
  </dependency>
  ...
</dependencies>
JBoss EAP Client BOMs

The client BOMs do not create a dependency management section or define dependencies. Instead, they are an aggregate of other BOMs and are used to package the set of dependencies necessary for a remote client use case.

The wildfly-ejb-client-bom and wildfly-jms-client-bom BOMs are managed by the jboss-eap-javaee7 BOM, so there is no need to manage the versions in your project dependencies.

The following is an example of how to add the wildfly-ejb-client-bom and wildfly-jms-client-bom client BOM dependencies to your project.

<dependencyManagement>
  <dependencies>
    <!-- jboss-eap-javaee7: JBoss stack of the Java EE APIs and related components.  -->
    <dependency>
      <groupId>org.jboss.bom</groupId>
      <artifactId>jboss-eap-javaee7</artifactId>
      <version>7.0.0.GA</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
  ...
</dependencyManagement>

<dependencies>
  <dependency>
    <groupId>org.jboss.eap</groupId>
    <artifactId>wildfly-ejb-client-bom</artifactId>
    <type>pom</type>
  </dependency>
  <dependency>
    <groupId>org.jboss.eap</groupId>
    <artifactId>wildfly-jms-client-bom</artifactId>
    <type>pom</type>
  </dependency>
  ...
</dependencies>

For more information about Maven Dependencies and BOM POM files, see Apache Maven Project - Introduction to the Dependency Mechanism.

Chapter 3. Class Loading and Modules

3.1. Introduction

3.1.1. Overview of Class Loading and Modules

JBoss EAP uses a modular class loading system for controlling the class paths of deployed applications. This system provides more flexibility and control than the traditional system of hierarchical class loaders. Developers have fine-grained control of the classes available to their applications, and can configure a deployment to ignore classes provided by the application server in favor of their own.

The modular class loader separates all Java classes into logical groups called modules. Each module can define dependencies on other modules in order to have the classes from that module added to its own class path. Because each deployed JAR and WAR file is treated as a module, developers can control the contents of their application’s class path by adding module configuration to their application.

3.1.2. Modules

A module is a logical grouping of classes used for class loading and dependency management. JBoss EAP identifies two different types of modules: static and dynamic. The main difference between the two is how they are packaged.

Static Modules

Static modules are defined in the EAP_HOME/modules/ directory of the application server. Each module exists as a subdirectory, for example EAP_HOME/modules/com/mysql/. Each module directory then contains a slot subdirectory, which defaults to main and contains the module.xml configuration file and any required JAR files. All the application server-provided APIs are provided as static modules, including the Java EE APIs as well as other APIs.

Example MySQL JDBC Driver module.xml File

<?xml version="1.0" ?>
<module xmlns="urn:jboss:module:1.1" name="com.mysql">
  <resources>
    <resource-root path="mysql-connector-java-5.1.36-bin.jar"/>
  </resources>
  <dependencies>
    <module name="javax.api"/>
    <module name="javax.transaction.api"/>
  </dependencies>
</module>

The module name (com.mysql) must match the directory structure for the module, excluding the slot name (main).

Creating custom static modules can be useful if many applications are deployed on the same server that use the same third-party libraries. Instead of bundling those libraries with each application, a module containing these libraries can be created and installed by an administrator. The applications can then declare an explicit dependency on the custom static modules.

The modules provided in JBoss EAP distributions are located in the system directory within the EAP_HOME/modules directory. This keeps them separate from any modules provided by third parties. Any Red Hat provided products that layer on top of JBoss EAP also install their modules within the system directory.

Users must ensure that custom modules are installed into the EAP_HOME/modules directory, using one directory per module. This ensures that custom versions of modules that already exist in the system directory are loaded instead of the shipped versions. In this way, user-provided modules will take precedence over system modules.

If you use the JBOSS_MODULEPATH environment variable to change the locations in which JBoss EAP searches for modules, then the product will look for a system subdirectory structure within one of the locations specified. A system structure must exist somewhere in the locations specified with JBOSS_MODULEPATH.

Dynamic Modules

Dynamic modules are created and loaded by the application server for each JAR or WAR deployment (or subdeployment in an EAR). The name of a dynamic module is derived from the name of the deployed archive. Because deployments are loaded as modules, they can configure dependencies and be used as dependencies by other deployments.

Modules are only loaded when required. This usually only occurs when an application is deployed that has explicit or implicit dependencies.

3.1.3. Module Dependencies

A module dependency is a declaration that one module requires the classes of one or more other modules in order to function. When JBoss EAP loads a module, the modular class loader parses the dependencies of that module and adds the classes from each dependency to its class path. If a specified dependency cannot be found, the module will fail to load.

Note

See the Modules section for complete details about modules and the modular class loading system.

Deployed applications (a JAR or WAR, for example) are loaded as dynamic modules and make use of dependencies to access the APIs provided by JBoss EAP.

There are two types of dependencies: explicit and implicit.

Explicit Dependencies
Explicit dependencies are declared by the developer in a configuration file. A static module can declare dependencies in its module.xml file. A dynamic module can declare dependencies in the deployment’s MANIFEST.MF or jboss-deployment-structure.xml deployment descriptor.
Implicit Dependencies

Implicit dependencies are added automatically by JBoss EAP when certain conditions or meta-data are found in a deployment. The Java EE 7 APIs supplied with JBoss EAP are examples of modules that are added by detection of implicit dependencies in deployments.

Deployments can also be configured to exclude specific implicit dependencies by using the jboss-deployment-structure.xml deployment descriptor file. This can be useful when an application bundles a specific version of a library that JBoss EAP will attempt to add as an implicit dependency.

See the Add an Explicit Module Dependency to a Deployment section for details on using the jboss-deployment-structure.xml deployment descriptor.

Optional Dependencies

Explicit dependencies can be specified as optional. Failure to load an optional dependency will not cause a module to fail to load. However, if the dependency becomes available later it will not be added to the module’s class path. Dependencies must be available when the module is loaded.

Export a Dependency

A module’s class path contains only its own classes and that of its immediate dependencies. A module is not able to access the classes of the dependencies of one of its dependencies. However, a module can specify that an explicit dependency is exported. An exported dependency is provided to any module that depends on the module that exports it.

For example, Module A depends on Module B, and Module B depends on Module C. Module A can access the classes of Module B, and Module B can access the classes of Module C. Module A cannot access the classes of Module C unless:

  • Module A declares an explicit dependency on Module C, or
  • Module B exports its dependency on Module C.
Global Modules

A global module is a module that JBoss EAP provides as a dependency to every application. Any module can be made global by adding it to JBoss EAP’s list of global modules. It does not require changes to the module.

See the Define Global Modules section of the JBoss EAP Configuration Guide for details.

3.1.3.1. Display Module Dependencies Using the Management CLI

You can use the following management operation to view information about a particular module and its dependencies:

/core-service=module-loading:module-info(name=$MODULE_NAME)

Example of module-info output

[standalone@localhost:9990 /] /core-service=module-loading:module-info(name=org.jboss.logmanager
{
    "outcome" => "success",
    "result" => {
        "name" => "org.jboss.logmanager:main",
        "main-class" => undefined,
        "fallback-loader" => undefined,
        "dependencies" => [
            {
                "dependency-name" => "ModuleDependency",
                "module-name" => "javax.api:main",
                "export-filter" => "Reject",
                "import-filter" => "multi-path filter {exclude children of \"META-INF/\", exclude equals \"META-INF\", default accept}",
                "optional" => false
            },
            {
                "dependency-name" => "ModuleDependency",
                "module-name" => "org.jboss.modules:main",
                "export-filter" => "Reject",
                "import-filter" => "multi-path filter {exclude children of \"META-INF/\", exclude equals \"META-INF\", default accept}",
                "optional" => false
            }
        ],
        "local-loader-class" => undefined,
        "resource-loaders" => [
            {
                "type" => "org.jboss.modules.JarFileResourceLoader",
                "paths" => [
                    "",
                    "org/jboss/logmanager",
                    "META-INF/services",
                    "org",
                    "META-INF/maven/org.jboss.logmanager/jboss-logmanager",
                    "org/jboss",
                    "org/jboss/logmanager/errormanager",
                    "org/jboss/logmanager/formatters",
                    "META-INF",
                    "org/jboss/logmanager/filters",
                    "org/jboss/logmanager/config",
                    "META-INF/maven",
                    "org/jboss/logmanager/handlers",
                    "META-INF/maven/org.jboss.logmanager"
                ]
            },
            {
                "type" => "org.jboss.modules.NativeLibraryResourceLoader",
                "paths" => undefined
            }
        ]
    }
}

3.1.4. Class Loading in Deployments

For the purposes of class loading, JBoss EAP treats all deployments as modules. These are called dynamic modules. Class loading behavior varies according to the deployment type.

WAR Deployment
A WAR deployment is considered to be a single module. Classes in the WEB-INF/lib directory are treated the same as classes in the WEB-INF/classes directory. All classes packaged in the WAR will be loaded with the same class loader.
EAR Deployment

EAR deployments are made up of more than one module, and are defined by the following rules:

  1. The lib/ directory of the EAR is a single module called the parent module.
  2. Each WAR deployment within the EAR is a single module.
  3. Each EJB JAR deployment within the EAR is a single module.

Subdeployment modules (the WAR and JAR deployments within the EAR) have an automatic dependency on the parent module. However, they do not have automatic dependencies on each other. This is called subdeployment isolation, and can be disabled per deployment, or for the entire application server.

Explicit dependencies between subdeployment modules can be added by the same means as any other module.

3.1.5. Class Loading Precedence

The JBoss EAP modular class loader uses a precedence system to prevent class loading conflicts.

During deployment, a complete list of packages and classes is created for each deployment and each of its dependencies. The list is ordered according to the class loading precedence rules. When loading classes at runtime, the class loader searches this list, and loads the first match. This prevents multiple copies of the same classes and packages within the deployments class path from conflicting with each other.

The class loader loads classes in the following order, from highest to lowest:

  1. Implicit dependencies: These dependencies are automatically added by JBoss EAP, such as the JAVA EE APIs. These dependencies have the highest class loader precedence because they contain common functionality and APIs that are supplied by JBoss EAP.

    Refer to Implicit Module Dependencies for complete details about each implicit dependency.

  2. Explicit dependencies: These dependencies are manually added to the application configuration using the application’s MANIFEST.MF file or the new optional JBoss deployment descriptor jboss-deployment-structure.xml file.

    Refer to Add an Explicit Module Dependency to a Deployment to learn how to add explicit dependencies.

  3. Local resources: These are class files packaged up inside the deployment itself, e.g. from the WEB-INF/classes or WEB-INF/lib directories of a WAR file.
  4. Inter-deployment dependencies: These are dependencies on other deployments in a EAR deployment. This can include classes in the lib directory of the EAR or classes defined in other EJB jars.

3.1.6. Dynamic Module Naming Conventions

JBoss EAP loads all deployments as modules, which are named according to the following conventions.

  • Deployments of WAR and JAR files are named using the following format:

    deployment.DEPLOYMENT_NAME

    For example, inventory.war and store.jar will have the module names of deployment.inventory.war and deployment.store.jar respectively.

  • Subdeployments within an Enterprise Archive (EAR) are named using the following format:

    deployment.EAR_NAME.SUBDEPLOYMENT_NAME

    For example, the subdeployment of reports.war within the enterprise archive accounts.ear will have the module name of deployment.accounts.ear.reports.war.

3.1.7. jboss-deployment-structure.xml

jboss-deployment-structure.xml is an optional deployment descriptor for JBoss EAP. This deployment descriptor provides control over class loading in the deployment.

The XML schema for this deployment descriptor is in /docs/schema/jboss-deployment-structure-1_2.xsd

3.2. Add an Explicit Module Dependency to a Deployment

Explicit module dependencies can be added to applications to add the classes of those modules to the class path of the application at deployment.

Note

JBoss EAP automatically adds some dependencies to deployments. See Implicit Module Dependencies for details.

Prerequisites

  1. A working software project that you want to add a module dependency to.
  2. You must know the name of the module being added as a dependency. See Included Modules for the list of static modules included with JBoss EAP. If the module is another deployment then see Dynamic Module Naming to determine the module name.

Dependencies can be configured using two methods:

  • Adding entries to the MANIFEST.MF file of the deployment.
  • Adding entries to the jboss-deployment-structure.xml deployment descriptor.

Add a Dependency Configuration to MANIFEST.MF

Maven projects can be configured to create the required dependency entries in the MANIFEST.MF file.

  1. If the project does not have one, create a file called MANIFEST.MF. For a web application (WAR) add this file to the META-INF directory. For an EJB archive (JAR) add it to the META-INF directory.
  2. Add a dependencies entry to the MANIFEST.MF file with a comma-separated list of dependency module names:

    Dependencies: org.javassist, org.apache.velocity, org.antlr
    • To make a dependency optional, append optional to the module name in the dependency entry:

      Dependencies: org.javassist optional, org.apache.velocity
    • A dependency can be exported by appending export to the module name in the dependency entry:

      Dependencies: org.javassist, org.apache.velocity export
    • The annotations flag is needed when the module dependency contains annotations that need to be processed during annotation scanning, such as when declaring EJB interceptors. Without this, an EJB interceptor declared in a module cannot be used in a deployment. There are other situations involving annotation scanning when this is needed too.

      Dependencies: org.javassist, test.module annotations
    • By default items in the META-INF of a dependency are not accessible. The services dependency makes items from META-INF/services accessible so that services in the modules can be loaded.

      Dependencies: org.javassist, org.hibernate services
    • To scan a beans.xml file and make its resulting beans available to the application, the meta-inf dependency can be used.

      Dependencies: org.javassist, test.module meta-inf

Add a Dependency Configuration to the jboss-deployment-structure.xml

  1. If the application does not have one, create a new file called jboss-deployment-structure.xml and add it to the project. This file is an XML file with the root element of <jboss-deployment-structure>.

    <jboss-deployment-structure>
    
    </jboss-deployment-structure>

    For a web application (WAR) add this file to the WEB-INF directory. For an EJB archive (JAR) add it to the META-INF directory.

  2. Create a <deployment> element within the document root and a <dependencies> element within that.
  3. Within the <dependencies> node, add a module element for each module dependency. Set the name attribute to the name of the module.

    <module name="org.javassist" />
    • A dependency can be made optional by adding the optional attribute to the module entry with the value of true. The default value for this attribute is false.

      <module name="org.javassist" optional="true" />
    • A dependency can be exported by adding the export attribute to the module entry with the value of true. The default value for this attribute is false.

      <module name="org.javassist" export="true" />
    • When the module dependency contains annotations that need to be processed during annotation scanning, the annotations flag is used.

      <module name="test.module" annotations="true" />
    • The Services dependency specifies whether and how services found in this dependency are used. The default is none. Specifying a value of import for this attribute is equivalent to adding a filter at the end of the import filter list which includes the META-INF/services path from the dependency module. Setting a value of export for this attribute is equivalent to the same action on the export filter list.

      <module name="org.hibernate" services="import" />
    • The META-INF dependency specifies whether and how META-INF entries in this dependency are used. The default is none. Specifying a value of import for this attribute is equivalent to adding a filter at the end of the import filter list which includes the META-INF/** path from the dependency module. Setting a value of export for this attribute is equivalent to the same action on the export filter list.

      <module name="test.module" meta-inf="import" />

Example: jboss-deployment-structure.xml with two dependencies

<jboss-deployment-structure>
   <deployment>
      <dependencies>
         <module name="org.javassist" />
         <module name="org.apache.velocity" export="true" />
      </dependencies>
   </deployment>
</jboss-deployment-structure>

JBoss EAP adds the classes from the specified modules to the class path of the application when it is deployed.

Creating a Jandex Index

The annotations flag requires that the module contain a Jandex index. In JBoss EAP 7.0, this is generated automatically. However, to add the index manually, perhaps for backwards compatibility, create a new "index JAR" to add to the module. Use the Jandex JAR to build the index, and then insert it into a new JAR file.

Creating a Jandex index::

  1. Create the index:

    java -jar modules/system/layers/base/org/jboss/jandex/main/jandex-jandex-2.0.0.Final-redhat-1.jar $JAR_FILE
  2. Create a temporary working space:

    mkdir /tmp/META-INF
  3. Move the index file to the working directory

    mv $JAR_FILE.ifx /tmp/META-INF/jandex.idx
    1. Option 1: Include the index in a new JAR file

      jar cf index.jar -C /tmp META-INF/jandex.idx

      Then place the JAR in the module directory and edit module.xml to add it to the resource roots.

    2. Option 2: Add the index to an existing JAR

      java -jar /modules/org/jboss/jandex/main/jandex-1.0.3.Final-redhat-1.jar -m $JAR_FILE
  4. Tell the module import to utilize the annotation index, so that annotation scanning can find the annotations.

    1. Option 1: If you are adding a module dependency using MANIFEST.MF, add annotations after the module name. For example change:

      Dependencies: test.module, other.module

      to

      Dependencies: test.module annotations, other.module
    2. Option 2: If you are adding a module dependency using jboss-deployment-structure.xml add annotations="true" on the module dependency.

      Note

      An annotation index is required when an application wants to use annotated Java EE components defined in classes within the static module. In JBoss EAP 7.0, annotation indexes for static modules are automatically generated, so you do not need to create them. However, you must tell the module import to use the annotations by adding the dependencies to either the MANIFEST.MF or the jboss-deployment-structure.xml file.

3.3. Generate MANIFEST.MF entries using Maven

Maven projects using the Maven JAR, EJB, or WAR packaging plug-ins can generate a MANIFEST.MF file with a Dependencies entry. This does not automatically generate the list of dependencies, but only creates the MANIFEST.MF file with the details specified in the pom.xml.

Before generating the MANIFEST.MF entries using Maven, you will require:

  • A working Maven project, which is using one of the JAR, EJB, or WAR plug-ins (maven-jar-plugin, maven-ejb-plugin, or maven-war-plugin).
  • You must know the name of the project’s module dependencies. Refer to Included Modules for the list of static modules included with JBoss EAP. If the module is another deployment, then refer to Dynamic Module Naming to determine the module name.

Generate a MANIFEST.MF File Containing Module Dependencies

  1. Add the following configuration to the packaging plug-in configuration in the project’s pom.xml file.

    <configuration>
       <archive>
          <manifestEntries>
             <Dependencies></Dependencies>
          </manifestEntries>
       </archive>
    </configuration>
  2. Add the list of module dependencies to the <Dependencies> element. Use the same format that is used when adding the dependencies to the MANIFEST.MF file:

    <Dependencies>org.javassist, org.apache.velocity</Dependencies>

    The optional and export attributes can also be used here:

    <Dependencies>org.javassist optional, org.apache.velocity export</Dependencies>
  3. Build the project using the Maven assembly goal:

    [Localhost ]$ mvn assembly:single

    When the project is built using the assembly goal, the final archive contains a MANIFEST.MF file with the specified module dependencies.

    Example: Configured Module Dependencies in pom.xml

    Note

    The example here shows the WAR plug-in but it also works with the JAR and EJB plug-ins (maven-jar-plugin and maven-ejb-plugin).

    <plugins>
       <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-war-plugin</artifactId>
          <configuration>
             <archive>
                <manifestEntries>
                   <Dependencies>org.javassist, org.apache.velocity</Dependencies>
                </manifestEntries>
             </archive>
          </configuration>
       </plugin>
    </plugins>

3.4. Prevent a Module Being Implicitly Loaded

You can configure a deployable application to prevent implicit dependencies from being loaded. This can be useful when an application includes a different version of a library or framework than the one that will be provided by the application server as an implicit dependency.

Prerequisites

  • A working software project that you want to exclude an implicit dependency from.
  • You must know the name of the module to exclude. Refer to Implicit Module Dependencies for a list of implicit dependencies and their conditions.

Add dependency exclusion configuration to jboss-deployment-structure.xml

  1. If the application does not have one, create a new file called jboss-deployment-structure.xml and add it to the project. This is an XML file with the root element of <jboss-deployment-structure>.

    <jboss-deployment-structure>
    
    </jboss-deployment-structure>

    For a web application (WAR) add this file to the WEB-INF directory. For an EJB archive (JAR) add it to the META-INF directory.

  2. Create a <deployment> element within the document root and an <exclusions> element within that.

    <deployment>
       <exclusions>
    
       </exclusions>
    </deployment>
  3. Within the exclusions element, add a <module> element for each module to be excluded. Set the name attribute to the name of the module.

    <module name="org.javassist" />

    Example: Excluding two modules

    <jboss-deployment-structure>
       <deployment>
          <exclusions>
             <module name="org.javassist" />
             <module name="org.dom4j" />
          </exclusions>
       </deployment>
    </jboss-deployment-structure>

3.5. Exclude a Subsystem from a Deployment

Excluding a subsystem provides the same effect as removing the subsystem, but it applies only to a single deployment. You can exclude a subsystem from a deployment by editing the jboss-deployment-structure.xml configuration file.

Exclude a Subsystem

  1. Edit the jboss-deployment-structure.xml file.
  2. Add the following XML inside the <deployment> tags:

    <exclude-subsystems>
      <subsystem name="SUBSYSTEM_NAME" />
    </exclude-subsystems>
  3. Save the jboss-deployment-structure.xml file.

The subsystem’s deployment unit processors will no longer run on the deployment.

Example: Example jboss-deployment-structure.xml file

<jboss-deployment-structure xmlns="urn:jboss:deployment-structure:1.2">
  <ear-subdeployments-isolated>true</ear-subdeployments-isolated>
  <deployment>
    <exclude-subsystems>
      <subsystem name="jaxrs" />
    </exclude-subsystems>
    <exclusions>
      <module name="org.javassist" />
    </exclusions>
    <dependencies>
      <module name="deployment.javassist.proxy" />
      <module name="deployment.myjavassist" />
      <module name="myservicemodule" services="import"/>
    </dependencies>
    <resources>
      <resource-root path="my-library.jar" />
    </resources>
  </deployment>
  <sub-deployment name="myapp.war">
    <dependencies>
      <module name="deployment.myear.ear.myejbjar.jar" />
    </dependencies>
    <local-last value="true" />
  </sub-deployment>
  <module name="deployment.myjavassist" >
    <resources>
     <resource-root path="javassist.jar" >
       <filter>
         <exclude path="javassist/util/proxy" />
       </filter>
     </resource-root>
    </resources>
  </module>
  <module name="deployment.javassist.proxy" >
    <dependencies>
      <module name="org.javassist" >
        <imports>
          <include path="javassist/util/proxy" />
          <exclude path="/**" />
        </imports>
      </module>
    </dependencies>
  </module>
</jboss-deployment-structure>

3.6. Use the Class Loader Programmatically in a Deployment

3.6.1. Programmatically Load Classes and Resources in a Deployment

You can programmatically find or load classes and resources in your application code. The method you choose will depend on a number of factors. This topic describes the methods available and provides guidelines for when to use them.

Load a Class Using the Class.forName() Method

You can use the Class.forName() method to programmatically load and initialize classes. This method has two signatures:

  • Class.forName(String className): This signature takes only one parameter, the name of the class you need to load. With this method signature, the class is loaded by the class loader of the current class and initializes the newly loaded class by default.
  • Class.forName(String className, boolean initialize, ClassLoader loader): This signature expects three parameters: the class name, a boolean value that specifies whether to initialize the class, and the ClassLoader that should load the class.

The three argument signature is the recommended way to programmatically load a class. This signature allows you to control whether you want the target class to be initialized upon load. It is also more efficient to obtain and provide the class loader because the JVM does not need to examine the call stack to determine which class loader to use. Assuming the class containing the code is named CurrentClass, you can obtain the class’s class loader using CurrentClass.class.getClassLoader() method.

Example: Provide a class loader to load and initialize the TargetClass

The following example provides the class loader to load and initialize the TargetClass class:

Class<?> targetClass = Class.forName("com.myorg.util.TargetClass", true, CurrentClass.class.getClassLoader());

Find All Resources with a Given Name

If you know the name and path of a resource, the best way to load it directly is to use the standard Java development kit Class or ClassLoader API.

  • Load a Single Resource: To load a single resource located in the same directory as your class or another class in your deployment, you can use the Class.getResourceAsStream() method.

    InputStream inputStream = CurrentClass.class.getResourceAsStream("targetResourceName");
  • Load All Instances of a Single Resource: To load all instances of a single resource that are visible to your deployment’s class loader, use the Class.getClassLoader().getResources(String resourceName) method, where resourceName is the fully qualified path of the resource. This method returns an Enumeration of all URL objects for resources accessible by the class loader with the given name. You can then iterate through the array of URLs to open each stream using the openStream() method.

    Example: Load all instances of a resource and iterate through the result

    Enumeration<URL> urls = CurrentClass.class.getClassLoader().getResources("full/path/to/resource");
    while (urls.hasMoreElements()) {
        URL url = urls.nextElement();
        InputStream inputStream = null;
        try {
            inputStream = url.openStream();
            // Process the inputStream
            ...
        } catch(IOException ioException) {
            // Handle the error
        } finally {
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (Exception e) {
                    // ignore
                }
            }
        }
    }

Because the URL instances are loaded from local storage, it is not necessary to use the openConnection() or other related methods. Streams are much simpler to use and minimize the complexity of the code.

  • Load a Class File From the Class Loader: If a class has already been loaded, you can load the class file that corresponds to that class using the following syntax:

    Example: Load a class file for a class that has been loaded

    InputStream inputStream = CurrentClass.class.getResourceAsStream(TargetClass.class.getSimpleName() + ".class");

    If the class is not yet loaded, you must use the class loader and translate the path:

    Example: Load a class file for a class that has not been loaded

    String className = "com.myorg.util.TargetClass"
    InputStream inputStream = CurrentClass.class.getClassLoader().getResourceAsStream(className.replace('.', '/') + ".class");

3.6.2. Programmatically Iterate Resources in a Deployment

The JBoss Modules library provides several APIs for iterating all deployment resources. The JavaDoc for the JBoss Modules API is located here: http://docs.jboss.org/jbossmodules/1.3.0.Final/api/. To use these APIs, you must add the following dependency to the MANIFEST.MF:

Dependencies: org.jboss.modules

It is important to note that while these APIs provide increased flexibility, they will also run much more slowly than a direct path lookup.

This topic describes some of the ways you can programmatically iterate through resources in your application code.

  • List Resources Within a Deployment and Within All Imports: There are times when it is not possible to look up resources by the exact path. For example, the exact path may not be known or you may need to examine more than one file in a given path. In this case, the JBoss Modules library provides several APIs for iterating all deployment resources. You can iterate through resources in a deployment by utilizing one of two methods.

    • Iterate All Resources Found in a Single Module: The ModuleClassLoader.iterateResources() method iterates all the resources within this module class loader. This method takes two arguments: the starting directory name to search and a boolean that specifies whether it should recurse into subdirectories.

      The following example demonstrates how to obtain the ModuleClassLoader and obtain the iterator for resources in the bin/ directory, recursing into subdirectories.

Example: Find resources in the "bin" directory, recursing into subdirectories

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Iterator<Resource> mclResources = moduleClassLoader.iterateResources("bin",true);

The resultant iterator may be used to examine each matching resource and query its name and size (if available), open a readable stream, or acquire a URL for the resource.

  • Iterate All Resources Found in a Single Module and Imported Resources: The Module.iterateResources() method iterates all the resources within this module class loader, including the resources that are imported into the module. This method returns a much larger set than the previous method. This method requires an argument, which is a filter that narrows the result to a specific pattern. Alternatively, PathFilters.acceptAll() can be supplied to return the entire set.

Example: Find the entire set of resources in this module, including imports

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Module module = moduleClassLoader.getModule();
Iterator<Resource> moduleResources = module.iterateResources(PathFilters.acceptAll());
  • Find All Resources That Match a Pattern: If you need to find only specific resources within your deployment or within your deployment’s full import set, you need to filter the resource iteration. The JBoss Modules filtering APIs give you several tools to accomplish this.

    • Examine the Full Set of Dependencies: If you need to examine the full set of dependencies, you can use the Module.iterateResources() method’s PathFilter parameter to check the name of each resource for a match.
    • Examine Deployment Dependencies: If you need to look only within the deployment, use the ModuleClassLoader.iterateResources() method. However, you must use additional methods to filter the resultant iterator. The PathFilters.filtered() method can provide a filtered view of a resource iterator this case. The PathFilters class includes many static methods to create and compose filters that perform various functions, including finding child paths or exact matches, or matching an Ant-style "glob" pattern.
  • Additional Code Examples For Filtering Resouces: The following examples demonstrate how to filter resources based on different criteria.

Example: Find all files named "messages.properties" in your deployment

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Iterator<Resource> mclResources = PathFilters.filtered(PathFilters.match("**/messages.properties"), moduleClassLoader.iterateResources("", true));

Example: Find all files named "messages.properties" in your deployment and imports

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Module module = moduleClassLoader.getModule();
Iterator<Resource> moduleResources = module.iterateResources(PathFilters.match("**/message.properties"));

Example: Find all files inside any directory named "my-resources" in your deployment

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Iterator<Resource> mclResources = PathFilters.filtered(PathFilters.match("**/my-resources/**"), moduleClassLoader.iterateResources("", true));

Example: Find all files named "messages" or "errors" in your deployment and imports

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Module module = moduleClassLoader.getModule();
Iterator<Resource> moduleResources = module.iterateResources(PathFilters.any(PathFilters.match("**/messages"), PathFilters.match("**/errors"));

Example: Find all files in a specific package in your deployment

ModuleClassLoader moduleClassLoader = (ModuleClassLoader) TargetClass.class.getClassLoader();
Iterator<Resource> mclResources = moduleClassLoader.iterateResources("path/form/of/packagename", false);

3.7. Class Loading and Subdeployments

3.7.1. Modules and Class Loading in Enterprise Archives

Enterprise Archives (EAR) are not loaded as a single module like JAR or WAR deployments. They are loaded as multiple unique modules.

The following rules determine what modules exist in an EAR:

  • The contents of the lib/ directory in the root of the EAR archive is a module. This is called the parent module.
  • Each WAR and EJB JAR subdeployment is a module. These modules have the same behavior as any other module as well as implicit dependencies on the parent module.
  • Subdeployments have implicit dependencies on the parent module and any other non-WAR subdeployments.

The implicit dependencies on non-WAR subdeployments occur because JBoss EAP has subdeployment class loader isolation disabled by default. Dependencies on the parent module persist, regardless of subdeployment class loader isolation.

Important

No subdeployment ever gains an implicit dependency on a WAR subdeployment. Any subdeployment can be configured with explicit dependencies on another subdeployment as would be done for any other module.

Subdeployment class loader isolation can be enabled if strict compatibility is required. This can be enabled for a single EAR deployment or for all EAR deployments. The Java EE specification recommends that portable applications should not rely on subdeployments being able to access each other unless dependencies are explicitly declared as Class-Path entries in the MANIFEST.MF file of each subdeployment.

3.7.2. Subdeployment Class Loader Isolation

Each subdeployment in an Enterprise Archive (EAR) is a dynamic module with its own class loader. By default a subdeployment can access the resources of other subdeployments.

If a subdeployment is not to be allowed to access the resources of other subdeployments, strict subdeployment isolation can be enabled.

3.7.3. Enable Subdeployment Class Loader Isolation Within a EAR

This task shows you how to enable subdeployment class loader isolation in an EAR deployment by using a special deployment descriptor in the EAR. This does not require any changes to be made to the application server and does not affect any other deployments.

Important

Even when subdeployment class loader isolation is disabled it is not possible to add a WAR deployment as a dependency.

  1. Add the deployment descriptor file: Add the jboss-deployment-structure.xml deployment descriptor file to the META-INF directory of the EAR if it doesn’t already exist and add the following content:

    <jboss-deployment-structure>
    
    </jboss-deployment-structure>
  2. Add the <ear-subdeployments-isolated> element: Add the <ear-subdeployments-isolated> element to the jboss-deployment-structure.xml file if it doesn’t already exist with the content of true.

    <ear-subdeployments-isolated>true</ear-subdeployments-isolated>

Result

Subdeployment class loader isolation will now be enabled for this EAR deployment. This means that the subdeployments of the EAR will not have automatic dependencies on each of the non-WAR subdeployments.

3.7.4. Configuring Session Sharing between Subdeployments in Enterprise Archives

JBoss EAP provides the ability to configure enterprise archives (EARs) to share sessions between WAR module subdeployments contained in the EAR. This functionality is disabled by default and must be explicitly enabled in the META-INF/jboss-all.xml file in the EAR.

Important

Since this feature is not a standard servlet feature, your applications may not be portable if this functionality is enabled.

To enable session sharing between WARs within an EAR, you need to declare a shared-session-config element in the META-INF/jboss-all.xml of the EAR:

Example META-INF/jboss-all.xml

<jboss umlns="urn:jboss:1.0">
  ...
  <shared-session-config xmlns="urn:jboss:shared-session-config:1.0">
  </shared-session-config>
  ...
</jboss>

The shared-session-config element is used to configure the shared session manager for all WARs within the EAR. If the shared-session-config element is present, all WARs within the EAR will share the same session manager. Changes made here will affect all WARs contained within the EAR.

3.7.4.1. Reference of Shared Session Config Options

The shared-session-config element has the following structure:

  • shared-session-config

    • max-active-sessions
    • session-config

      • session-timeout
      • cookie-config

        • name
        • domain
        • path
        • comment
        • http-only
        • secure
        • max-age
      • tracking-mode
    • replication-config

      • cache-name
      • replication-granularity

Example META-INF/jboss-all.xml

<jboss umlns="urn:jboss:1.0">
  <shared-session-config xmlns="urn:jboss:shared-session-config:1.0">
    <max-active-sessions>10</max-active-sessions>
    <session-config>
      <session-timeout>0</session-timeout>
      <cookie-config>
        <name>JSESSIONID</name>
        <domain>domainName</domain>
        <path>/cookiePath</path>
        <comment>cookie comment</comment>
        <http-only>true</http-only>
        <secure>true</secure>
        <max-age>-1</max-age>
      </cookie-config>
    </session-config>
    <tracking-mode>COOKIE</tracking-mode>
  </shared-session-config>
  <replication-config>
    <cache-name>web</cache-name>
    <replication-granularity>SESSION</replication-granularity>
  </replication-config>
</jboss>

shared-session-config

Root element for the shared session configuration. If this is present in the META-INF/jboss-all.xml then all deployed WARs contained in the EAR will share a single session manager.

max-active-sessions

Number of maximum sessions allowed.

session-config

Contains the session configuration parameters for all deployed WARs contained in the EAR.

session-timeout

Defines the default session timeout interval for all sessions created in the deployed WARs contained in the EAR. The specified timeout must be expressed in a whole number of minutes. If the timeout is 0 or less, the container ensures the default behavior of sessions is to never time out. If this element is not specified, the container must set its default timeout period.

cookie-config

Contains the configuration of the session tracking cookies created by the deployed WARs contained in the EAR.

name

The name that will be assigned to any session tracking cookies created by the deployed WARs contained in the EAR. The default is JSESSIONID.

domain

The domain name that will be assigned to any session tracking cookies created by the deployed WARs contained in the EAR.

path

The path that will be assigned to any session tracking cookies created by the deployed WARs contained in the EAR.

comment

The comment that will be assigned to any session tracking cookies created by the deployed WARs contained in the EAR.

http-only

Specifies whether any session tracking cookies created by the deployed WARs contained in the EAR will be marked as HttpOnly.

secure

Specifies whether any session tracking cookies created by the deployed WARs contained in the EAR will be marked as secure even if the request that initiated the corresponding session is using plain HTTP instead of HTTPS

max-age

The lifetime (in seconds) that will be assigned to any session tracking cookies created by the deployed WARs contained in the EAR. Default is -1.

tracking-mode

Defines the tracking modes for sessions created by the deployed WARs contained in the EAR.

replication-config

Contains the HTTP session clustering configuration.

cache-name

This option is for use in clustering only. It specifies the name of the Infinispan container and cache in which to store session data. The default value, if not explicitly set, is determined by the application server. To use a specific cache within a cache container, use the form container.cache, for example web.dist. If name is unqualified, the default cache of the specified container is used.

replication-granularity

This option is for use in clustering only. It determines the session replication granularity level. The possible values are SESSION and ATTRIBUTE with SESSION being the default.

If SESSION granularity is used, all session attributes are replicated if any were modified within the scope of a request. This policy is required if an object reference is shared by multiple session attributes. However, this can be inefficient if session attributes are sufficiently large and/or are modified infrequently, since all attributes must be replicated regardless of whether they were modified or not.

If ATTRIBUTE granularity is used, only those attributes that were modified within the scope of a request are replicated. This policy is not appropriate if an object reference is shared by multiple session attributes. This can be more efficient than SESSION granularity if the session attributes are sufficiently large and/or are modified infrequently.

3.8. Deploy Tag Library Descriptors (TLDs) in a Custom Module

If you have multiple applications that use common Tag Library Descriptors (TLDs), it may be useful to separate the TLDs from the applications so that they are located in one central and unique location. This enables easier additions and updates to TLDs without necessarily having to update each individual application that uses them.

This can be done by creating a custom JBoss EAP module that contains the TLD JARs, and declaring a dependency on that module in the applications.

Note

Ensure that at least one JAR contains TLDs and the TLDs are packed in META-INF.

Deploy TLDs in a Custom Module

  1. Using the management CLI, connect to your JBoss EAP instance and execute the following command to create the custom module containing the TLD JAR:

    module add --name=MyTagLibs --resources=/path/to/TLDarchive.jar
    Important

    Using the module management CLI command to add and remove modules is provided as technology preview only. This command is not appropriate for use in a managed domain or when connecting to the management CLI remotely. Modules should be added and removed manually in a production environment. For more information, see the Create a Custom Module Manually and Remove a Custom Module Manually sections of the JBoss EAP Configuration Guide.

    If the TLDs are packaged with classes that require dependencies, use the --dependencies= option to ensure that you specify those dependencies when creating the custom module.

    When creating the module, you can specify multiple JAR resources by separating each one with the file system-specific separator for your system.

    • For linux - :. Example, --resources=<path-to-jar>:<path-to-another-jar>
    • For Windows - ;. Example, --resources=<path-to-jar>;<path-to-another-jar>

      Note
      --resources
      It is required unless --module-xml is used. It lists file system paths, usually JAR files, separated by a file system-specific path separator, for example java.io.File.pathSeparatorChar. The files specified will be copied to the created module’s directory.
      --resource-delimiter
      It is an optional user-defined path separator for the resources argument. If this argument is present, the command parser will use the value here instead of the file system-specific path separator. This allows the modules command to be used in cross-platform scripts.
  2. In your applications, declare a dependency on the new MyTagLibs custom module using one of the methods described in Add an Explicit Module Dependency to a Deployment.
Important

Ensure that you also import META-INF when declaring the dependency. For example, for MANIFEST.MF:

Dependencies: com.MyTagLibs meta-inf

Or, for jboss-deployment-structure.xml, use the meta-inf attribute.

3.9. Reference

3.9.1. Implicit Module Dependencies

The following table lists the modules that are automatically added to deployments as dependencies and the conditions that trigger the dependency.

Table 3.1. Implicit Module Dependencies

Subsystem Responsible for Adding the DependencyPackage Dependencies That Are Always AddedPackage Dependencies That Are Conditionally AddedConditions That Trigger the Addition of the Dependency

Application Client

  • org.omg.api
  • org.jboss.xnio
  

Batch

  • javax.batch.api
  • org.jberet.jberet-core
  • org.wildfly.jberet
  

Bean Validation

  • org.hibernate.validator
  • javax.validation.api
  

Core Server

  • javax.api
  • sun.jdk
  • org.jboss.vfs
  • ibm.jdk
  

DriverDependenciesProcessor

 
  • javax.transaction.api
 

EE

  • org.jboss.invocation (except org.jboss.invocation.proxy.classloading)
  • org.jboss.as.ee (except org.jboss.as.ee.component.serialization, org.jboss.as.ee.concurrent, org.jboss.as.ee.concurrent.handle)
  • org.wildfly.naming
  • javax.annotation.api
  • javax.enterprise.concurrent.api
  • javax.interceptor.api
  • javax.json.api
  • javax.resource.api
  • javax.rmi.api
  • javax.xml.bind.api
  • javax.api
  • org.glassfish.javax.el
  • org.glassfish.javax.enterprise.concurrent
  

EJB 3

  • javax.ejb.api
  • javax.xml.rpc.api
  • org.jboss.ejb-client
  • org.jboss.iiop-client
  • org.jboss.as.ejb3
  • org.wildfly.iiop-openjdk
 

IIOP

  • org.omg.api
  • javax.rmi.api
  • javax.orb.api
  

JAX-RS (RESTEasy)

  • javax.xml.bind.api
  • javax.ws.rs.api
  • javax.json.api
  • org.jboss.resteasy.resteasy-atom-provider
  • org.jboss.resteasy.resteasy-crypto
  • org.jboss.resteasy.resteasy-validator-provider-11
  • org.jboss.resteasy.resteasy-jaxrs
  • org.jboss.resteasy.resteasy-jaxb-provider
  • org.jboss.resteasy.resteasy-jackson2-provider
  • org.jboss.resteasy.resteasy-jsapi
  • org.jboss.resteasy.resteasy-json-p-provider
  • org.jboss.resteasy.resteasy-multipart-provider
  • org.jboss.resteasy.resteasy-yaml-provider
  • org.codehaus.jackson.jackson-core-asl
  • org.jboss.resteasy.resteasy-cdi

The presence of JAX-RS annotations in the deployment.

JCA

  • javax.resource.api
  • javax.jms.api
  • javax.validation.api
  • org.jboss.ironjacamar.api
  • org.jboss.ironjacamar.impl
  • org.hibernate.validator

The deployment of a resource adapter (RAR) archive.

JPA (Hibernate)

  • javax.persistence.api
  • org.jboss.as.jpa
  • org.jboss.as.jpa.spi
  • org.javassist

The presence of an @PersistenceUnit or @PersistenceContext annotation, or a <persistence-unit-ref> or <persistence-context-ref> element in a deployment descriptor.

JBoss EAP maps persistence provider names to module names. If you name a specific provider in the persistence.xml file, a dependency is added for the appropriate module. If this not the desired behavior, you can exclude it using a jboss-deployment-structure.xml file.

JSF (Java Server Faces)

 
  • javax.faces.api
  • com.sun.jsf-impl
  • org.jboss.as.jsf
  • org.jboss.as.jsf-injection

Added to EAR applications.

Added to WAR applications only if the web.xml file does NOT specify a context-param of org.jboss.jbossfaces.WAR_BUNDLES_JSF_IMPL with a value of true.

JSR-77

  • javax.management.j2ee.api
  

Logging

  • org.jboss.logging
  • org.apache.commons.logging
  • org.apache.log4j
  • org.slf4j
  • org.jboss.logging.jul-to-slf4j-stub
  

Mail

  • javax.mail.api
  • javax.activation.api
  

Messaging

  • javax.jms.api
  • org.wildfly.extension.messaging-activemq
 

PicketLink Federation

 
  • org.picketlink
 

Pojo

  • org.jboss.as.pojo
  

SAR

 
  • org.jboss.modules
  • org.jboss.as.system-jmx
  • org.jboss.common-beans

The deployment of a SAR archive that has a jboss-service.xml.

Seam2

 
  • org.jboss.vfs

.

Security

  • org.picketbox
  • org.jboss.as.security
  • javax.security.jacc.api
  • javax.security.auth.message.api
  

ServiceActivator

 
  • org.jboss.msc
 

Transactions

  • javax.transaction.api
  • org.jboss.xts
  • org.jboss.jts
  • org.jboss.narayana.compensations
 

Undertow

  • javax.servlet.jstl.api
  • javax.servlet.api
  • javax.servlet.jsp.api
  • javax.websocket.api
  • io.undertow.core
  • io.undertow.servlet
  • io.undertow.jsp
  • io.undertow.websocket
  • io.undertow.js
  • org.wildfly.clustering.web.api
 

Web Services

  • javax.jws.api
  • javax.xml.soap.api
  • javax.xml.ws.api
  • org.jboss.ws.api
  • org.jboss.ws.spi

If it is not application client type, then it will add the conditional dependencies.

Weld (CDI)

  • javax.enterprise.api
  • javax.inject.api
  • javax.persistence.api
  • org.javassist
  • org.jboss.as.weld
  • org.jboss.weld.core
  • org.jboss.weld.probe
  • org.jboss.weld.api
  • org.jboss.weld.spi
  • org.hibernate.validator.cdi

The presence of a beans.xml file in the deployment.

3.9.2. Included Modules

For the complete listing of the included modules and whether they are supported, see Red Hat JBoss Enterprise Application Platform 7 Included Modules on the Red Hat Customer Portal.

3.9.3. JBoss Deployment Structure Deployment Descriptor Reference

The key tasks that can be performed using this deployment descriptor are:

  • Defining explicit module dependencies.
  • Preventing specific implicit dependencies from loading.
  • Defining additional modules from the resources of that deployment.
  • Changing the subdeployment isolation behavior in that EAR deployment.
  • Adding additional resource roots to a module in an EAR.

Chapter 4. Logging

4.1. About Logging

Logging is the practice of recording a series of messages from an application that provides a record (or log) of the application’s activities.

Log messages provide important information for developers when debugging an application and for system administrators maintaining applications in production.

Most modern Java logging frameworks also include details such as the exact time and the origin of the message.

4.1.1. Supported Application Logging Frameworks

JBoss LogManager supports the following logging frameworks:

JBoss LogManager supports the following APIs:

  • JBoss Logging
  • commons-logging
  • SLF4J
  • Log4j
  • java.util.logging

JBoss LogManager also supports the following SPIs:

  • java.util.logging Handler
  • Log4j Appender
Note

If you are using the Log4j API and a Log4J Appender, then Objects will be converted to string before being passed.

4.2. Logging with the JBoss Logging Framework

4.2.1. About JBoss Logging

JBoss Logging is the application logging framework that is included in JBoss EAP. It provides an easy way to add logging to an application. You add code to your application that uses the framework to send log messages in a defined format. When the application is deployed to an application server, these messages can be captured by the server and displayed or written to file according to the server’s configuration.

JBoss Logging provides the following features:

  • An innovative, easy-to-use typed logger. A typed logger is a logger interface annotated with org.jboss.logging.annotations.MessageLogger. For examples, see Creating Internationalized Loggers, Messages and Exceptions.
  • Full support for internationalization and localization. Translators work with message bundles in properties files while developers work with interfaces and annotations. For details, see Internationalization and Localization.
  • Build-time tooling to generate typed loggers for production and runtime generation of typed loggers for development.

4.2.2. Add Logging to an Application with JBoss Logging

This procedure demonstrates how to add logging to an application using JBoss Logging.

Important

If you use Maven to build your project, you must configure Maven to use the JBoss EAP Maven repository. For more information, see Configure the JBoss EAP Maven Repository.

  1. The JBoss Logging JAR files must be in the build path for your application.

    • If you build using Red Hat JBoss Developer Studio, select Properties from the Project menu, then select Targeted Runtimes and ensure the runtime for JBoss EAP is checked.
    • If you use Maven to build your project, make sure you add the jboss-logging dependency to your project’s pom.xml file for access to JBoss Logging framework:

      <dependency>
      	<groupId>org.jboss.logging</groupId>
      	<artifactId>jboss-logging</artifactId>
      	<version>3.3.0.Final-redhat-1</version>
      	<scope>provided</scope>
      </dependency>

      The jboss-javaee-7.0 BOM manages the version of jboss-logging. For more details, see Manage Project Dependencies. See the logging quickstart for a working example of logging in an application.

    You do not need to include the JARs in your built application because JBoss EAP provides them to deployed applications.

  2. For each class to which you want to add logging:

    1. Add the import statements for the JBoss Logging class namespaces that you will be using. At a minimum you will need the following import:

      import org.jboss.logging.Logger;
    2. Create an instance of org.jboss.logging.Logger and initialize it by calling the static method Logger.getLogger(Class). It is recommended to create this as a single instance variable for each class.

      private static final Logger LOGGER = Logger.getLogger(HelloWorld.class);
  3. Call the Logger object methods in your code where you want to send log messages.

    The Logger has many different methods with different parameters for different types of messages. Use the following methods to send a log message with the corresponding log level and the message parameter as a string:

    LOGGER.debug("This is a debugging message.");
    LOGGER.info("This is an informational message.");
    LOGGER.error("Configuration file not found.");
    LOGGER.trace("This is a trace message.");
    LOGGER.fatal("A fatal error occurred.");

    For the complete list of JBoss Logging methods, see the Logging API documentation.

JBoss Logging Example

The following example loads customized configuration for an application from a properties file. If the specified file is not found, an ERROR level log message is recorded.

import org.jboss.logging.Logger;
public class LocalSystemConfig
{
   private static final Logger LOGGER = Logger.getLogger(LocalSystemConfig.class);

   public Properties openCustomProperties(String configname) throws CustomConfigFileNotFoundException
   {
      Properties props = new Properties();
      try
      {
         LOGGER.info("Loading custom configuration from "+configname);
         props.load(new FileInputStream(configname));
      }
      catch(IOException e) //catch exception in case properties file does not exist
      {
         LOGGER.error("Custom configuration file ("+configname+") not found. Using defaults.");
         throw new CustomConfigFileNotFoundException(configname);
      }

      return props;
   }
}

4.3. Per-deployment Logging

Per-deployment logging allows a developer to configure the logging configuration for their application in advance. When the application is deployed, logging begins according to the defined configuration. The log files created through this configuration contain information only about the behavior of the application.

Note

If the per-deployment logging configuration is not done, the configuration from logging subsystem is used for all the applications as well as the server.

This approach has advantages and disadvantages over using system-wide logging. An advantage is that the administrator of the JBoss EAP instance does not need to configure any other logging than the server logging. A disadvantage is that the per-deployment logging configuration is read only on server startup, and so cannot be changed at runtime.

4.3.1. Add Per-deployment Logging to an Application

To configure per-deployment logging to an application, add the logging.properties configuration file to your deployment. This configuration file is recommended because it can be used with any logging facade where JBoss Log Manager is the underlying log manager.

The directory into which the configuration file is added depends on the deployment method:

  • For EAR deployments, copy the logging configuration file to the META-INF directory.
  • For WAR or JAR deployments, copy the logging configuration file to the WEB-INF/classes directory.
Note

If you are using Simple Logging Facade for Java (SLF4J) or Apache log4j, the logging.properties configuration file is suitable. If you are using Apache log4j appenders then the configuration file log4j.properties is required. The configuration file jboss-logging.properties is supported only for legacy deployments.

Configuring logging.properties

The logging.properties file is used when the server boots, until the logging subsystem is started. If the logging subsystem is not included in your configuration, then the server uses the configuration in this file as the logging configuration for the entire server.

JBoss Log Manager Configuration Options

Logger options

  • loggers=<category>[,<category>,…​] - Specify a comma-separated list of logger categories to be configured. Any categories not listed here will not be configured from the following properties.
  • logger.<category>.level=<level> - Specify the level for a category. The level can be one of the valid levels. If unspecified, the level of the nearest parent will be inherited.
  • logger.<category>.handlers=<handler>[,<handler>,…​] - Specify a comma-separated list of the handler names to be attached to this logger. The handlers must be configured in the same properties file.
  • logger.<category>.filter=<filter> - Specify a filter for a category.
  • logger.<category>.useParentHandlers=(true|false) - Specify whether log messages should cascade up to parent handlers. The default value is true.

Handler options

  • handler.<name>=<className> - Specify the class name of the handler to instantiate. This option is mandatory.
  • handler.<name>.level=<level> - Restrict the level of this handler. If unspecified, the default value of ALL is retained.
  • handler.<name>.encoding=<encoding> - Specify the character encoding, if it is supported by this handler type. If not specified, a handler-specific default is used.
  • handler.<name>.errorManager=<name> - Specify the name of the error manager to use. The error manager must be configured in the same properties file. If unspecified, no error manager is configured.
  • handler.<name>.filter=<name> - Specify a filter for a category. See the filter expressions for details on defining a filter.
  • handler.<name>.formatter=<name> - Specify the name of the formatter to use, if it is supported by this handler type. The formatter must be configured in the same properties file. If not specified, messages will not be logged for most handler types.
  • handler.<name>.properties=<property>[,<property>,…​] - Specify a list of JavaBean-style properties to additionally configure. A rudimentary type introspection is done to ascertain the appropriate conversion for the given property.
  • handler.<name>.constructorProperties=<property>[,<property>,…​] - Specify a list of properties that should be used as construction parameters. A rudimentary type introspection is done to ascertain the appropriate conversion for the given property.
  • handler.<name>.<property>=<value> - Set the value of the named property.

For further information, see Log Handler Attributes in the JBoss EAP Configuration Guide.

Error manager options

  • errorManager.<name>=<className> - Specify the class name of the error manager to instantiate. This option is mandatory.
  • errorManager.<name>.properties=<property>[,<property>,…​] - Specify a list of JavaBean-style properties to additionally configure. A rudimentary type introspection is done to ascertain the appropriate conversion for the given property.
  • errorManager.<name>.<property>=<value> - Set the value of the named property.

Formatter options

  • formatter.<name>=<className> - Specify the class name of the formatter to instantiate. This option is mandatory.
  • formatter.<name>.properties=<property>[,<property>,…​] - Specify a list of JavaBean-style properties to additionally configure. A rudimentary type introspection is done to ascertain the appropriate conversion for the given property.
  • formatter.<name>.constructorProperties=<property>[,<property>,…​] - Specify a list of properties that should be used as construction parameters. A rudimentary type introspection is done to ascertain the appropriate conversion for the given property.
  • formatter.<name>.<property>=<value> - Set the value of the named property.

The following example shows the minimal configuration for logging.properties file that will log to the console.

# Additional logger names to configure (root logger is always configured)
# loggers=

# Root logger level
logger.level=INFO

# Root logger handlers
logger.handlers=CONSOLE

# Console handler configuration
handler.CONSOLE=org.jboss.logmanager.handlers.ConsoleHandler
handler.CONSOLE.properties=autoFlush
handler.CONSOLE.autoFlush=true
handler.CONSOLE.formatter=PATTERN

# Formatter pattern configuration
formatter.PATTERN=org.jboss.logmanager.formatters.PatternFormatter
formatter.PATTERN.properties=pattern
formatter.PATTERN.pattern=%K{level}%d{HH:mm:ss,SSS} %-5p %C.%M(%L) [%c] %s%e%n

4.4. Logging Profiles

Logging profiles are independent sets of logging configurations that can be assigned to deployed applications. As with the regular logging subsystem, a logging profile can define handlers, categories, and a root logger, but it cannot refer to configurations in other profiles or the main logging subsystem. The design of logging profiles mimics the logging subsystem for ease of configuration.

Logging profiles allow administrators to create logging configurations that are specific to one or more applications without affecting any other logging configurations. Because each profile is defined in the server configuration, the logging configuration can be changed without requiring that the affected applications be redeployed. However, logging profiles cannot be configured using the management console. For more information, see Configure a Logging Profile in the JBoss EAP Configuration Guide.

Each logging profile can have:

  • A unique name (required)
  • Any number of log handlers
  • Any number of log categories
  • Up to one root logger

An application can specify a logging profile to use in its MANIFEST.MF file, using the Logging-Profile attribute.

4.4.1. Specify a Logging Profile in an Application

An application specifies the logging profile to use in its MANIFEST.MF file.

Note

You must know the name of the logging profile that has been set up on the server for this application to use.

To add a logging profile configuration to an application, edit the MANIFEST.MF file.

  • If your application does not have a MANIFEST.MF file, create one with the following content to specify the logging profile name.

    Manifest-Version: 1.0
    Logging-Profile: LOGGING_PROFILE_NAME
  • If your application already has a MANIFEST.MF file, add the following line to specify the logging profile name.

    Logging-Profile: LOGGING_PROFILE_NAME
Note

If you are using Maven and the maven-war-plugin, put your MANIFEST.MF file in src/main/resources/META-INF/ and add the following configuration to your pom.xml file:

<plugin>
  <artifactId>maven-war-plugin</artifactId>
  <configuration>
    <archive>
      <manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>
    </archive>
  </configuration>
</plugin>

When the application is deployed, it will use the configuration in the specified logging profile for its log messages.

For an example of how to configure a logging profile and the application using it, see Example Logging Profile Configuration in the JBoss EAP Configuration Guide.

4.5. Internationalization and Localization

4.5.1. Introduction

4.5.1.1. About Internationalization

Internationalization is the process of designing software so that it can be adapted to different languages and regions without engineering changes.

4.5.1.2. About Localization

Localization is the process of adapting internationalized software for a specific region or language by adding locale-specific components and translations of text.

4.5.2. JBoss Logging Tools Internationalization and Localization

JBoss Logging Tools is a Java API that provides support for the internationalization and localization of log messages, exception messages, and generic strings. In addition to providing a mechanism for translation, JBoss Logging Tools also provides support for unique identifiers for each log message.

Internationalized messages and exceptions are created as method definitions inside of interfaces annotated using org.jboss.logging.annotations annotations. Implementing the interfaces is not necessary; JBoss Logging Tools does this at compile time. Once defined, you can use these methods to log messages or obtain exception objects in your code.

Internationalized logging and exception interfaces created with JBoss Logging Tools can be localized by creating a properties file for each bundle containing the translations for a specific language and region. JBoss Logging Tools can generate template property files for each bundle that can then be edited by a translator.

JBoss Logging Tools creates an implementation of each bundle for each corresponding translations property file in your project. All you have to do is use the methods defined in the bundles and JBoss Logging Tools ensures that the correct implementation is invoked for your current regional settings.

Message IDs and project codes are unique identifiers that are prepended to each log message. These unique identifiers can be used in documentation to make it easy to find information about log messages. With adequate documentation, the meaning of a log message can be determined from the identifiers regardless of the language that the message was written in.

The JBoss Logging Tools includes support for the following features:

MessageLogger
This interface in the org.jboss.logging.annotations package is used to define internationalized log messages. A message logger interface is annotated with @MessageLogger.
MessageBundle
This interface can be used to define generic translatable messages and Exception objects with internationalized messages. A message bundle is not used for creating log messages. A message bundle interface is annotated with @MessageBundle.
Internationalized Log Messages

These log messages are created by defining a method in a MessageLogger. The method must be annotated with the @LogMessage and @Message annotations and must specify the log message using the value attribute of @Message. Internationalized log messages are localized by providing translations in a properties file.

JBoss Logging Tools generates the required logging classes for each translation at compile time and invokes the correct methods for the current locale at runtime.

Internationalized Exceptions
An internationalized exception is an exception object returned from a method defined in a MessageBundle. These message bundles can be annotated to define a default exception message. The default message is replaced with a translation if one is found in a matching properties file for the current locale. Internationalized exceptions can also have project codes and message IDs assigned to them.
Internationalized Messages
An internationalized message is a string returned from a method defined in a MessageBundle. Message bundle methods that return Java String objects can be annotated to define the default content of that string, known as the message. The default message is replaced with a translation if one is found in a matching properties file for the current locale.
Translation Properties Files
Translation properties files are Java properties files that contain the translations of messages from one interface for one locale, country, and variant. Translation properties files are used by the JBoss Logging Tools to generate the classes that return the messages.
JBoss Logging Tools Project Codes

Project codes are strings of characters that identify groups of messages. They are displayed at the beginning of each log message, prepended to the message ID. Project codes are defined with the projectCode attribute of the @MessageLogger annotation.

Note

For a complete list of the new log message project code prefixes, see the Project Codes used in JBoss EAP 7.0.

JBoss Logging Tools Message IDs
Message IDs are numbers that uniquely identify a log message when combined with a project code. Message IDs are displayed at the beginning of each log message, appended to the project code for the message. Message IDs are defined with the ID attribute of the @Message annotation.

The logging-tools quickstart that ships with JBoss EAP is a simple Maven project that provides a working example of many of the features of JBoss Logging Tools. The code examples that follow are taken from the logging-tools quickstart.

4.5.3. Creating Internationalized Loggers, Messages and Exceptions

4.5.3.1. Create Internationalized Log Messages

You can use JBoss Logging Tools to create internationalized log messages by creating MessageLogger interfaces.

Note

This topic does not cover all optional features or the localization of the log messages.

  1. If you have not yet done so, configure your Maven settings to use the JBoss EAP Maven repository.

    For more information, see Configure the JBoss EAP Maven Repository Using the Maven Settings.

  2. Configure the project’s pom.xml file to use JBoss Logging Tools.

    For details, see JBoss Logging Tools Maven Configuration.

  3. Create a message logger interface by adding a Java interface to your project to contain the log message definitions.

    Name the interface to describe the log messages it will define. The log message interface has the following requirements:

    • It must be annotated with @org.jboss.logging.annotations.MessageLogger.
    • Optionally, it can extend org.jboss.logging.BasicLogger.
    • The interface must define a field that is a message logger of the same type as the interface. Do this with the getMessageLogger() method of @org.jboss.logging.Logger.

      Logger Interface Code Example

      package com.company.accounts.loggers;
      
      import org.jboss.logging.BasicLogger;
      import org.jboss.logging.Logger;
      import org.jboss.logging.annotations.MessageLogger;
      
      @MessageLogger(projectCode="")
      interface AccountsLogger extends BasicLogger {
         AccountsLogger LOGGER = Logger.getMessageLogger(
               AccountsLogger.class,
               AccountsLogger.class.getPackage().getName() );
      }

  4. Add a method definition to the interface for each log message.

    Name each method descriptively for the log message that it represents. Each method has the following requirements:

    • The method must return void.
    • It must be annotated with the @org.jboss.logging.annotation.LogMessage annotation.
    • It must be annotated with the @org.jboss.logging.annotations.Message annotation.
    • The default log level is INFO.
    • The value attribute of @org.jboss.logging.annotations.Message contains the default log message, which is used if no translation is available.

      @LogMessage
      @Message(value = "Customer query failed, Database not available.")
      void customerQueryFailDBClosed();
  5. Invoke the methods by adding the calls to the interface methods in your code where the messages must be logged from.

    Creating implementations of the interfaces is not necessary, the annotation processor does this for you when the project is compiled.

    AccountsLogger.LOGGER.customerQueryFailDBClosed();

    The custom loggers are subclassed from BasicLogger, so the logging methods of BasicLogger can also be used. It is not necessary to create other loggers to log non-internationalized messages.

    AccountsLogger.LOGGER.error("Invalid query syntax.");
  6. The project now supports one or more internationalized loggers that can be localized.
Note

The logging-tools quickstart that ships with JBoss EAP is a simple Maven project that provides a working example of how to use JBoss Logging Tools.

4.5.3.2. Create and Use Internationalized Messages

This procedure demonstrates how to create and use internationalized messages.

Note

This section does not cover all optional features or the process of localizing those messages.

  1. If you have not yet done so, configure your Maven settings to use the JBoss EAP Maven repository. For more information, see Configure the JBoss EAP Maven Repository Using the Maven Settings.
  2. Configure the project’s pom.xml file to use JBoss Logging Tools. For details, see JBoss Logging Tools Maven Configuration.
  3. Create an interface for the exceptions. JBoss Logging Tools defines internationalized messages in interfaces. Name each interface descriptively for the messages that it contains. The interface has the following requirements:

    • It must be declared as public.
    • It must be annotated with @org.jboss.logging.annotations.MessageBundle.
    • The interface must define a field that is a message bundle of the same type as the interface.

      Interface Code Example

      @MessageBundle(projectCode="")
      public interface GreetingMessageBundle {
         GreetingMessageBundle MESSAGES = Messages.getBundle(GreetingMessageBundle.class);
      }

      Note

      Calling Messages.getBundle(GreetingMessagesBundle.class) is equivalent to calling Messages.getBundle(GreetingMessagesBundle.class, Locale.getDefault()).

      Locale.getDefault() gets the current value of the default locale for this instance of the Java Virtual Machine. The Java Virtual Machine sets the default locale during startup, based on the host environment. It is used by many locale-sensitive methods if no locale is explicitly specified. It can be changed using the setDefault method.

      See Set the Default Locale of the Server in the JBoss EAP Configuration Guide for more information.

  4. Add a method definition to the interface for each message. Name each method descriptively for the message that it represents. Each method has the following requirements:

    • It must return an object of type String.
    • It must be annotated with the @org.jboss.logging.annotations.Message annotation.
    • The value attribute of @org.jboss.logging.annotations.Message must be set to the default message. This is the message that is used if no translation is available.

      Method Definition Code Example

      @Message(value = "Hello world.")
      String helloworldString();

  5. Invoke the interface methods in your application where you need to obtain the message:

    Method Invocation Code Example

    System.out.println(helloworldString());

The project now supports internationalized message strings that can be localized.

Note

See the logging-tools quickstart that ships with JBoss EAP for a complete working example.

4.5.3.3. Create Internationalized Exceptions

You can use JBoss Logging Tools to create and use internationalized exceptions.

The following instructions assume that you want to add internationalized exceptions to an existing software project that is built using either Red Hat JBoss Developer Studio or Maven.

Note

This topic does not cover all optional features or the process of localization of those exceptions.

  1. Configure the project’s pom.xml file to use JBoss Logging Tools. For details, see JBoss Logging Tools Maven Configuration.
  2. Create an interface for the exceptions. JBoss Logging Tools defines internationalized exceptions in interfaces. Name each interface descriptively for the exceptions that will be defined in it. The interface has the following requirements:

    • It must be declared as public.
    • It must be annotated with @MessageBundle.
    • The interface must define a field that is a message bundle of the same type as the interface.

      @MessageBundle(projectCode="")
      public interface ExceptionBundle {
         ExceptionBundle EXCEPTIONS = Messages.getBundle(ExceptionBundle.class);
      }
  3. Add a method definition to the interface for each exception. Name each method descriptively for the exception that it represents. Each method has the following requirements:

    • It must return an Exception object, or a sub-type of Exception.
    • It must be annotated with the @org.jboss.logging.annotations.Message annotation.
    • The value attribute of @org.jboss.logging.annotations.Message must be set to the default exception message. This is the message that is used if no translation is available.
    • If the exception being returned has a constructor that requires parameters in addition to a message string, then those parameters must be supplied in the method definition using the @Param annotation. The parameters must be the same type and order as they are in the constructor of the exception.

      @Message(value = "The config file could not be opened.")
      IOException configFileAccessError();
      
      @Message(id = 13230, value = "Date string '%s' was invalid.")
      ParseException dateWasInvalid(String dateString, @Param int errorOffset);
  4. Invoke the interface methods in your code where you need to obtain one of the exceptions. The methods do not throw the exceptions, they return the exception object, which you can then throw.

    try {
       propsInFile=new File(configname);
       props.load(new FileInputStream(propsInFile));
    }
    catch(IOException ioex) {
      //in case props file does not exist
       throw ExceptionBundle.EXCEPTIONS.configFileAccessError();
    }

The project now supports internationalized exceptions that can be localized.

Note

See the logging-tools quickstart that ships with JBoss EAP for a complete working example.

4.5.4. Localizing Internationalized Loggers, Messages and Exceptions

4.5.4.1. Generate New Translation Properties Files with Maven

Projects that are built using Maven can generate empty translation property files for each MessageLogger and MessageBundle it contains. These files can then be used as new translation property files.

The following procedure demonstrates how to configure a Maven project to generate new translation property files.

Prerequisites

  • You must already have a working Maven project.
  • The project must already be configured for JBoss Logging Tools.
  • The project must contain one or more interfaces that define internationalized log messages or exceptions.

Generate the Translation Properties Files

  1. Add the Maven configuration by adding the -AgenereatedTranslationFilePath compiler argument to the Maven compiler plug-in configuration, and assign it the path where the new files will be created.

    This configuration creates the new files in the target/generated-translation-files directory of your Maven project.

    <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-compiler-plugin</artifactId>
       <version>2.3.2</version>
       <configuration>
          <source>1.6</source>
          <target>1.6</target>
          <compilerArgument>
          -AgeneratedTranslationFilesPath=${project.basedir}/target/generated-translation-files
          </compilerArgument>
          <showDeprecation>true</showDeprecation>
       </configuration>
    </plugin>
  2. Build the project using Maven:

    $ mvn compile

    One properties file is created for each interface annotated with @MessageBundle or @MessageLogger.

    • The new files are created in a subdirectory corresponding to the Java package in which each interface is declared.
    • Each new file is named using the following pattern where INTERFACE_NAME is the name of the interface used to generated the file.

      INTERFACE_NAME.i18n_locale_COUNTRY_VARIANT.properties

The resulting files can now be copied into your project as the basis for new translations.

Note

See the logging-tools quickstart that ships with JBoss EAP for a complete working example.

4.5.4.2. Translate an Internationalized Logger, Exception, or Message

Properties files can be used to provide translations for logging and exception messages defined in interfaces using JBoss Logging Tools.

The following procedure shows how to create and use a translation properties file, and assumes that you already have a project with one or more interfaces defined for internationalized exceptions or log messages.

Prerequisites

  • You must already have a working Maven project.
  • The project must already be configured for JBoss Logging Tools.
  • The project must contain one or more interfaces that define internationalized log messages or exceptions.
  • The project must be configured to generate template translation property files.

Translate an Internationalized Logger, Exception, or Message

  1. Run the following command to create the template translation properties files:

    $ mvn compile
  2. Copy the template for the interfaces that you want to translate from the directory where they were created into the src/main/resources directory of your project. The properties files must be in the same package as the interfaces they are translating.
  3. Rename the copied template file to indicate the language it will contain. For example: GreeterLogger.i18n_fr_FR.properties.
  4. Edit the contents of the new translation properties file to contain the appropriate translation:

    # Level: Logger.Level.INFO
    # Message: Hello message sent.
    logHelloMessageSent=Bonjour message envoyé.
  5. Repeat the process of copying the template and modifying it for each translation in the bundle.

The project now contains translations for one or more message or logger bundles. Building the project generates the appropriate classes to log messages with the supplied translations. It is not necessary to explicitly invoke methods or supply parameters for specific languages, JBoss Logging Tools automatically uses the correct class for the current locale of the application server.

The source code of the generated classes can be viewed under target/generated-sources/annotations/.

4.5.5. Customizing Internationalized Log Messages

4.5.5.1. Add Message IDs and Project Codes to Log Messages

This procedure demonstrates how to add message IDs and project codes to internationalized log messages created using JBoss Logging Tools. A log message must have both a project code and message ID to be displayed in the log. If a message does not have both a project code and a message ID, then neither is displayed.

Prerequisites

  1. You must already have a project with internationalized log messages. For details, see Create Internationalized Log Messages.
  2. You need to know the project code you will be using. You can use a single project code, or define different ones for each interface.

Add Message IDs and Project Codes to Log Messages

  1. Specify the project code for the interface by using the projectCode attribute of the @MessageLogger annotation attached to a custom logger interface. All messages that are defined in the interface will use that project code.

    @MessageLogger(projectCode="ACCNTS")
    interface AccountsLogger extends BasicLogger {
    
    }
  2. Specify a message ID for each message using the id attribute of the @Message annotation attached to the method that defines the message.

    @LogMessage
    @Message(id=43, value = "Customer query failed, Database not available.")  void customerQueryFailDBClosed();
  3. The log messages that have both a message ID and project code associated with them will prepend these to the logged message.

    10:55:50,638 INFO  [com.company.accounts.ejb] (MSC service thread 1-4) ACCNTS000043: Customer query failed, Database not available.

4.5.5.2. Specify the Log Level for a Message

The default log level of a message defined by an interface by JBoss Logging Tools is INFO. A different log level can be specified with the level attribute of the @LogMessage annotation attached to the logging method. Use the following procedure to specify a different log level.

  1. Add the level attribute to the @LogMessage annotation of the log message method definition.
  2. Assign the log level for this message using the level attribute. The valid values for level are the six enumerated constants defined in org.jboss.logging.Logger.Level: DEBUG, ERROR, FATAL, INFO, TRACE, and WARN.

    import org.jboss.logging.Logger.Level;
    
    @LogMessage(level=Level.ERROR)
    @Message(value = "Customer query failed, Database not available.")
    void customerQueryFailDBClosed();

Invoking the logging method in the above sample will produce a log message at the level of ERROR.

10:55:50,638 ERROR  [com.company.app.Main] (MSC service thread 1-4)
 Customer query failed, Database not available.

4.5.5.3. Customize Log Messages with Parameters

Custom logging methods can define parameters. These parameters are used to pass additional information to be displayed in the log message. Where the parameters appear in the log message is specified in the message itself using either explicit or ordinary indexing.

Customize Log Messages with Parameters

  1. Add parameters of any type to the method definition. Regardless of type, the String representation of the parameter is what is displayed in the message.
  2. Add parameter references to the log message. References can use explicit or ordinary indexes.

    • To use ordinary indexes, insert %s characters in the message string where you want each parameter to appear. The first instance of %s will insert the first parameter, the second instance will insert the second parameter, and so on.
    • To use explicit indexes, insert %#$s characters in the message, where # indicates the number of the parameter that you wish to appear.

Using explicit indexes allows the parameter references in the message to be in a different order than they are defined in the method. This is important for translated messages that may require different ordering of parameters.

Important

The number of parameters must match the number of references to the parameters in the specified message or the code will not compile. A parameter marked with the @Cause annotation is not included in the number of parameters.

The following is an example of message parameters using ordinary indexes:

@LogMessage(level=Logger.Level.DEBUG)
@Message(id=2, value="Customer query failed, customerid:%s, user:%s")
void customerLookupFailed(Long customerid, String username);

The following is an example of message parameters using explicit indexes:

@LogMessage(level=Logger.Level.DEBUG)
@Message(id=2, value="Customer query failed, user:%2$s, customerid:%1$s")
void customerLookupFailed(Long customerid, String username);

4.5.5.4. Specify an Exception as the Cause of a Log Message

JBoss Logging Tools allows one parameter of a custom logging method to be defined as the cause of the message. This parameter must be the Throwable type or any of its sub-classes, and is marked with the @Cause annotation. This parameter cannot be referenced in the log message like other parameters, and is displayed after the log message.

The following procedure shows how to update a logging method using the @Cause parameter to indicate the "causing" exception. It is assumed that you have already created internationalized logging messages to which you want to add this functionality.

Specify an Exception as the Cause of a Log Message

  1. Add a parameter of the type Throwable or its subclass to the method.

    @LogMessage
    @Message(id=404, value="Loading configuration failed. Config file:%s")
    void loadConfigFailed(Exception ex, File file);
  2. Add the @Cause annotation to the parameter.

    import org.jboss.logging.annotations.Cause
    
    @LogMessage
    @Message(value = "Loading configuration failed. Config file: %s")
    void loadConfigFailed(@Cause Exception ex, File file);
  3. Invoke the method. When the method is invoked in your code, an object of the correct type must be passed and will be displayed after the log message.

    try
    {
       confFile=new File(filename);
       props.load(new FileInputStream(confFile));
    }
    catch(Exception ex) //in case properties file cannot be read
    {
         ConfigLogger.LOGGER.loadConfigFailed(ex, filename);
    }

The following is the output of the above code samples if the code threw an exception of type FileNotFoundException:

10:50:14,675 INFO [com.company.app.Main] (MSC service thread 1-3) Loading configuration failed. Config file: customised.properties
java.io.FileNotFoundException: customised.properties (No such file or directory)
   at java.io.FileInputStream.open(Native Method)
   at java.io.FileInputStream.<init>(FileInputStream.java:120)
   at com.company.app.demo.Main.openCustomProperties(Main.java:70)
   at com.company.app.Main.go(Main.java:53)
   at com.company.app.Main.main(Main.java:43)

4.5.6. Customizing Internationalized Exceptions

4.5.6.1. Add Message IDs and Project Codes to Exception Messages

Message IDs and project codes are unique identifiers that are prepended to each message displayed by internationalized exceptions. These identifying codes make it possible to create a reference for all the exception messages in an application. This allows someone to look up the meaning of an exception message written in language that they do not understand.

The following procedure demonstrates how to add message IDs and project codes to internationalized exception messages created using JBoss Logging Tools.

Prerequisites

  1. You must already have a project with internationalized exceptions. For details, see Create Internationalized Exceptions.
  2. You need to know the project code you will be using. You can use a single project code, or define different ones for each interface.

Add Message IDs and Project Codes to Exception Messages

  1. Specify the project code using the projectCode attribute of the @MessageBundle annotation attached to a exception bundle interface. All messages that are defined in the interface will use that project code.

    @MessageBundle(projectCode="ACCTS")
    interface ExceptionBundle
    {
       ExceptionBundle EXCEPTIONS = Messages.getBundle(ExceptionBundle.class);
    }
  2. Specify message IDs for each exception using the id attribute of the @Message annotation attached to the method that defines the exception.

    @Message(id=143, value = "The config file could not be opened.")
    IOException configFileAccessError();
Important

A message that has both a project code and message ID displays them prepended to the message. If a message does not have both a project code and a message ID, neither is displayed.

Internationalized Exception Example

This exception bundle interface example uses the project code of "ACCTS". It contains a single exception method with the ID of "143".

@MessageBundle(projectCode="ACCTS")
interface ExceptionBundle
{
    ExceptionBundle EXCEPTIONS = Messages.getBundle(ExceptionBundle.class);

    @Message(id=143, value = "The config file could not be opened.")
    IOException configFileAccessError();
}

The exception object can be obtained and thrown using the following code:

throw ExceptionBundle.EXCEPTIONS.configFileAccessError();

This would display an exception message like the following:

Exception in thread "main" java.io.IOException: ACCTS000143: The config file could not be opened.
at com.company.accounts.Main.openCustomProperties(Main.java:78)
at com.company.accounts.Main.go(Main.java:53)
at com.company.accounts.Main.main(Main.java:43)

4.5.6.2. Customize Exception Messages with Parameters

Exception bundle methods that define exceptions can specify parameters to pass additional information to be displayed in the exception message. The exact position of the parameters in the exception message is specified in the message itself using either explicit or ordinary indexing.

Customize Exception Messages with Parameters

  1. Add parameters of any type to the method definition. Regardless of type, the String representation of the parameter is what is displayed in the message.
  2. Add parameter references to the exception message. References can use explicit or ordinary indexes.

    • To use ordinary indexes, insert %s characters in the message string where you want each parameter to appear. The first instance of %s will insert the first parameter, the second instance will insert the second parameter, and so on.
    • To use explicit indexes, insert %#$s characters in the message, where # indicates the number of the parameter that you wish to appear.

Using explicit indexes allows the parameter references in the message to be in a different order than they are defined in the method. This is important for translated messages that may require different ordering of parameters.

Important

The number of parameters must match the number of references to the parameters in the specified message, or the code will not compile. A parameter marked with the @Cause annotation is not included in the number of parameters.

The following is an example of message parameters using ordinary indexes:

@Message(id=2, value="Customer query failed, customerid:%s, user:%s")
void customerLookupFailed(Long customerid, String username);

The following is an example of message parameters using explicit indexes:

@Message(id=2, value="Customer query failed, user:%2$s, customerid:%1$s")
void customerLookupFailed(Long customerid, String username);

4.5.6.3. Specify One Exception as the Cause of Another Exception

Exceptions returned by exception bundle methods can have another exception specified as the underlying cause. This is done by adding a parameter to the method and annotating the parameter with @Cause. This parameter is used to pass the causing exception, and cannot be referenced in the exception message.

The following procedure shows how to update a method from an exception bundle using the @Cause parameter to indicate the causing exception. It is assumed that you have already created an exception bundle to which you want to add this functionality.

  1. Add a parameter of the type Throwable or its subclass to the method.

    @Message(id=328, value = "Error calculating: %s.")
    ArithmeticException calculationError(Throwable cause, String msg);
  2. Add the @Cause annotation to the parameter.

    import org.jboss.logging.annotations.Cause
    
    @Message(id=328, value = "Error calculating: %s.")
    ArithmeticException calculationError(@Cause Throwable cause, String msg);
  3. Invoke the interface method to obtain an exception object. The most common use case is to throw a new exception from a catch block using the caught exception as the cause.

    try
    {
       ...
    }
    catch(Exception ex)
    {
       throw ExceptionBundle.EXCEPTIONS.calculationError(
                                        ex, "calculating payment due per day");
    }

The following is an example of specifying an exception as the cause of another exception. This exception bundle defines a single method that returns an exception of type ArithmeticException.

@MessageBundle(projectCode = "TPS")
interface CalcExceptionBundle
{
    CalcExceptionBundle EXCEPTIONS = Messages.getBundle(CalcExceptionBundle.class);

    @Message(id=328, value = "Error calculating: %s.")
    ArithmeticException calcError(@Cause Throwable cause, String value);
}

This code snippet performs an operation that throws an exception, because it attempts to divide an integer by zero. The exception is caught, and a new exception is created using the first one as the cause.

int totalDue = 5;
int daysToPay = 0;
int amountPerDay;

try
{
   amountPerDay = totalDue/daysToPay;
}
catch (Exception ex)
{
   throw CalcExceptionBundle.EXCEPTIONS.calcError(ex, "payments per day");
}

The following is an example of the exception message:

Exception in thread "main" java.lang.ArithmeticException: TPS000328: Error calculating: payments per day.
    at com.company.accounts.Main.go(Main.java:58)
    at com.company.accounts.Main.main(Main.java:43)
Caused by: java.lang.ArithmeticException: / by zero
    at com.company.accounts.Main.go(Main.java:54)
    ... 1 more

4.5.7. References

4.5.7.1. JBoss Logging Tools Maven Configuration

The following procedure configures a Maven project to use JBoss Logging and JBoss Logging Tools for internationalization.

  1. If you have not yet done so, configure your Maven settings to use the JBoss EAP repository. For more information, see Configure the JBoss EAP Maven Repository Using the Maven Settings.

    Include the jboss-eap-javaee7 BOM in the <dependencyManagement> section of the project’s pom.xml file.

    <dependencyManagement>
      <dependencies>
        <!-- JBoss distributes a complete set of Java EE APIs including
          a Bill of Materials (BOM). A BOM specifies the versions of a "stack" (or
          a collection) of artifacts. We use this here so that we always get the correct versions of artifacts.
          Here we use the jboss-javaee-7.0 stack (you can
          read this as the JBoss stack of the Java EE APIs). You can actually
          use this stack with any version of JBoss EAP that implements Java EE. -->
        <dependency>
          <groupId>org.jboss.bom</groupId>
           <artifactId>jboss-eap-javaee7</artifactId>
           <version>${version.jboss.bom.eap}</version>
           <type>pom</type>
           <scope>import</scope>
        </dependency>
      <dependencies>
    <dependencyManagement>
  2. Add the Maven dependencies to the project’s pom.xml file:

    1. Add the jboss-logging dependency for access to JBoss Logging framework.
    2. If you plan to use the JBoss Logging Tools, also add the jboss-logging-processor dependency.

      Both of these dependencies are available in JBoss EAP BOM that was added in the previous step, so the scope element of each can be set to provided as shown.

      <!-- Add the JBoss Logging Tools dependencies -->
      <!-- The jboss-logging API -->
      <dependency>
         <groupId>org.jboss.logging</groupId>
         <artifactId>jboss-logging</artifactId>
         <scope>provided</scope>
      </dependency>
      <!-- Add the jboss-logging-tools processor if you are using JBoss Tools  -->
      <dependency>
         <groupId>org.jboss.logging</groupId>
         <artifactId>jboss-logging-processor</artifactId>
         <scope>provided</scope>
      </dependency>
  3. The maven-compiler-plugin must be at least version 3.1 and configured for target and generated sources of 1.8.

    <plugin>
       <groupId>org.apache.maven.plugins</groupId>
       <artifactId>maven-compiler-plugin</artifactId>
       <version>3.1</version>
       <configuration>
          <source>1.8</source>
          <target>1.8</target>
       </configuration>
    </plugin>
Note

For a complete working example of a pom.xml file that is configured to use JBoss Logging Tools, see the logging-tools quickstart that ships with JBoss EAP.

4.5.7.2. Translation Property File Format

The property files used for the translation of messages in JBoss Logging Tools are standard Java property files. The format of the file is the simple line-oriented, key=value pair format described in the java.util.Properties class documentation.

The file name format has the following format:

InterfaceName.i18n_locale_COUNTRY_VARIANT.properties
  • InterfaceName is the name of the interface that the translations apply to.
  • locale, COUNTRY, and VARIANT identify the regional settings that the translation applies to.
  • locale and COUNTRY specify the language and country using the ISO-639 and ISO-3166 Language and Country codes respectively. COUNTRY is optional.
  • VARIANT is an optional identifier that can be used to identify translations that only apply to a specific operating system or browser.

The properties contained in the translation file are the names of the methods from the interface being translated. The assigned value of the property is the translation. If a method is overloaded, then this is indicated by appending a dot and then the number of parameters to the name. Methods for translation can only be overloaded by supplying a different number of parameters.

Translation Properties File Example

File name: GreeterService.i18n_fr_FR_POSIX.properties.

# Level: Logger.Level.INFO
# Message: Hello message sent.
logHelloMessageSent=Bonjour message envoyé.

4.5.7.3. JBoss Logging Tools Annotations Reference

The following annotations are defined in JBoss Logging for use with internationalization and localization of log messages, strings, and exceptions.

Table 4.1. JBoss Logging Tools Annotations

AnnotationTargetDescriptionAttributes

@MessageBundle

Interface

Defines the interface as a message bundle.

projectCode

@MessageLogger

Interface

Defines the interface as a message logger.

projectCode

@Message

Method

Can be used in message bundles and message loggers. In a message bundle it defines the method as being one that returns a localized String or Exception object. In a message logger it defines a method as being a localized logger.

value, id

@LogMessage

Method

Defines a method in a message logger as being a logging method.

level (default INFO)

@Cause

Parameter

Defines a parameter as being one that passes an Exception as the cause of either a Log message or another Exception.

-

@Param

Parameter

Defines a parameter as being one that is passed to the constructor of the Exception.

-

4.5.7.4. Project Codes Used in JBoss EAP

The following table lists all the project codes used in JBoss EAP 7.0, along with the Maven modules they belong to.

Table 4.2. Project Codes Used in JBoss EAP

Maven ModuleProject Code

appclient

WFLYAC

batch/extension-jberet

WFLYBATCH

batch/extension

WFLYBATCH-DEPRECATED

batch/jberet

WFLYBAT

bean-validation

WFLYBV

controller-client

WFLYCC

controller

WFLYCTL

clustering/common

WFLYCLCOM

clustering/ejb/infinispan

WFLYCLEJBINF

clustering/infinispan/extension

WFLYCLINF

clustering/jgroups/extension

WFLYCLJG

clustering/server

WFLYCLSV

clustering/web/infinispan

WFLYCLWEBINF

connector

WFLYJCA

deployment-repository

WFLYDR

deployment-scanner

WFLYDS

domain-http

WFLYDMHTTP

domain-management

WFLYDM

ee

WFLYEE

ejb3

WFLYEJB

embedded

WFLYEMB

host-controller

WFLYDC

host-controller

WFLYHC

iiop-openjdk

WFLYIIOP

io/subsystem

WFLYIO

jaxrs

WFLYRS

jdr

WFLYJDR

jmx

WFLYJMX

jpa/hibernate5

JIPI

jpa/spi/src/main/java/org/jipijapa/JipiLogger.java

JIPI

jpa/subsystem

WFLYJPA

jsf/subsystem

WFLYJSF

jsr77

WFLYEEMGMT

launcher

WFLYLNCHR

legacy

WFLYORB

legacy

WFLYMSG

legacy

WFLYWEB

logging

WFLYLOG

mail

WFLYMAIL

management-client-content

WFLYCNT

messaging-activemq

WFLYMSGAMQ

mod_cluster/extension

WFLYMODCLS

naming

WFLYNAM

network

WFLYNET

patching

WFLYPAT

picketlink

WFLYPL

platform-mbean

WFLYPMB

pojo

WFLYPOJO

process-controller

WFLYPC

protocol

WFLYPRT

remoting

WFLYRMT

request-controller

WFLYREQCON

rts

WFLYRTS

sar

WFLYSAR

security-manager

WFLYSM

security

WFLYSEC

server

WFLYSRV

system-jmx

WFLYSYSJMX

threads

WFLYTHR

transactions

WFLYTX

undertow

WFLYUT

webservices/server-integration

WFLYWS

weld

WFLYWELD

xts

WFLYXTS

Chapter 5. Remote JNDI lookup

5.1. Registering objects to JNDI

The Java Naming and Directory Interface (JNDI) is a Java API for a directory service that allows Java software clients to discover and look up objects via a name.

If an object, registered to JNDI, is supposed to be looked up by remote JNDI clients (i.e. a client that runs in a separate JVM), then it must be registered under java:jboss/exported context.

For example, if the JMS queue in a messaging-activemq subsystem must be exposed for remote JNDI clients, then it must be registred to JNDI, like java:jboss/exported/jms/queue/myTestQueue. Remote JNDI client can look it up by name jms/queue/myTestQueue.

Example: Configuration of the queue in standalone-full(-ha).xml

<subsystem xmlns="urn:jboss:domain:messaging-activemq:1.0">
  <server name="default">
    ...
    <jms-queue name="myTestQueue" entries="java:jboss/exported/jms/queue/myTestQueue"/>
    ...
  </server>
</subsystem>

5.2. Configuring remote JNDI

A remote JNDI client can connect and lookup objects by name from JNDI. It must have jboss-client.jar on its class path. The jboss-client.jar is available at EAP_HOME/bin/client/jboss-client.jar.

The following example shows how to lookup the myTestQueue queue from JNDI in remote JNDI client:

Example: Configuration for an MDB Resource Adapter

Properties properties = new Properties();
properties.put(Context.INITIAL_CONTEXT_FACTORY, "org.jboss.naming.remote.client.InitialContextFactory");
properties.put(Context.PROVIDER_URL, "http-remoting://<hostname>:8080");
context = new InitialContext(properties);
Queue myTestQueue = (Queue) context.lookup("jms/queue/myTestQueue");

Chapter 6. Clustering in Web Applications

6.1. Session Replication

6.1.1. About HTTP Session Replication

Session replication ensures that client sessions of distributable applications are not disrupted by failovers of nodes in a cluster. Each node in the cluster shares information about ongoing sessions, and can take over sessions if a node disappears.

Session replication is the mechanism by which mod_cluster, mod_jk, mod_proxy, ISAPI, and NSAPI clusters provide high availability.

6.1.2. Enable Session Replication in Your Application

To take advantage of JBoss EAP High Availability (HA) features and enable clustering of your web application, you must configure your application to be distributable.

Make your Application Distributable
  1. Indicate that your application is distributable. If your application is not marked as distributable, its sessions will never be distributed. Add the <distributable/> element inside the <web-app> tag of your application’s web.xml descriptor file:

    Example: Minimum Configuration for a Distributable Application

    <?xml version="1.0"?>
    <web-app  xmlns="http://java.sun.com/xml/ns/j2ee"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
                                  http://java.sun.com/xml/ns/j2ee/web-app_3_0.xsd"
              version="3.0">
    
          <distributable/>
    
    </web-app>

  2. Next, if desired, modify the default replication behavior. If you want to change any of the values affecting session replication, you can override them inside a <replication-config> element inside <jboss-web> in an application’s WEB-INF/jboss-web.xml file. For a given element, only include it if you want to override the defaults.

    Example: <replication-config> Values

    <jboss-web xmlns="http://www.jboss.com/xml/ns/javaee"
               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss-web_10_0.xsd">
       <replication-config>
          <replication-granularity>SESSION</replication-granularity>
        </replication-config>
    </jboss-web>

The <replication-granularity> parameter determines the granularity of data that is replicated. It defaults to SESSION, but can be set to ATTRIBUTE to increase performance on sessions where most attributes remain unchanged.

Valid values for <replication-granularity> can be :

  • SESSION: The default value. The entire session object is replicated if any attribute is dirty. This policy is required if an object reference is shared by multiple session attributes. The shared object references are maintained on remote nodes since the entire session is serialized in one unit.
  • ATTRIBUTE: This is only for dirty attributes in the session and for some session data, such as the last-accessed timestamp.
Immutable Session Attributes

For JBoss EAP7, session replication is triggered when the session is mutated or when any mutable attribute of the session is accessed. Session attributes are assumed to be mutable unless one of the following is true:

  • The value is a known immutable value:

    • null
    • java.util.Collections.EMPTY_LIST, EMPTY_MAP, EMPTY_SET
  • The value type is or implements a known immutable type:

    • java.lang.Boolean, Character, Byte, Short, Integer, Long, Float, Double
    • java.lang.Class, Enum, StackTraceElement, String
    • java.io.File, java.nio.file.Path
    • java.math.BigDecimal, BigInteger, MathContext
    • java.net.Inet4Address, Inet6Address, InetSocketAddress, URI, URL
    • java.security.Permission
    • java.util.Currency, Locale, TimeZone, UUID
    • java.time.Clock, Duration, Instant, LocalDate, LocalDateTime, LocalTime, MonthDay, Period, Year, YearMonth, ZoneId, ZoneOffset, ZonedDateTime
    • java.time.chrono.ChronoLocalDate, Chronology, Era
    • java.time.format.DateTimeFormatter, DecimalStyle
    • java.time.temporal.TemporalField, TemporalUnit, ValueRange, WeekFields
    • java.time.zone.ZoneOffsetTransition, ZoneOffsetTransitionRule, ZoneRules
  • The value type is annotated with:

    • @org.wildfly.clustering.web.annotation.Immutable
    • @net.jcip.annotations.Immutable

6.2. HTTP Session Passivation and Activation

6.2.1. About HTTP Session Passivation and Activation

Passivation is the process of controlling memory usage by removing relatively unused sessions from memory while storing them in persistent storage.

Activation is when passivated data is retrieved from persisted storage and put back into memory.

Passivation occurs at different times in an HTTP session’s lifetime:

  • When the container requests the creation of a new session, if the number of currently active sessions exceeds a configurable limit, the server attempts to passivate some sessions to make room for the new one.
  • When a web application is deployed and a backup copy of sessions active on other servers is acquired by the newly deploying web application’s session manager, sessions may be passivated.

A session is passivated if the number of active sessions exceeds a configurable maximum.

Sessions are always passivated using a Least Recently Used (LRU) algorithm.

6.2.2. Configure HTTP Session Passivation in Your Application

HTTP session passivation is configured in your application’s WEB-INF/jboss-web.xml and META-INF/jboss-web.xml file.

Example: jboss-web.xml File

<jboss-web xmlns="http://www.jboss.com/xml/ns/javaee"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee http://www.jboss.org/j2ee/schema/jboss-web_10_0.xsd">

   <max-active-sessions>20</max-active-sessions>
</jboss-web>

The <max-active-sessions> element dictates the maximum number of active sessions allowed, and is used to enable session passivation. If session creation would cause the number of active sessions to exceed <max-active-sessions/>, then the oldest session known to the session manager will passivate to make room for the new session.

Note

The total number of sessions in memory includes sessions replicated from other cluster nodes that are not being accessed on this node. Take this into account when setting <max-active-sessions>. The number of sessions replicated from other nodes also depends on whether REPL or DIST cache mode is enabled. In REPL cache mode, each session is replicated to each node. In DIST cache mode, each session is replicated only to the number of nodes specified by the owners parameter. See Configure the Cache Mode in the JBoss EAP Config Guide for information on configuring session cache modes. For example, consider an eight node cluster, where each node handles requests from 100 users. With REPL cache mode, each node would store 800 sessions in memory. With DIST cache mode enabled, and the default owners setting of 2, each node stores 200 sessions in memory.

6.3. Public API for Clustering Services

JBoss EAP 7 introduces a refined public clustering API for use by applications. The new services are designed to be lightweight, easily injectable, with no external dependencies.

org.wildfly.clustering.group.Group

The group service provides a mechanism to view the cluster topology for a JGroups channel, and to be notified when the topology changes.

@Resource(lookup = "java:jboss/clustering/group/channel-name")
private Group channelGroup;
org.wildfly.clustering.dispatcher.CommandDispatcher

The CommandDispatcherFactory service provides a mechanism to create a dispatcher for executing commands on nodes in the cluster. The resulting CommandDispatcher is a command-pattern analog to the reflection-based GroupRpcDispatcher from previous JBoss EAP releases.

@Resource(lookup = "java:jboss/clustering/dispatcher/channel-name")
private CommandDispatcherFactory factory;

public void foo() {
    String context = "Hello world!";
    try (CommandDispatcher<String> dispatcher = this.factory.createCommandDispatcher(context)) {
        dispatcher.executeOnCluster(new StdOutCommand());
    }
}

public static class StdOutCommand implements Command<Void, String> {
    @Override
    public Void execute(String context) {
        System.out.println(context);
        return null;
    }
}

6.4. HA Singleton Service

A clustered singleton service, also known as a high-availability (HA) singleton, is a service deployed on multiple nodes in a cluster. The service is provided on only one of the nodes. The node running the singleton service is usually called the master node.

When the master node either fails or shuts down, another master is selected from the remaining nodes and the service is restarted on the new master. Other than a brief interval when one master has stopped and another has yet to take over, the service is provided by one, but only one, node.

HA Singleton ServiceBuilder API

JBoss EAP 7 introduces a new public API for building singleton services that simplifies the process significantly.

The SingletonServiceBuilder implementation installs its services so they will start asynchronously, preventing deadlocking of the Modular Service Container (MSC).

HA Singleton Service Election Policies

If there is a preference for which node should start the ha-singleton, you can set the election policy in the ServiceActivator class.

JBoss EAP provides two election policies:

  1. Simple Election Policy

    The simple election policy selects a master node based on the relative age. The required age is configured in the position property, which is the index in the list of available nodes where,

    • position = 0 – refers to the oldest node (the default)
    • position = 1 – refers to the 2nd oldest etc.

      Position can also be negative to indicate the youngest nodes.

    • position = -1 – refers to the youngest node
    • position = -2 – refers to the 2nd youngest node etc.
  2. Random Election Policy

    The random election policy elects a random member to be the provider of a singleton service.

Create an HA Singleton Service Application

The following is an abbreviated example of the steps required to create and deploy an application as a cluster-wide singleton service. This example service activates a scheduled timer that is started only once in the cluster.

  1. Create an HATimerService service that implements the org.jboss.msc.service.Service interface and contains the getValue(), start(), and stop() methods.

    Service Class Code Example

    public class HATimerService implements Service<String> {
        private static final Logger LOGGER = Logger.getLogger(HATimerService.class.toString());
        public static final ServiceName SINGLETON_SERVICE_NAME = ServiceName.JBOSS.append("quickstart", "ha", "singleton", "timer");
    
        /**
         * A flag whether the service is started.
         */
        private final AtomicBoolean started = new AtomicBoolean(false);
    
        /**
         * @return the name of the server node
         */
        public String getValue() throws IllegalStateException, IllegalArgumentException {
            LOGGER.info(String.format("%s is %s at %s", HATimerService.class.getSimpleName(), (started.get() ? "started" : "not started"), System.getProperty("jboss.node.name")));
            return System.getProperty("jboss.node.name");
        }
    
        public void start(StartContext arg0) throws StartException {
            if (!started.compareAndSet(false, true)) {
                throw new StartException("The service is still started!");
            }
            LOGGER.info("Start HASingleton timer service '" + this.getClass().getName() + "'");
    
            final String node = System.getProperty("jboss.node.name");
            try {
                InitialContext ic = new InitialContext();
                ((Scheduler) ic.lookup("global/jboss-cluster-ha-singleton-service/SchedulerBean!org.jboss.as.quickstarts.cluster.hasingleton.service.ejb.Scheduler"))
                    .initialize("HASingleton timer @" + node + " " + new Date());
            } catch (NamingException e) {
                throw new StartException("Could not initialize timer", e);
            }
        }
    
        public void stop(StopContext arg0) {
            if (!started.compareAndSet(true, false)) {
                LOGGER.warning("The service '" + this.getClass().getName() + "' is not active!");
            } else {
                LOGGER.info("Stop HASingleton timer service '" + this.getClass().getName() + "'");
                try {
                    InitialContext ic = new InitialContext();
                    ((Scheduler) ic.lookup("global/jboss-cluster-ha-singleton-service/SchedulerBean!org.jboss.as.quickstarts.cluster.hasingleton.service.ejb.Scheduler")).stop();
                } catch (NamingException e) {
                    LOGGER.info("Could not stop timer:" + e.getMessage());
                }
            }
        }
    }

  2. Create a service activator that implements the org.jboss.msc.service.ServiceActivator interface and installs the HATimerService as a clustered singleton in the activate() method. This example specifies that node1 should start the singleton service.

    Service Activator Code Example

    public class HATimerServiceActivator implements ServiceActivator {
        private final Logger log = Logger.getLogger(this.getClass().toString());
    
        @Override
        public void activate(ServiceActivatorContext context) {
            log.info("HATimerService will be installed!");
    
            HATimerService service = new HATimerService();
            ServiceName factoryServiceName = SingletonServiceName.BUILDER.getServiceName("server", "default");
            ServiceController<?> factoryService = context.getServiceRegistry().getRequiredService(factoryServiceName);
            SingletonServiceBuilderFactory factory = (SingletonServiceBuilderFactory) factoryService.getValue();
            ServiceName ejbComponentService = ServiceName.of("jboss", "deployment", "unit", "jboss-cluster-ha-singleton-service.jar", "component", "SchedulerBean", "START");
            factory.createSingletonServiceBuilder(HATimerService.SINGLETON_SERVICE_NAME, service)
                .electionPolicy(new PreferredSingletonElectionPolicy(new SimpleSingletonElectionPolicy(), new NamePreference("node1/singleton")))
                .build(new DelegatingServiceContainer(context.getServiceTarget(), context.getServiceRegistry()))
                .setInitialMode(ServiceController.Mode.ACTIVE)
                .addDependency(ejbComponentService)
                .install();
        }
    }

  3. Create a file named org.jboss.msc.service.ServiceActivator in the application’s META-INF/services/ directory and add a line containing the fully qualified name of the ServiceActivator class created in the previous step.

    META-INF/services/org.jboss.msc.service.ServiceActivator File Example

    org.jboss.as.quickstarts.cluster.hasingleton.service.ejb.HATimerServiceActivator

  4. Create a Scheduler interface that contains the initialize() and stop() methods.

    Scheduler Interface Code Example

    public interface Scheduler {
    
        void initialize(String info);
    
        void stop();
    
    }

  5. Create a Singleton bean that implements the Scheduler interface. This bean is used as the cluster-wide singleton timer.

    Important

    The Singleton bean must not have a remote interface and you must not reference its local interface from another EJB in any application. This prevents a lookup by a client or other component and ensures the HATimerService has total control of the Singleton.

    Singleton Bean Code Example

    @Singleton
    public class SchedulerBean implements Scheduler {
        private static Logger LOGGER = Logger.getLogger(SchedulerBean.class.toString());
        @Resource
        private TimerService timerService;
    
        @Timeout
        public void scheduler(Timer timer) {
            LOGGER.info("HASingletonTimer: Info=" + timer.getInfo());
        }
    
        @Override
        public void initialize(String info) {
            ScheduleExpression sexpr = new ScheduleExpression();
            // set schedule to every 10 seconds for demonstration
            sexpr.hour("*").minute("*").second("0/10");
            // persistent must be false because the timer is started by the HASingleton service
            timerService.createCalendarTimer(sexpr, new TimerConfig(info, false));
        }
    
        @Override
        public void stop() {
            LOGGER.info("Stop all existing HASingleton timers");
            for (Timer timer : timerService.getTimers()) {
                LOGGER.fine("Stop HASingleton timer: " + timer.getInfo());
                timer.cancel();
            }
        }
    }

See the cluster-ha-singleton quickstart that ships with JBoss EAP for a complete working example of this application. The quickstart provides detailed instructions to build and deploy the application.

6.5. HA Singleton Deployments

JBoss EAP 7 adds the ability to deploy a given application as a singleton deployment.

When deployed to a group of clustered servers, a singleton deployment will only deploy on a single node at any given time. If the node on which the deployment is active stops or fails, the deployment will automatically start on another node.

The policies for controlling HA singleton behavior are managed by a new singleton subsystem. A deployment may either specify a specific singleton policy or use the default subsystem policy. A deployment identifies itself as singleton deployment via a /META-INF/singleton-deployment.xml deployment descriptor which is most easily applied to an existing deployment as a deployment overlay. Alternatively, the requisite singleton configuration can be embedded within an existing jboss-all.xml.

Defining or Choosing a Singleton Deployment

  • To define a deployment as a singleton deployment, include a /META-INF/singleton-deployment.xml descriptor in your application archive.

    Example of a Singleton Deployment Descriptor:

    <?xml version="1.0" encoding="UTF-8"?>
    <singleton-deployment xmlns="urn:jboss:singleton-deployment:1.0"/>

    Example of a Singleton Deployment Descriptor with a specific singleton policy:

    <?xml version="1.0" encoding="UTF-8"?>
    <singleton-deployment policy="my-new-policy" xmlns="urn:jboss:singleton-deployment:1.0"/>
  • Alternatively, you can also add a singleton-deployment element to your jboss-all.xml descriptor.

    Example of singleton-deployment element in jboss-all.xml:

    <?xml version="1.0" encoding="UTF-8"?>
    <jboss xmlns="urn:jboss:1.0">
        <singleton-deployment xmlns="urn:jboss:singleton-deployment:1.0"/>
    </jboss>

    Example of singleton-deployment element in jboss-all.xml with a specific singleton policy:

    <?xml version="1.0" encoding="UTF-8"?>
    <jboss xmlns="urn:jboss:1.0">
        <singleton-deployment policy="my-new-policy" xmlns="urn:jboss:singleton-deployment:1.0"/>
    </jboss>

Creating a Singleton Deployment

JBoss EAP provides two election policies:

  • Simple Election Policy

    The simple-election-policy chooses a specific member, indicated by the position attribute, on which a given application will be deployed. The position attribute determines the index of the node to be elected from a list of candidates sorted by descending age, where 0 indicates the oldest node, 1 indicates the second oldest node, -1 indicates the youngest node, -2 indicates the second youngest node, and so on. If the specified position exceeds the number of candidates, a modulus operation is applied.

    Example of creating a new singleton policy with a simple-election-policy and position set to -1, using the management CLI:

    batch
    /subsystem=singleton/singleton-policy=my-new-policy:add(cache-container=server)
    /subsystem=singleton/singleton-policy=my-new-policy/election-
    policy=simple:add(position=-1)
    run-batch
    Note

    To set the newly created policy my-new-policy as the default, run this command:

    /subsystem=singleton:write-attribute(name=default, value=my-new-policy)

    Example of configuring a simple-election-policy with position set to -1 using standalone-ha.xml:

    <subsystem xmlns="urn:jboss:domain:singleton:1.0">
       <singleton-policies default="my-new-policy">
          <singleton-policy name="my-new-policy" cache-container="server">
             <simple-election-policy position="-1"/>
          </singleton-policy>
       </singleton-policies>
    </subsystem>
  • Random Election Policy

    The random-election-policy chooses a random member on which a given application will be deployed.

    Example of creating a new singleton policy with a random-election-policy, using the management CLI:

    batch
    /subsystem=singleton/singleton-policy=my-other-new-policy:add(cache-container=server)
    /subsystem=singleton/singleton-policy=my-other-new-policy/election-policy=random:add()
    run-batch

    Example of configuring a random-election-policy using standalone-ha.xml:

    <subsystem xmlns="urn:jboss:domain:singleton:1.0">
       <singleton-policies default="my-other-new-policy">
          <singleton-policy name="my-other-new-policy" cache-container="server">
             <random-election-policy/>
          </singleton-policy>
       </singleton-policies>
    </subsystem>
    Note

    The default-cache attribute of the cache-container needs to be defined before trying to add the policy. Without this, if you are using a custom cache container, you might end up getting error messages.

Preferences

Additionally, any singleton election policy may indicate a preference for one or more members of a cluster. Preferences may be defined either via node name or via outbound socket binding name. Node preferences always take precedent over the results of an election policy.

Example of indicating preference in the existing singleton policy using the management CLI:

/subsystem=singleton/singleton-policy=foo/election-policy=simple:list-add(name=name-preferences, value=nodeA)

/subsystem=singleton/singleton-policy=bar/election-policy=random:list-add(name=socket-binding-preferences, value=binding1)

Example of creating a new singleton policy with a simple-election-policy and name-preferences, using the management CLI:

batch
/subsystem=singleton/singleton-policy=my-new-policy:add(cache-container=server)
/subsystem=singleton/singleton-policy=my-new-policy/election-policy=simple:add(name-preferences=[node1, node2, node3, node4])
run-batch
Note

To set the newly created policy my-new-policy as the default, run this command:

/subsystem=singleton:write-attribute(name=default, value=my-new-policy)

Example of configuring a random-election-policy with socket-binding-preferences using standalone-ha.xml:

<subsystem xmlns="urn:jboss:domain:singleton:1.0">
   <singleton-policies default="my-other-new-policy">
      <singleton-policy name="my-other-new-policy" cache-container="server">
         <random-election-policy>
            <socket-binding-preferences>binding1 binding2 binding3 binding4</socket-binding-preferences>
         </random-election-policy>
      </singleton-policy>
   </singleton-policies>
</subsystem>
Quorum

Network partitions are particularly problematic for singleton deployments, since they can trigger multiple singleton providers for the same deployment to run at the same time. To defend against this scenario, a singleton policy may define a quorum that requires a minimum number of nodes to be present before a singleton provider election can take place. A typical deployment scenario uses a quorum of N/2 + 1, where N is the anticipated cluster size. This value can be updated at runtime, and will immediately affect any singleton deployments using the respective singleton policy.

Example of quorum declaration in the standalone-ha.xml file:

<subsystem xmlns="urn:jboss:domain:singleton:1.0">
   <singleton-policies default="default">
      <singleton-policy name="default" cache-container="server" quorum="4">
         <simple-election-policy/>
      </singleton-policy>
   </singleton-policies>
</subsystem>

Example of quorum declaration using the management CLI:

/subsystem=singleton/singleton-policy=foo:write-attribute(name=quorum, value=3)

6.6. Apache mod_cluster-manager Application

6.6.1. About mod_cluster-manager Application

The mod_cluster-manager application is an administration web page, which is available on Apache HTTP Server. It is used for monitoring the connected worker nodes and performing various administration tasks, such as enabling or disabling contexts, and configuring the load-balancing properties of worker nodes in a cluster.

Exploring mod_cluster-manager Application

The mod_cluster-manager application can be used for performing various administration tasks on worker nodes.

mod_cluster Administration Web Page Figure - mod_cluster Administration Web Page

  • [1] mod_cluster/1.3.1.Final: The version of the mod_cluster native library.
  • [2] ajp://192.168.122.204:8099: The protocol used (either AJP, HTTP, or HTTPS), hostname or IP address of the worker node, and the port.
  • [3] jboss-eap-7.0-2: The worker node’s JVMRoute.
  • [4] Virtual Host 1: The virtual host(s) configured on the worker node.
  • [5] Disable: An administration option that can be used to disable the creation of new sessions on the particular context. However, the ongoing sessions do not get disabled and remain intact.
  • [6] Stop: An administration option that can be used to stop the routing of session requests to the context. The remaining sessions will failover to another node unless the sticky-session-force property is set to true.
  • [7] Enable Contexts Disable Contexts Stop Contexts: The operations that can be performed on the whole node. Selecting one of these options affects all the contexts of a node in all its virtual hosts.
  • [8] Load balancing group (LBGroup): The load-balancing-group property is set in the modcluster subsystem in JBoss EAP configuration to group all worker nodes into custom load balancing groups. Load balancing group (LBGroup) is an informational field that gives information about all set load balancing groups. If this field is not set, then all worker nodes are grouped into a single default load balancing group.

    Note

    This is only an informational field and thus cannot be used to set load-balancing-group property. The property has to be set in modcluster subsystem in JBoss EAP configuration.

  • [9] Load (value): The load factor on the worker node. The load factor(s) are evaluated as below:

    -load > 0 : A load factor with value 1 indicates that the worker node is overloaded. A load factor of 100 denotes a free and not-loaded node.
    -load = 0 : A load factor of value 0 indicates that the worker node is in standby mode. This means that no session requests will be routed to this node until and unless the other worker nodes are unavailable.
    -load = -1 : A load factor of value -1 indicates that the worker node is in an error state.
    -load = -2 : A load factor of value -2 indicates that the worker node is undergoing CPing/CPong and is in a transition state.
Note

For JBoss EAP 7.0, it is also possible to use Undertow as load balancer.

Chapter 7. Contexts and Dependency Injection (CDI)

7.1. Introduction to CDI

7.1.1. About Contexts and Dependency Injection (CDI)

Contexts and Dependency Injection (CDI) 1.2 is a specification designed to enable Enterprise Java Beans (EJB) 3 components to be used as Java Server Faces (JSF) managed beans. CDI unifies the two component models and enables a considerable simplification to the programming model for web-based applications in Java. CDI 1.2 release is treated as a maintenance release of 1.1. Details about CDI 1.1 can be found in JSR 346: Contexts and Dependency Injection for Java™ EE 1.1.

JBoss EAP includes Weld, which is the reference implementation of JSR-346:Contexts and Dependency Injection for Java™ EE 1.1.

Benefits of CDI

The benefits of CDI include:

  • Simplifying and shrinking your code base by replacing big chunks of code with annotations.
  • Flexibility, allowing you to disable and enable injections and events, use alternative beans, and inject non-CDI objects easily.
  • Optionally, allowing you to include beans.xml in your META-INF/ or WEB-INF/ directory if you need to customize the configuration to differ from the default. The file can be empty.
  • Simplifying packaging and deployments and reducing the amount of XML you need to add to your deployments.
  • Providing lifecycle management via contexts. You can tie injections to requests, sessions, conversations, or custom contexts.
  • Providing type-safe dependency injection, which is safer and easier to debug than string-based injection.
  • Decoupling interceptors from beans.
  • Providing complex event notification.

7.1.2. Relationship Between Weld, Seam 2, and JavaServer Faces

Weld is the reference implementation of CDI, which is defined in JSR 346: Contexts and Dependency Injection for Java™ EE 1.1. Weld was inspired by Seam 2 and other dependency injection frameworks, and is included in JBoss EAP.

The goal of Seam 2 was to unify Enterprise Java Beans and JavaServer Faces managed beans.

JavaServer Faces 2.2 implements JSR-344: JavaServer™ Faces 2.2. It is an API for building server-side user interfaces.

7.2. Enable CDI

CDI is one of the core technologies in JBoss EAP and is enabled by default. CDI may have been disabled by commenting out or removing the relevant sections of the configuration file. Use the following procedure if you need to enable it.

Enable CDI in JBoss EAP

  1. Stop JBoss EAP.

    JBoss EAP modifies the configuration files when running, so stop the server before editing the configuration files directly.

  2. Edit the appropriate configuration file.

    Edit the EAP_HOME/standalone/configuration/standalone.xml for a standalone server or EAP_HOME/domain/configuration/domain.xml for a managed domain.

  3. Add the CDI extension.

    If the org.jboss.as.weld extension was commented out, uncomment it. If it was removed entirely, restore it by adding the following line to the file in a new line directly above the </extensions> tag.

    <extension module="org.jboss.as.weld"/>
  4. Add the CDI subsystem.

    If the weld subsystem was commented out, uncomment it. If it was removed entirely, restore it by adding the following line to the relevant profile in the <profiles> section.

    <subsystem xmlns="urn:jboss:domain:weld:3.0"/>
  5. Start JBoss EAP with your updated configuration.

When JBoss EAP starts, the CDI subsystem will be enabled.

7.3. Use CDI to Develop an Application

Contexts and Dependency Injection (CDI) gives you tremendous flexibility in developing applications, reusing code, adapting your code at deployment or run-time, and unit testing. JBoss EAP includes Weld, the reference implementation of CDI. These tasks show you how to use CDI in your enterprise applications.

7.3.1. Default Bean Discovery Mode

The default bean discovery mode for a bean archive is annotated. Such a bean archive is said to be an implicit bean archive.

If the bean discovery mode is annotated then:

  • Bean classes that do not have bean defining annotation and are not bean classes of sessions beans are not discovered.
  • Producer methods that are not on a session bean and whose bean class does not have a bean defining annotation are not discovered.
  • Producer fields that are not on a session bean and whose bean class does not have a bean defining annotation are not discovered.
  • Disposer methods that are not on a session bean and whose bean class does not have a bean defining annotation are not discovered.
  • Observer methods that are not on a session bean and whose bean class does not have a bean defining annotation are not discovered.
Important

All examples in the CDI section are valid only when you have a discovery mode set to all.

Bean Defining Annotations

A bean class may have a bean defining annotation, allowing it to be placed anywhere in an application, as defined in Bean archives. A bean class with a bean defining annotation is said to be an implicit bean.

The set of bean defining annotations contains:

  • @ApplicationScoped, @SessionScoped, @ConversationScoped and @RequestScoped annotations
  • All other normal scope types
  • @Interceptor and @Decorator annotations
  • All stereotype annotations, i.e. annotations annotated with @Stereotype
  • The @Dependent scope annotation

If one of these annotations is declared on a bean class, then the bean class is said to have a bean defining annotation. For example, this dependent scoped bean has a bean defining annotation:

@Dependent
public class BookShop
        extends Business
        implements Shop<Book> {
    ...
}
Note

To ensure compatibility with other JSR-330 implementations, all pseudo-scope annotations, except @Dependent, are not bean defining annotations. However, a stereotype annotation including a pseudo-scope annotation is a bean defining annotation.

7.3.2. Exclude Beans From the Scanning Process

Exclude filters are defined by <exclude> elements in the beans.xml file for the bean archive as children of the <scan> element. By default an exclude filter is active. The exclude filter becomes inactive, if its definition contains:

  • A child element named <if-class-available> with a name attribute, and the class loader for the bean archive can not load a class for that name, or
  • A child element named <if-class-not-available> with a name attribute, and the class loader for the bean archive can load a class for that name, or
  • A child element named <if-system-property> with a name attribute, and there is no system property defined for that name, or
  • A child element named <if-system-property> with a name attribute and a value attribute, and there is no system property defined for that name with that value.

The type is excluded from discovery, if the filter is active, and:

  • The fully qualified name of the type being discovered matches the value of the name attribute of the exclude filter, or
  • The package name of the type being discovered matches the value of the name attribute with a suffix ".*" of the exclude filter, or
  • The package name of the type being discovered starts with the value of the name attribute with a suffix ".**" of the exclude filter

For example, consider the following beans.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://xmlns.jcp.org/xml/ns/javaee">

    <scan>
        <exclude name="com.acme.rest.*" /> 1

        <exclude name="com.acme.faces.**"> 2
            <if-class-not-available name="javax.faces.context.FacesContext"/>
        </exclude>

        <exclude name="com.acme.verbose.*"> 3
            <if-system-property name="verbosity" value="low"/>
        </exclude>

        <exclude name="com.acme.ejb.**"> 4
            <if-class-available name="javax.enterprise.inject.Model"/>
            <if-system-property name="exclude-ejbs"/>
        </exclude>
    </scan>

</beans>
1
The first exclude filter will exclude all classes in com.acme.rest package.
2
The second exclude filter will exclude all classes in the com.acme.faces package, and any subpackages, but only if JSF is not available.
3
The third exclude filter will exclude all classes in the com.acme.verbose package if the system property verbosity has the value low.
4
The fourth exclude filter will exclude all classes in the com.acme.ejb package, and any subpackages, if the system property exclude-ejbs is set with any value and if at the same time, the javax.enterprise.inject.Model class is also available to the classloader.
Note

It is safe to annotate Java EE components with @Vetoed to prevent them being considered beans. An event is not fired for any type annotated with @Vetoed, or in a package annotated with @Vetoed. For more information, see @Vetoed.

7.3.3. Use an Injection to Extend an Implementation

You can use an injection to add or change a feature of your existing code.

The following example adds a translation ability to an existing class, and assumes you already have a Welcome class, which has a method buildPhrase. The buildPhrase method takes as an argument the name of a city, and outputs a phrase like "Welcome to Boston!".

Example: Inject a Translator Bean Into the Welcome Class

The following injects a hypothetical Translator object into the Welcome class. The Translator object can be an EJB stateless bean or another type of bean, which can translate sentences from one language to another. In this instance, the Translator is used to translate the entire greeting, without modifying the original Welcome class. The Translator is injected before the buildPhrase method is called.

public class TranslatingWelcome extends Welcome {

    @Inject Translator translator;

    public String buildPhrase(String city) {
        return translator.translate("Welcome to " + city + "!");
    }
    ...
}

7.4. Ambiguous or Unsatisfied Dependencies

Ambiguous dependencies exist when the container is unable to resolve an injection to exactly one bean.

Unsatisfied dependencies exist when the container is unable to resolve an injection to any bean at all.

The container takes the following steps to try to resolve dependencies:

  1. It resolves the qualifier annotations on all beans that implement the bean type of an injection point.
  2. It filters out disabled beans. Disabled beans are @Alternative beans which are not explicitly enabled.

In the event of an ambiguous or unsatisfied dependency, the container aborts deployment and throws an exception.

To fix an ambiguous dependency, see Use a Qualifier to Resolve an Ambiguous Injection.

7.4.1. Qualifiers

Qualifiers are annotations used to avoid ambiguous dependencies when the container can resolve multiple beans, which fit into an injection point. A qualifier declared at an injection point provides the set of eligible beans, which declare the same Qualifier.

Qualifiers have to be declared with a retention and target as shown in the example below.

Example: Define the @Synchronous and @Asynchronous Qualifiers

@Qualifier
@Retention(RUNTIME)
@Target({TYPE, METHOD, FIELD, PARAMETER})
public @interface Synchronous {}

@Qualifier
@Retention(RUNTIME)
@Target({TYPE, METHOD, FIELD, PARAMETER})
public @interface Asynchronous {}

Example: Use the @Synchronous and @Asynchronous Qualifiers

@Synchronous
public class SynchronousPaymentProcessor implements PaymentProcessor {
   public void process(Payment payment) { ... }
}

@Asynchronous
public class AsynchronousPaymentProcessor implements PaymentProcessor {
   public void process(Payment payment) { ... }
}
'@Any'

Whenever a bean or injection point does not explicitly declare a qualifier, the container assumes the qualifier @Default. From time to time, you will need to declare an injection point without specifying a qualifier. There is a qualifier for that too. All beans have the qualifier @Any. Therefore, by explicitly specifying @Any at an injection point, you suppress the default qualifier, without otherwise restricting the beans that are eligible for injection.

This is especially useful if you want to iterate over all beans with a certain bean type.

import javax.enterprise.inject.Instance;
...

@Inject

void initServices(@Any Instance<Service> services) {

   for (Service service: services) {

      service.init();

   }

}

Every bean has the qualifier @Any, even if it does not explicitly declare this qualifier.

Every event also has the qualifier @Any, even if it was raised without explicit declaration of this qualifier.

@Inject @Any Event<User> anyUserEvent;

The @Any qualifier allows an injection point to refer to all beans or all events of a certain bean type.

@Inject @Delegate @Any Logger logger;

7.4.2. Use a Qualifier to Resolve an Ambiguous Injection

You can resolve an ambiguous injection using a qualifier. Read more about ambiguous injections at Ambiguous or Unsatisfied Dependencies.

The following example is ambiguous and features two implementations of Welcome, one which translates and one which does not. The injection needs to be specified to use the translating Welcome.

Example: Ambiguous injection

public class Greeter {
  private Welcome welcome;

  @Inject
  void init(Welcome welcome) {
    this.welcome = welcome;
  }
  ...
}

Resolve an Ambiguous Injection with a Qualifier
  1. To resolve the ambiguous injection, create a qualifier annotation called @Translating:

    @Qualifier
    @Retention(RUNTIME)
    @Target({TYPE,METHOD,FIELD,PARAMETERS})
    public @interface Translating{}
  2. Annotate your translating Welcome with the @Translating annotation:

    @Translating
    public class TranslatingWelcome extends Welcome {
        @Inject Translator translator;
        public String buildPhrase(String city) {
            return translator.translate("Welcome to " + city + "!");
        }
        ...
    }
  3. Request the translating Welcome in your injection. You must request a qualified implementation explicitly, similar to the factory method pattern. The ambiguity is resolved at the injection point.

    public class Greeter {
      private Welcome welcome;
      @Inject
      void init(@Translating Welcome welcome) {
        this.welcome = welcome;
      }
      public void welcomeVisitors() {
        System.out.println(welcome.buildPhrase("San Francisco"));
      }
    }

7.5. Managed Beans

Java EE establishes a common definition in the Managed Beans specification. Managed Beans are defined as container-managed objects with minimal programming restrictions, otherwise known by the acronym POJO (Plain Old Java Object). They support a small set of basic services, such as resource injection, lifecycle callbacks, and interceptors. Companion specifications, such as EJB and CDI, build on this basic model.

With very few exceptions, almost every concrete Java class that has a constructor with no parameters (or a constructor designated with the annotation @Inject) is a bean. This includes every JavaBean and every EJB session bean.

7.5.1. Types of Classes That are Beans

A managed bean is a Java class. The basic lifecycle and semantics of a managed bean are defined by the Managed Beans specification. You can explicitly declare a managed bean by annotating the bean class @ManagedBean, but in CDI you do not need to. According to the specification, the CDI container treats any class that satisfies the following conditions as a managed bean:

  • It is not a non-static inner class.
  • It is a concrete class, or is annotated @Decorator.
  • It is not annotated with an EJB component-defining annotation or declared as an EJB bean class in ejb-jar.xml.
  • It does not implement interface javax.enterprise.inject.spi.Extension.
  • It has either a constructor with no parameters, or a constructor annotated with @Inject.
  • It is not annotated @Vetoed or in a package annotated @Vetoed .

The unrestricted set of bean types for a managed bean contains the bean class, every superclass and all interfaces it implements directly or indirectly.

If a managed bean has a public field, it must have the default scope @Dependent.

@Vetoed

CDI 1.1 introduces a new annotation, @Vetoed. You can prevent a bean from injection by adding this annotation:

@Vetoed
public class SimpleGreeting implements Greeting {
    ...
}

In this code, the SimpleGreeting bean is not considered for injection.

All beans in a package may be prevented from injection:

@Vetoed
package org.sample.beans;

import javax.enterprise.inject.Vetoed;

This code in package-info.java in the org.sample.beans package will prevent all beans inside this package from injection.

Java EE components, such as stateless EJBs or JAX-RS resource endpoints, can be marked with @Vetoed to prevent them from being considered beans. Adding the @Vetoed annotation to all persistent entities prevents the BeanManager from managing an entity as a CDI Bean. When an entity is annotated @Vetoed, no injections take place. The reasoning behind this is to prevent the BeanManager from performing the operations that may cause the JPA provider to break.

7.5.2. Use CDI to Inject an Object Into a Bean

CDI is activated automatically if CDI components are detected in an application. If you wish to customize your configuration to differ from the default, you can include META-INF/beans.xml or WEB-INF/beans.xml to your deployment archive.

Inject Objects into Other Objects
  1. To obtain an instance of a class, annotate the field with @Inject within your bean:

    public class TranslateController {
       @Inject TextTranslator textTranslator;
       ...
  2. Use your injected object’s methods directly. Assume that TextTranslator has a method translate:

    // in TranslateController class
    
    public void translate() {
       translation = textTranslator.translate(inputText);
    }
  3. Use an injection in the constructor of a bean. You can inject objects into the constructor of a bean as an alternative to using a factory or service locator to create them:

    public class TextTranslator {
    
       private SentenceParser sentenceParser;
       private Translator sentenceTranslator;
    
       @Inject
       TextTranslator(SentenceParser sentenceParser, Translator sentenceTranslator) {
          this.sentenceParser = sentenceParser;
          this.sentenceTranslator = sentenceTranslator;
       }
    
       // Methods of the TextTranslator class
       ...
    }
  4. Use the Instance(<T>) interface to get instances programmatically. The Instance interface can return an instance of TextTranslator when parameterized with the bean type.

    @Inject Instance<TextTranslator> textTranslatorInstance;
    ...
    public void translate() {
       textTranslatorInstance.get().translate(inputText);
    }

When you inject an object into a bean, all of the object’s methods and properties are available to your bean. If you inject into your bean’s constructor, instances of the injected objects are created when your bean’s constructor is called, unless the injection refers to an instance that already exists. For instance, a new instance would not be created if you inject a session-scoped bean during the lifetime of the session.

7.6. Contexts and Scopes

A context, in terms of CDI, is a storage area that holds instances of beans associated with a specific scope.

A scope is the link between a bean and a context. A scope/context combination may have a specific lifecycle. Several predefined scopes exist, and you can create your own. Examples of predefined scopes are @RequestScoped, @SessionScoped, and @ConversationScope.

Table 7.1. Available Scopes

ScopeDescription

@Dependent

The bean is bound to the lifecycle of the bean holding the reference. The default scope for an injected bean is @Dependent.

@ApplicationScoped

The bean is bound to the lifecycle of the application.

@RequestScoped

The bean is bound to the lifecycle of the request.

@SessionScoped

The bean is bound to the lifecycle of the session.

@ConversationScoped

The bean is bound to the lifecycle of the conversation. The conversation scope is between the lengths of the request and the session, and is controlled by the application.

Custom scopes

If the above contexts do not meet your needs, you can define custom scopes.

7.7. Named Beans

You can name a bean by using the @Named annotation. Naming a bean allows you to use it directly in Java Server Faces (JSF) and Expression Language (EL).

The @Named annotation takes an optional parameter, which is the bean name. If this parameter is omitted, the bean name defaults to the class name of the bean with its first letter converted to lower-case.

7.7.1. Use Named Beans

Configure Bean Names Using the @Named Annotation
  1. Use the @Named annotation to assign a name to a bean.

    @Named("greeter")
    public class GreeterBean {
      private Welcome welcome;
    
      @Inject
      void init (Welcome welcome) {
        this.welcome = welcome;
      }
    
      public void welcomeVisitors() {
        System.out.println(welcome.buildPhrase("San Francisco"));
      }
    }

    In the example above, the default name would be greeterBean if no name had been specified.

  2. Use the named bean in a JSF view.

    <h:form>
      <h:commandButton value="Welcome visitors" action="#{greeter.welcomeVisitors}"/>
    </h:form>

7.8. Bean Lifecycle

This task shows you how to save a bean for the life of a request.

The default scope for an injected bean is @Dependent. This means that the bean’s lifecycle is dependent upon the lifecycle of the bean that holds the reference. Several other scopes exist, and you can define your own scopes. For more information, see Contexts and Scopes.

Manage Bean Lifecycles

  1. Annotate the bean with the desired scope.

    @RequestScoped
    @Named("greeter")
    public class GreeterBean {
      private Welcome welcome;
      private String city; // getter & setter not shown
      @Inject   void init(Welcome welcome) {
        this.welcome = welcome;
      }
      public void welcomeVisitors() {
        System.out.println(welcome.buildPhrase(city));
      }
    }
  2. When your bean is used in the JSF view, it holds state.

    <h:form>
      <h:inputText value="#{greeter.city}"/>
      <h:commandButton value="Welcome visitors" action="#{greeter.welcomeVisitors}"/>
    </h:form>

Your bean is saved in the context relating to the scope that you specify, and lasts as long as the scope applies.

7.8.1. Use a Producer Method

A producer method is a method that acts as a source of bean instances. When no instance exists in the specified context, the method declaration itself describes the bean, and the container invokes the method to obtain an instance of the bean. A producer method lets the application take full control of the bean instantiation process.

This task shows how to use producer methods to produce a variety of different objects that are not beans for injection.

Example: Use a producer method instead of an alternative, to allow polymorphism after deployment

The @Preferred annotation in the example is a qualifier annotation. For more information about qualifiers, see Qualifiers.

@SessionScoped
public class Preferences implements Serializable {
   private PaymentStrategyType paymentStrategy;
   ...
   @Produces @Preferred
   public PaymentStrategy getPaymentStrategy() {
       switch (paymentStrategy) {
           case CREDIT_CARD: return new CreditCardPaymentStrategy();
           case CHECK: return new CheckPaymentStrategy();
           default: return null;
       }
   }
}

The following injection point has the same type and qualifier annotations as the producer method, so it resolves to the producer method using the usual CDI injection rules. The producer method is called by the container to obtain an instance to service this injection point.

@Inject @Preferred PaymentStrategy paymentStrategy;

Example: Assign a scope to a producer method

The default scope of a producer method is @Dependent. If you assign a scope to a bean, it is bound to the appropriate context. The producer method in this example is only called once per session.

@Produces @Preferred @SessionScoped
public PaymentStrategy getPaymentStrategy() {
   ...
}

Example: Use an injection inside a producer method

Objects instantiated directly by an application cannot take advantage of dependency injection and do not have interceptors. However, you can use dependency injection into the producer method to obtain bean instances.

@Produces @Preferred @SessionScoped
public PaymentStrategy getPaymentStrategy(CreditCardPaymentStrategy ccps,
                                          CheckPaymentStrategy cps ) {
   switch (paymentStrategy) {
      case CREDIT_CARD: return ccps;
      case CHEQUE: return cps;
      default: return null;
   }
}

If you inject a request-scoped bean into a session-scoped producer, the producer method promotes the current request-scoped instance into session scope. This is almost certainly not the desired behavior, so use caution when you use a producer method in this way.

Note

The scope of the producer method is not inherited from the bean that declares the producer method.

Producer methods allow you to inject non-bean objects and change your code dynamically.

7.9. Alternative Beans

Alternatives are beans whose implementation is specific to a particular client module or deployment scenario.

By default, @Alternative beans are disabled. They are enabled for a specific bean archive by editing its beans.xml file. However, this activation only applies to the beans in that archive. From CDI 1.1 onwards, the alternative can be enabled for the entire application using the @Priority annotation.

Example of Defining Alternatives

This alternative defines an implementation of the PaymentProcessor class using both @Synchronous and @Asynchronous alternatives:

@Alternative @Synchronous @Asynchronous

public class MockPaymentProcessor implements PaymentProcessor {

   public void process(Payment payment) { ... }

}

Example of Enabling @Alternative using beans.xml

<beans
   xmlns="http://xmlns.jcp.org/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="
      http://xmlns.jcp.org/xml/ns/javaee
      http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd">
   <alternatives>
         <class>org.mycompany.mock.MockPaymentProcessor</class>
   </alternatives>
</beans>

Declaring Selected Alternatives

The @Priority annotation allows an alternative to be enabled for an entire application. An alternative may be given a priority for the application:

  • by placing the @Priority annotation on the bean class of a managed bean or session bean, or
  • by placing the @Priority annotation on the bean class that declares the producer method, field or resource.

7.9.1. Override an Injection with an Alternative

You can use alternative beans to override existing beans. They can be thought of as a way to plug in a class which fills the same role, but functions differently. They are disabled by default.

This task shows you how to specify and enable an alternative.

Override an Injection

This task assumes that you already have a TranslatingWelcome class in your project, but you want to override it with a "mock" TranslatingWelcome class. This would be the case for a test deployment, where the true Translator bean cannot be used.

  1. Define the alternative.

    @Alternative
    @Translating
    public class MockTranslatingWelcome extends Welcome {
      public String buildPhrase(string city) {
        return "Bienvenue à " + city + "!");
      }
    }
  2. Activate the substitute implementation by adding the fully-qualified class name to your META-INF/beans.xml or WEB-INF/beans.xml file.

    <beans>
      <alternatives>
        <class>com.acme.MockTranslatingWelcome</class>
      </alternatives>
    </beans>

The alternative implementation is now used instead of the original one.

7.10. Stereotypes

In many systems, use of architectural patterns produces a set of recurring bean roles. A stereotype allows you to identify such a role and declare some common metadata for beans with that role in a central place.

A stereotype encapsulates any combination of:

  • Default scope
  • A set of interceptor bindings

A stereotype can also specify either:

  • All beans where the stereotypes are defaulted bean EL names
  • All beans where the stereotypes are alternatives

A bean may declare zero, one, or multiple stereotypes. A stereotype is an @Stereotype annotation that packages several other annotations. Stereotype annotations may be applied to a bean class, producer method, or field.

A class that inherits a scope from a stereotype may override that stereotype and specify a scope directly on the bean.

In addition, if a stereotype has a @Named annotation, any bean it is placed on has a default bean name. The bean may override this name if the @Named annotation is specified directly on the bean. For more information about named beans, see Named Beans.

7.10.1. Use Stereotypes

Without stereotypes, annotations can become cluttered. This task shows you how to use stereotypes to reduce the clutter and streamline your code.

Example: Annotation clutter

@Secure
@Transactional
@RequestScoped
@Named
public class AccountManager {
  public boolean transfer(Account a, Account b) {
    ...
  }
}

Define and Use Stereotypes
  1. Define the stereotype.

    @Secure
    @Transactional
    @RequestScoped
    @Named
    @Stereotype
    @Retention(RUNTIME)
    @Target(TYPE)
    public @interface BusinessComponent {
     ...
    }
  2. Use the stereotype.

    @BusinessComponent
    public class AccountManager {
      public boolean transfer(Account a, Account b) {
        ...
      }
    }

7.11. Observer Methods

Observer methods receive notifications when events occur.

CDI also provides transactional observer methods, which receive event notifications during the before completion or after completion phase of the transaction in which the event was fired.

7.11.1. Fire and Observe Events

Example: Fire an event

The following code shows an event being injected and used in a method.

public class AccountManager {
  @Inject Event<Withdrawal> event;

  public boolean transfer(Account a, Account b) {
    ...
    event.fire(new Withdrawal(a));
  }
}

Example: Fire an event with a qualifier

You can annotate your event injection with a qualifier, to make it more specific. For more information about qualifiers, see Qualifiers.

public class AccountManager {
  @Inject @Suspicious Event <Withdrawal> event;

  public boolean transfer(Account a, Account b) {
    ...
    event.fire(new Withdrawal(a));
  }
}

Example: Observe an event

To observe an event, use the @Observes annotation.

public class AccountObserver {
  void checkTran(@Observes Withdrawal w) {
    ...
  }
}

You can use qualifiers to observe only specific types of events.

public class AccountObserver {
  void checkTran(@Observes @Suspicious Withdrawal w) {
    ...
  }
}

7.11.2. Transactional Observers

Transactional observers receive the event notifications before or after the completion phase of the transaction in which the event was raised. Transactional observers are important in a stateful object model because state is often held for longer than a single atomic transaction.

There are five kinds of transactional observers:

  • IN_PROGRESS: By default, observers are invoked immediately.
  • AFTER_SUCCESS: Observers are invoked after the completion phase of the transaction, but only if the transaction completes successfully.
  • AFTER_FAILURE: Observers are invoked after the completion phase of the transaction, but only if the transaction fails to complete successfully.
  • AFTER_COMPLETION: Observers are invoked after the completion phase of the transaction.
  • BEFORE_COMPLETION: Observers are invoked before the completion phase of the transaction.

The following observer method refreshes a query result set cached in the application context, but only when transactions that update the Category tree are successful:

public void refreshCategoryTree(@Observes(during = AFTER_SUCCESS) CategoryUpdateEvent event) { ... }

Assume we have cached a JPA query result set in the application scope:

import javax.ejb.Singleton;
import javax.enterprise.inject.Produces;

@ApplicationScoped @Singleton

public class Catalog {
   @PersistenceContext EntityManager em;
   List<Product> products;
   @Produces @Catalog
   List<Product> getCatalog() {
      if (products==null) {
         products = em.createQuery("select p from Product p where p.deleted = false")
            .getResultList();
      }
      return products;
   }
}

Occasionally a Product is created or deleted. When this occurs, we need to refresh the Product catalog. But we have to wait for the transaction to complete successfully before performing this refresh.

The bean that creates and deletes Products triggers events, for example:

import javax.enterprise.event.Event;

@Stateless

public class ProductManager {
   @PersistenceContext EntityManager em;
   @Inject @Any Event<Product> productEvent;
   public void delete(Product product) {
      em.delete(product);
      productEvent.select(new AnnotationLiteral<Deleted>(){}).fire(product);
   }

   public void persist(Product product) {
      em.persist(product);
      productEvent.select(new AnnotationLiteral<Created>(){}).fire(product);
   }
   ...
}

The Catalog can now observe the events after successful completion of the transaction:

import javax.ejb.Singleton;

@ApplicationScoped @Singleton
public class Catalog {
   ...
   void addProduct(@Observes(during = AFTER_SUCCESS) @Created Product product) {
      products.add(product);
   }

   void removeProduct(@Observes(during = AFTER_SUCCESS) @Deleted Product product) {
      products.remove(product);
   }

}

7.12. Interceptors

Interceptors allow you to add functionality to the business methods of a bean without modifying the bean’s method directly. The interceptor is executed before any of the business methods of the bean. Interceptors are defined as part of the JSR 318: Enterprise JavaBeans™ 3.1 specification.

CDI enhances this functionality by allowing you to use annotations to bind interceptors to beans.

Interception points

  • Business method interception: A business method interceptor applies to invocations of methods of the bean by clients of the bean.
  • Lifecycle callback interception: A lifecycle callback interceptor applies to invocations of lifecycle callbacks by the container.
  • Timeout method interception: A timeout method interceptor applies to invocations of the EJB timeout methods by the container.

Enabling Interceptors

By default, all interceptors are disabled. You can enable the interceptor by using the beans.xml descriptor of a bean archive. However, this activation only applies to the beans in that archive. From CDI 1.1 onwards the interceptor can be enabled for the whole application using the @Priority annotation.

<beans
   xmlns="http://xmlns.jcp.org/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="
      http://xmlns.jcp.org/xml/ns/javaee
      http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd">
   <interceptors>
      <class>org.mycompany.myapp.TransactionInterceptor</class>
   </interceptors>
</beans>

Having the XML declaration solves two problems:

  • It enables us to specify an ordering for the interceptors in our system, ensuring deterministic behavior
  • It lets us enable or disable interceptor classes at deployment time.

Interceptors enabled using @Priority are called before interceptors enabled using the beans.xml file.

Note

Having an interceptor enabled by @Priority and at the same time invoked by beans.xml, leads to a non-portable behavior. This combination of enablement should therefore be avoided in order to maintain consistent behavior across different CDI implementations.

7.12.1. Use Interceptors with CDI

CDI can simplify your interceptor code and make it easier to apply to your business code.

Without CDI, interceptors have two problems:

  • The bean must specify the interceptor implementation directly.
  • Every bean in the application must specify the full set of interceptors in the correct order. This makes adding or removing interceptors on an application-wide basis time-consuming and error-prone.

Example: Interceptors without CDI

@Interceptors({
  SecurityInterceptor.class,
  TransactionInterceptor.class,
  LoggingInterceptor.class
})
@Stateful public class BusinessComponent {
  ...
}

Use interceptors with CDI
  1. Define the interceptor binding type:

    @InterceptorBinding
    @Retention(RUNTIME)
    @Target({TYPE, METHOD})
    public @interface Secure {}
  2. Mark the interceptor implementation:

    @Secure
    @Interceptor
    public class SecurityInterceptor {
      @AroundInvoke
      public Object aroundInvoke(InvocationContext ctx) throws Exception {
        // enforce security ...
        return ctx.proceed();
        }
    }
  3. Use the interceptor in your business code:

    @Secure
    public class AccountManager {
      public boolean transfer(Account a, Account b) {
        ...
      }
    }
  4. Enable the interceptor in your deployment, by adding it to META-INF/beans.xml or WEB-INF/beans.xml:

    <beans>
      <interceptors>
        <class>com.acme.SecurityInterceptor</class>
        <class>com.acme.TransactionInterceptor</class>
      </interceptors>
    </beans>

The interceptors are applied in the order listed.

7.13. Decorators

A decorator intercepts invocations from a specific Java interface, and is aware of all the semantics attached to that interface. Decorators are useful for modeling some kinds of business concerns, but do not have the generality of interceptors. A decorator is a bean, or even an abstract class, that implements the type it decorates, and is annotated with @Decorator. To invoke a decorator in a CDI application, it must be specified in the beans.xml file.

Example of invoking a decorator through beans.xml

<beans
   xmlns="http://xmlns.jcp.org/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="
      http://xmlns.jcp.org/xml/ns/javaee
      http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd">
   <decorators>
         <class>org.mycompany.myapp.LargeTransactionDecorator</class>
   </decorators>
</beans>

This declaration serves two main purposes:

  • It enables us to specify an ordering for decorators in our system, ensuring deterministic behavior
  • It lets us enable or disable decorator classes at deployment time.

A decorator must have exactly one @Delegate injection point to obtain a reference to the decorated object.

An Example Decorator

@Decorator
public abstract class LargeTransactionDecorator implements Account {

   @Inject @Delegate @Any Account account;
   @PersistenceContext EntityManager em;

   public void withdraw(BigDecimal amount) {
      ...
   }

   public void deposit(BigDecimal amount);
      ...
   }
}

From CDI 1.1 onwards, the decorator can be enabled for the whole application using @Priority annotation.

Decorators enabled using @Priority are called before decorators enabled using beans.xml. The lower priority values are called first.

Note

Having a decorator enabled by @Priority and at the same time invoked by beans.xml, leads to a non-portable behavior. This combination of enablement should therefore be avoided in order to maintain consistent behavior across different CDI implementations.

7.14. Portable Extensions

CDI is intended to be a foundation for frameworks, extensions, and for integration with other technologies. Therefore, CDI exposes a set of SPIs for the use of developers of portable extensions to CDI.

Extensions can provide the following types of functionality:

  • Integration with Business Process Management engines
  • Integration with third-party frameworks, such as Spring, Seam, GWT, or Wicket
  • New technology based upon the CDI programming model

According to the JSR-346 specification, a portable extension can integrate with the container in the following ways:

  • Providing its own beans, interceptors, and decorators to the container
  • Injecting dependencies into its own objects using the dependency injection service
  • Providing a context implementation for a custom scope
  • Augmenting or overriding the annotation-based metadata with metadata from another source

7.15. Bean Proxies

Clients of an injected bean do not usually hold a direct reference to a bean instance. Unless the bean is a dependent object, scope @Dependent, the container must redirect all injected references to the bean using a proxy object.

A bean proxy, which can be referred to as client proxy, is responsible for ensuring the bean instance that receives a method invocation is the instance associated with the current context. The client proxy also allows beans bound to contexts, such as the session context, to be serialized to disk without recursively serializing other injected beans.

Due to Java limitations, some Java types cannot be proxied by the container. If an injection point declared with one of these types resolves to a bean with a scope other than @Dependent, the container aborts the deployment.

Certain Java types cannot be proxied by the container. These include:

  • Classes that do not have a non-private constructor with no parameters
  • Classes that are declared final or have a final method
  • Arrays and primitive types

7.16. Use a Proxy in an Injection

A proxy is used for injection when the lifecycles of the beans are different from each other. The proxy is a subclass of the bean that is created at run-time, and overrides all the non-private methods of the bean class. The proxy forwards the invocation onto the actual bean instance.

In this example, the PaymentProcessor instance is not injected directly into Shop. Instead, a proxy is injected, and when the processPayment() method is called, the proxy looks up the current PaymentProcessor bean instance and calls the processPayment() method on it.

Example: Proxy Injection

@ConversationScoped
class PaymentProcessor
{
  public void processPayment(int amount)
  {
    System.out.println("I'm taking $" + amount);
  }
}

@ApplicationScoped
public class Shop
{

  @Inject
  PaymentProcessor paymentProcessor;

  public void buyStuff()
  {
    paymentProcessor.processPayment(100);
  }
}

Chapter 8. JBoss EAP MBean Services

A managed bean, sometimes simply referred to as an MBean, is a type of JavaBean that is created with dependency injection. MBean services are the core building blocks of the JBoss EAP server.

8.1. Writing JBoss MBean Services

Writing a custom MBean service that relies on a JBoss service requires the service interface method pattern. A JBoss MBean service interface method pattern consists of a set of life cycle operations that inform an MBean service when it can create, start, stop, and destroy itself.

You can manage the dependency state using any of the following approaches:

  • If you want specific methods to be called on your MBean, declare those methods in your MBean interface. This approach allows your MBean implementation to avoid dependencies on JBoss specific classes.
  • If you are not bothered about dependencies on JBoss specific classes, then you may have your MBean interface extend the ServiceMBean interface and ServiceMBeanSupport class. The ServiceMBeanSupport class provides implementations of the service lifecycle methods like create, start, and stop. To handle a specific event like the start() event, you need to override startService() method provided by the ServiceMBeanSupport class.

8.1.1. A Standard MBean Example

This section develops two sample MBean services packaged together in a service archive (.sar).

ConfigServiceMBean interface declares specific methods like the start, getTimeout, and stop methods to start, hold, and stop the MBean correctly without using any JBoss specific classes. ConfigService class implements ConfigServiceMBean interface and consequently implements the methods used within that interface.

The PlainThread class extends the ServiceMBeanSupport class and implements the PlainThreadMBean interface. PlainThread starts a thread and uses ConfigServiceMBean.getTimeout() to determine how long the thread should sleep.

Sample MBean Services

package org.jboss.example.mbean.support;
public interface ConfigServiceMBean {
    int getTimeout();
    void start();
    void stop();
}
package org.jboss.example.mbean.support;
public class ConfigService implements ConfigServiceMBean {
    int timeout;
    @Override
    public int getTimeout() {
        return timeout;
    }
    @Override
    public void start() {
        //Create a random number between 3000 and 6000 milliseconds
        timeout = (int)Math.round(Math.random() * 3000) + 3000;
        System.out.println("Random timeout set to " + timeout + " seconds");
    }
    @Override
    public void stop() {
        timeout = 0;
    }
}

package org.jboss.example.mbean.support;
import org.jboss.system.ServiceMBean;
public interface PlainThreadMBean extends ServiceMBean {
    void setConfigService(ConfigServiceMBean configServiceMBean);
}

package org.jboss.example.mbean.support;
import org.jboss.system.ServiceMBeanSupport;
public class PlainThread extends ServiceMBeanSupport implements PlainThreadMBean {
    private ConfigServiceMBean configService;
    private Thread thread;
    private volatile boolean done;
    @Override
    public void setConfigService(ConfigServiceMBean configService) {
        this.configService = configService;
    }
    @Override
    protected void startService() throws Exception {
        System.out.println("Starting Plain Thread MBean");
        done = false;
        thread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    while (!done) {
                        System.out.println("Sleeping....");
                        Thread.sleep(configService.getTimeout());
                        System.out.println("Slept!");
                    }
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
        });
        thread.start();
    }
    @Override
    protected void stopService() throws Exception {
        System.out.println("Stopping Plain Thread MBean");
        done = true;
    }
}

The jboss-service.xml descriptor shows how the ConfigService class is injected into the PlainThread class using the inject tag. The inject tag establishes a dependency between PlainThreadMBean and ConfigServiceMBean, and thus allows PlainThreadMBean use ConfigServiceMBean easily.

JBoss-service.xml Service Descriptor

<server xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="urn:jboss:service:7.0 jboss-service_7_0.xsd"
        xmlns="urn:jboss:service:7.0">
 <mbean code="org.jboss.example.mbean.support.ConfigService" name="jboss.support:name=ConfigBean"/>
 <mbean code="org.jboss.example.mbean.support.PlainThread" name="jboss.support:name=ThreadBean">
  <attribute name="configService">
   <inject bean="jboss.support:name=ConfigBean"/>
  </attribute>
 </mbean>
</server>

After writing the sample MBeans you can package the classes and the jboss-service.xml descriptor in the META-INF folder of a service archive (.sar).

8.2. Deploying JBoss MBean Services

Deploy and test sample MBeans in managed domain

Use the following command to deploy the sample MBeans (ServiceMBeanTest.sar) in a managed domain:

deploy ~/Desktop/ServiceMBeanTest.sar --all-server-groups

Deploy and test sample MBeans on a standalone server

Use the following command to build and deploy the sample MBeans (ServiceMBeanTest.sar) on a standalone server:

deploy ~/Desktop/ServiceMBeanTest.sar

Undeploy sample MBeans

Use the following command to undeploy the sample MBeans:

undeploy ServiceMBeanTest.sar

Chapter 9. Concurrency Utilities

Concurrency Utilities is an API that accommodates Java SE concurrency utilities into the Java EE application environment specifications. It is defined in JSR 236: Concurrency Utilities for Java™ EE. JBoss EAP allows you to create, edit, and delete instances of EE concurrency utilities, thus making these instances readily available for applications to use.

Concurrency Utilities help to extend the invocation context by pulling in the existing context’s application threads and using these in its own threads. This extending of invocation context includes class loading, JNDI, and security contexts, by default.

Types of Concurrency Utilities include:

  • Context Service
  • Managed Thread Factory
  • Managed Executor Service
  • Managed Scheduled Executor Service

Concurrency Utilities in standalone.xml

<subsystem xmlns="urn:jboss:domain:ee:4.0">
            <spec-descriptor-property-replacement>false</spec-descriptor-property-replacement>
            <concurrent>
                <context-services>
                    <context-service name="default" jndi-name="java:jboss/ee/concurrency/context/default" use-transaction-setup-provider="true"/>
                </context-services>
                <managed-thread-factories>
                    <managed-thread-factory name="default" jndi-name="java:jboss/ee/concurrency/factory/default" context-service="default"/>
                </managed-thread-factories>
                <managed-executor-services>
                    <managed-executor-service name="default" jndi-name="java:jboss/ee/concurrency/executor/default" context-service="default" hung-task-threshold="60000" keepalive-time="5000"/>
                </managed-executor-services>
                <managed-scheduled-executor-services>
                    <managed-scheduled-executor-service name="default" jndi-name="java:jboss/ee/concurrency/scheduler/default" context-service="default" hung-task-threshold="60000" keepalive-time="3000"/>
                </managed-scheduled-executor-services>
            </concurrent>
            <default-bindings context-service="java:jboss/ee/concurrency/context/default" datasource="java:jboss/datasources/ExampleDS" managed-executor-service="java:jboss/ee/concurrency/executor/default" managed-scheduled-executor-service="java:jboss/ee/concurrency/scheduler/default" managed-thread-factory="java:jboss/ee/concurrency/factory/default"/>
</subsystem>

9.1. Context Service

Context service (javax.enterprise.concurrent.ContextService) allows you to build contextual proxies from existing objects. Contextual proxy prepares the invocation context, which is used by other concurrency utilities when the context is created or invoked, before transferring the invocation to the original object.

Attributes of context service concurrency utility include:

  • name: A unique name within all the context services.
  • jndi-name: Defines where the context service should be placed in the JNDI.
  • use-transaction-setup-provider: Optional. Indicates if the contextual proxies built by the context service should suspend transactions in context, when invoking the proxy objects. Its value defaults to false, but the default context-service has the value true.

See the example above for the usage of context service concurrency utility.

Add a new context service

/subsystem=ee/context-service=newContextService:add(jndi-name=java:jboss/ee/concurrency/contextservice/newContextService)

Change a context service

/subsystem=ee/context-service=newContextService:write-attribute(name=jndi-name, value=java:jboss/ee/concurrency/contextservice/changedContextService)

This operation requires reload.

Remove a context service

/subsystem=ee/context-service=newContextService:remove()

This operation requires reload.

9.2. Managed Thread Factory

The managed thread factory (javax.enterprise.concurrent.ManagedThreadFactory) concurrency utility allows Java EE applications to create Java threads. JBoss EAP handles the managed thread factory instances, hence Java EE applications cannot invoke any lifecycle related method.

Attributes of managed thread factory concurrency utility include:

  • context-service: A unique name within all managed thread factories.
  • jndi-name: Defines where in the JNDI the managed thread factory should be placed.
  • priority: Optional. Indicates the priority for new threads created by the factory, and defaults to 5.

Add a new managed thread factory

/subsystem=ee/managed-thread-factory=newManagedTF:add(context-service=newContextService, jndi-name=java:jboss/ee/concurrency/threadfactory/newManagedTF, priority=2)

Change a managed thread factory

/subsystem=ee/managed-thread-factory=newManagedTF:write-attribute(name=jndi-name, value=java:jboss/ee/concurrency/threadfactory/changedManagedTF)

This operation requires reload. Similarly, you can change other attributes as well.

Remove a managed thread factory

/subsystem=ee/managed-thread-factory=newManagedTF:remove()

This operation requires reload.

9.3. Managed Executor Service

Managed executor service (javax.enterprise.concurrent.ManagedExecutorService) allows Java EE applications to submit tasks for asynchronous execution. JBoss EAP handles managed executor service instances, hence Java EE applications cannot invoke any lifecycle related method.

Attributes of managed executor service concurrency utility include:

  • context-service: Optional. References an existing context service by its name. If specified, then the referenced context service will capture the invocation context present when submitting a task to the executor, which will then be used when executing the task.
  • jndi-name: Defines where the managed thread factory should be placed in the JNDI.
  • max-threads: Defines the maximum number of threads used by the executor, which defaults to Integer.MAX_VALUE.
  • thread-factory: References an existing managed thread factory by its name, to handle the creation of internal threads. If not specified, then a managed thread factory with default configuration will be created and used internally.
  • core-threads: Provides the number of threads to keep in the executor’s pool, even if they are idle. A value of 0 means there is no limit.
  • keepalive-time: Defines the time, in milliseconds, that an internal thread may be idle. The attribute default value is 60000.
  • queue-length: Indicates the number of tasks that can be stored in the input queue. The default value is 0, which means the queue capacity is unlimited.
  • hung-task-threshold: Defines the time, in milliseconds, after which tasks are considered hung by the managed executor service and forcefully aborted. If the value is 0 (which is the default), tasks are never considered hung.
  • long-running-tasks: Suggests optimizing the execution of long running tasks, and defaults to false.
  • reject-policy: Defines the policy to use when a task is rejected by the executor. The attribute value may be the default ABORT, which means an exception should be thrown, or RETRY_ABORT, which means the executor will try to submit it once more, before throwing an exception

Add a new managed executor service

/subsystem=ee/managed-executor-service=newManagedExecutorService:add(jndi-name=java:jboss/ee/concurrency/executor/newManagedExecutorService, core-threads=7, thread-factory=default)

Change a managed executor service

/subsystem=ee/managed-executor-service=newManagedExecutorService:write-attribute(name=core-threads,value=10)

This operation requires reload. Similarly, you can change other attributes too.

Remove a managed executor service

/subsystem=ee/managed-executor-service=newManagedExecutorService:remove()

This operation requires reload.

9.4. Managed Scheduled Executor Service

Managed scheduled executor service (javax.enterprise.concurrent.ManagedScheduledExecutorService) allows Java EE applications to schedule tasks for asynchronous execution. JBoss EAP handles managed scheduled executor service instances, hence Java EE applications cannot invoke any lifecycle related method.

Attributes of managed executor service concurrency utility include:

  • context-service: References an existing context service by its name. If specified then the referenced context service will capture the invocation context present when submitting a task to the executor, which will then be used when executing the task.
  • hung-task-threshold: Defines the time, in milliseconds, after which tasks are considered hung by the managed scheduled executor service and forcefully aborted. If the value is 0 (which is the default), tasks are never considered hung.
  • keepalive-time: Defines the time, in milliseconds, that an internal thread may be idle. The attribute default value is 60000.
  • reject-policy: Defines the policy to use when a task is rejected by the executor. The attribute value may be the default ABORT, which means an exception should be thrown, or RETRY_ABORT, which means the executor will try to submit it once more, before throwing an exception.
  • core-threads: Provides the number of threads to keep in the executor’s pool, even if they are idle. A value of 0 means there is no limit.
  • jndi-name: Defines where the managed scheduled executor service should be placed in the JNDI .
  • long-running-tasks: Suggests optimizing the execution of long running tasks, and defaults to false.
  • thread-factory: References an existing managed thread factory by its name, to handle the creation of internal threads. If not specified, then a managed thread factory with default configuration will be created and used internally.

Add a new managed scheduled executor service

/subsystem=ee/managed-scheduled-executor-service=newManagedScheduledExecutorService:add(jndi-name=java:jboss/ee/concurrency/scheduledexecutor/newManagedScheduledExecutorService, core-threads=7, context-service=default)

This operation requires reload.

Changed a managed scheduled executor service

/subsystem=ee/managed-scheduled-executor-service=newManagedScheduledExecutorService:write-attribute(name=core-threads, value=10)

This operation requires reload. Similarly, you can change other attributes.

Remove a managed scheduled executor service

/subsystem=ee/managed-scheduled-executor-service=newManagedScheduledExecutorService:remove()

This operation requires reload.

Chapter 10. Undertow

10.1. Introduction to Undertow Handler

Undertow is a web server designed to be used for both blocking and non-blocking tasks. It replaces JBoss Web in JBoss EAP 7. Some of its main features are:

  • High Performance
  • Embeddable
  • Servlet 3.1
  • Web Sockets
  • Reverse Proxy

Request Lifecycle

When a client connects to the server, Undertow creates a io.undertow.server.HttpServerConnection. When the client sends a request, it is parsed by the Undertow parser, and then the resulting io.undertow.server.HttpServerExchange is passed to the root handler. When the root handler finishes, one of four things can happen:

The exchange is completed
And exchange is considered complete if both request and response channels have been fully read or written. For requests with no content, such as GET and HEAD, the request side is automatically considered fully read. The read side is considered complete when a handler has written out the full response and has closed and fully flushed the response channel. If an exchange is already complete, then no action is taken.
The root handler returns normally without completing the exchange
In this case the exchange is completed by calling HttpServerExchange.endExchange().
The root handler returns with an Exception
In this case a response code of 500 is set and the exchange is ended using HttpServerExchange.endExchange().
The root handler can return after HttpServerExchange.dispatch() has been called, or after async IO has been started
In this case the dispatched task will be submitted to the dispatch executor, or if async IO has been started on either the request or response channels then this will be started. In this case the exchange will not be finished. It is up to your async task to finish the exchange when it is done processing.

By far the most common use of HttpServerExchange.dispatch() is to move execution from an IO thread where blocking is not allowed into a worker thread, which does allow for blocking operations. This pattern generally looks like:

Dispatching to a worker thread:

public void handleRequest(final HttpServerExchange exchange) throws Exception {
    if (exchange.isInIoThread()) {
      exchange.dispatch(this);
      return;
    }
    //handler code
}

Because exchange is not actually dispatched until the call stack returns, you can be sure that more that one thread is never active in an exchange at once. The exchange is not thread safe. However it can be passed between multiple threads as long as both threads do not attempt to modify it at once.

Ending the Exchange

There are two ways to end an exchange, either by fully reading the request channel, and calling shutdownWrites() on the response channel and then flushing it, or by calling HttpServerExchange.endExchange(). When endExchange() is called, Undertow will check if the content has been generated yet. If it has, then it will simply drain the request channel and close and flush the response channel. If not and there are any default response listeners registered on the exchange, then Undertow will give each of them a chance to generate a default response. This mechanism is how default error pages are generated.

For more information on configuring the Undertow, see Configuring the Web Server in the JBoss EAP Configuration Guide.

10.2. Using Existing Undertow Handlers with a Deployment

Undertow provides a default set of handlers that you can use with any application deployed to JBoss EAP. You can find a full list of the available handlers as well as their attributes here.

To use a handler with a deployment, you need to add a WEB-INF/undertow-handlers.conf file.

Example WEB-INF/undertow-handlers.conf

allowed-methods(methods='GET')

All handlers may also take an optional predicate to apply that handler in specific cases.

Example WEB-INF/undertow-handlers.conf with Optional Predicate

path('/my-path') -> allowed-methods(methods='GET')

The above example will only apply the allowed-methods handler to the path /my-path.

Some handlers have a default parameter, which allows you to specify the value of that parameter in the handler definition without using the name.

Example WEB-INF/undertow-handlers.conf Using the Default Parameter

path('/a') -> redirect('/b')

You also may update the WEB-INF/jboss-web.xml file to include the definition of one or more handlers but using WEB-INF/undertow-handlers.conf is preferred.

Example WEB-INF/jboss-web.xml

<jboss-web>
    <http-handler>
        <class-name>io.undertow.server.handlers.AllowedMethodsHandler</class-name>
        <param>
            <param-name>methods</param-name>
            <param-value>GET</param-value>
        </param>
    </http-handler>
</jboss-web>

A full list of provided Undertow handlers can be found here.

10.3. Creating Custom Handlers

  • A custom handler can be defined in the WEB-INF/jboss-web.xml file.
<jboss-web>
    <http-handler>
        <class-name>org.jboss.example.MyHttpHandler</class-name>
    </http-handler>
</jboss-web>

Example of a handler class:

package org.jboss.example;

import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;

public class MyHttpHandler implements HttpHandler {
    private HttpHandler next;

    public MyHttpHandler(HttpHandler next) {
        this.next = next;
    }

    public void handleRequest(HttpServerExchange exchange) throws Exception {
        // do something
        next.handleRequest(exchange);
    }
}

  • Parameters could also be set for the custom handler via the WEB-INF/jboss-web.xml file.
<jboss-web>
    <http-handler>
        <class-name>org.jboss.example.MyHttpHandler</class-name>
        <param>
            <param-name>myParam</param-name>
            <param-value>foobar</param-value>
        </param>
    </http-handler>
</jboss-web>

For these parameters to work, the handler class needs to have corresponding setters.

package org.jboss.example;

import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;

public class MyHttpHandler implements HttpHandler {
    private HttpHandler next;
    private String myParam;

    public MyHttpHandler(HttpHandler next) {
        this.next = next;
    }

    public void setMyParam(String myParam) {
        this.myParam = myParam;
    }

    public void handleRequest(HttpServerExchange exchange) throws Exception {
        // do something, use myParam
        next.handleRequest(exchange);
    }
}
  • Instead of using the WEB-INF/jboss-web.xml for defining the handler, it could also be defined in the WEB-INF/undertow-handlers.conf file.

    myHttpHandler(myParam='foobar')

    For the handler defined in WEB-INF/undertow-handlers.conf to work, two things need to be created:

    1. An implementation of HandlerBuilder, which defines the corresponding syntax bits for undertow-handlers.conf and is responsible for creating the HttpHandler, wrapped in a HandlerWrapper.

      package org.jboss.example;
      
      import io.undertow.server.HandlerWrapper;
      import io.undertow.server.HttpHandler;
      import io.undertow.server.handlers.builder.HandlerBuilder;
      
      import java.util.Collections;
      import java.util.Map;
      import java.util.Set;
      
      public class MyHandlerBuilder implements HandlerBuilder {
          public String name() {
              return "myHttpHandler";
          }
      
          public Map<String, Class<?>> parameters() {
              return Collections.<String, Class<?>>singletonMap("myParam", String.class);
          }
      
          public Set<String> requiredParameters() {
              return Collections.emptySet();
      
          }
      
          public String defaultParameter() {
              return null;
      
          }
      
          public HandlerWrapper build(final Map<String, Object> config) {
              return new HandlerWrapper() {
                  public HttpHandler wrap(HttpHandler handler) {
                      MyHttpHandler result = new MyHttpHandler(handler);
                      result.setMyParam((String) config.get("myParam"));
                      return result;
                  }
              };
          }
      }
    2. An entry in the file META-INF/services/io.undertow.server.handlers.builder.HandlerBuilder. This file must be on the class path, for example, in WEB-INF/classes.

      org.jboss.example.MyHandlerBuilder

Chapter 11. Java Transaction API (JTA)

11.1. Overview

11.1.1. Overview of Java Transactions API (JTA)

Introduction

These topics provide a foundational understanding of the Java Transactions API (JTA).

11.2. Transaction Concepts

11.2.1. About Transactions

A transaction consists of two or more actions which must either all succeed or all fail. A successful outcome is a commit, and a failed outcome is a roll-back. In a roll-back, each member’s state is reverted to its state before the transaction attempted to commit.

The typical standard for a well-designed transaction is that it is Atomic, Consistent, Isolated, and Durable (ACID).

11.2.2. About ACID Properties for Transactions

ACID is an acronym which stands for Atomicity, Consistency, Isolation, and Durability. This terminology is usually used in the context of databases or transactional operations.

Atomicity
For a transaction to be atomic, all transaction members must make the same decision. Either they all commit, or they all roll back. If atomicity is broken, what results is termed a heuristic outcome.
Consistency
Consistency means that data written to the database is guaranteed to be valid data, in terms of the database schema. The database or other data source must always be in a consistent state. One example of an inconsistent state would be a field in which half of the data is written before an operation aborts. A consistent state would be if all the data were written, or the write were rolled back when it could not be completed.
Isolation
Isolation means that data being operated on by a transaction must be locked before modification, to prevent processes outside the scope of the transaction from modifying the data.
Durability
Durability means that in the event of an external failure after transaction members have been instructed to commit, all members will be able to continue committing the transaction when the failure is resolved. This failure may be related to hardware, software, network, or any other involved system.

11.2.3. About the Transaction Coordinator or Transaction Manager

The terms Transaction Coordinator and Transaction Manager (TM) are mostly interchangeable in terms of transactions with JBoss EAP. The term Transaction Coordinator is usually used in the context of distributed JTS transactions.

In JTA transactions, the TM runs within JBoss EAP and communicates with transaction participants during the two-phase commit protocol.

The TM tells transaction participants whether to commit or roll back their data, depending on the outcome of other transaction participants. In this way, it ensures that transactions adhere to the ACID standard.

11.2.4. About Transaction Participants

A transaction participant is any resource within a transaction, which has the ability to commit or roll back state. It is generally a database or a JMS broker, but by implementing the transaction interface, a user code could also act as a transaction participant. Each participant of a transaction independently decides whether it is able to commit or roll back its state, and only if all participants can commit, does the transaction as a whole succeed. Otherwise, each participant rolls back its state, and the transaction as a whole fails. The TM coordinates the commit or rollback operations and determines the outcome of the transaction.

11.2.5. About Java Transactions API (JTA)

Java Transactions API (JTA) is part of Java Enterprise Edition specification. It is defined in JSR-907.

Implementation of JTA is done using TM, which is covered by project Narayana for JBoss EAP application server. TM allows application to assign various resources, for example, database or JMS brokers, through a single global transaction. The global transaction is referred as XA transaction. Generally resources with XA capabilities are included in such transaction, but non-XA resources could also be part of global transaction. There are several optimizations which help non-XA resources to behave as XA capable resources. For more information, refer LRCO Optimization for Single-phase Commit

In this document, the term JTA refers to two things:

  1. Java Transaction API, which is defined by Java EE specification
  2. Indicates how the TM processes the transactions.

    TM works in JTA transactions mode, the data is shared via memory and transaction context is transferred by remote EJB calls. In JTS mode, the data is shared by sending Common Object Request Broker Architecture (CORBA) messages and transaction context is transferred by IIOP calls. Both modes support distribution of transaction over multiple JBoss EAP servers.

11.2.6. About Java Transaction Service (JTS)

Java Transaction Service (JTS) is a mapping of the Object Transaction Service (OTS) to Java. Java EE applications use the JTA API to manage transactions. JTA API then interacts with a JTS transaction implementation when the transaction manager is switched to JTS mode. JTS works over the IIOP protocol. Transaction managers that use JTS communicate with each other using a process called an Object Request Broker (ORB), using a communication standard called Common Object Request Broker Architecture (CORBA). For more information, see ORB Configuration in the JBoss EAP Configuration Guide.

Using JTA API from an application standpoint, a JTS transaction behaves in the same way as a JTA transaction.

Note

The implementation of JTS included in JBoss EAP supports distributed transactions. The difference from fully-compliant JTS transactions is interoperability with external third-party ORBs. This feature is unsupported with JBoss EAP. Supported configurations distribute transactions across multiple JBoss EAP containers only.

11.2.7. About XA Resources and XA Transactions

XA stands for eXtended Architecture, which was developed by the X/Open Group to define a transaction that uses more than one back-end data store. The XA standard describes the interface between a global TM and a local resource manager. XA allows multiple resources, such as application servers, databases, caches, and message queues, to participate in the same transaction, while preserving all four ACID properties. One of the four ACID properties is atomicity, which means that if one of the participants fails to commit its changes, the other participants abort the transaction, and restore their state to the same status as before the transaction occurred. An XA resource is a resource that can participate in an XA global transaction.

An XA transaction is a transaction which can span multiple resources. It involves a coordinating TM, with one or more databases or other transactional resources, all involved in a single global XA transaction.

11.2.8. About XA Recovery

TM implements X/Open XA specification and supports XA transactions across multiple XA resources.

XA Recovery is the process of ensuring that all resources affected by a transaction are updated or rolled back, even if any of the resources, which are transaction participants, crash or become unavailable. Within the scope of JBoss EAP, the transactions subsystem provides the mechanisms for XA Recovery to any XA resources or subsystems which use them, such as XA datasources, JMS message queues, and JCA resource adapters.

XA Recovery happens without user intervention. In the event of an XA Recovery failure, errors are recorded in the log output. Contact Red Hat Global Support Services if you need assistance. The XA recovery process is driven by periodic recovery thread which is launched by default each 2 minutes. The periodic recovery thread processes all unfinished transactions.

Note

It can take four to eight minutes to complete the recovery for an in-doubt transaction because it might require multiple runs of the recovery process.

11.2.9. Limitations of the XA Recovery Process

XA recovery has the following limitations:

The transaction log may not be cleared from a successfully committed transaction

If the JBoss EAP server crashes after an XAResource commit method successfully completes and commits the transaction, but before the coordinator can update the log, you may see the following warning message in the log when you restart the server:

ARJUNA016037: Could not find new XAResource to use for recovering non-serializable XAResource XAResourceRecord

This is because upon recovery, the JBoss Transaction Manager (TM) sees the transaction participants in the log and attempts to retry the commit. Eventually the JBoss TM assumes the resources are committed and no longer retries the commit. In this situation, can safely ignore this warning as the transaction is committed and there is no loss of data.

To prevent the warning, set the com.arjuna.ats.jta.xaAssumeRecoveryComplete property value to true . This property is checked whenever a new XAResource instance cannot be located from any registered XAResourceRecovery instance. When set to true, the recovery assumes that a previous commit attempt succeeded and the instance can be removed from the log with no further recovery attempts. This property must be used with care because it is global and when used incorrectly could result in XAResource instances remaining in an uncommitted state.

Note

JBoss EAP 7.0 has an implemented enhancement to clear transaction logs after a successfully committed transaction and the above situation should not occur frequently.

Rollback is not called for JTS transaction when a server crashes at the end of XAResource.prepare()
If the JBoss EAP server crashes after the completion of an XAResource prepare() method call, all of the participating XAResources are locked in the prepared state and remain that way upon server restart. The transaction is not rolled back and the resources remain locked until the transaction times out or a DBA manually rolls back the resources and clears the transaction log. For more information, see https://issues.jboss.org/browse/JBTM-2124
Periodic recovery can occur on committed transactions.

When the server is under excessive load, the server log may contain the following warning message, followed by a stacktrace:

ARJUNA016027: Local XARecoveryModule.xaRecovery got XA exception XAException.XAER_NOTA: javax.transaction.xa.XAException

Under heavy load, the processing time taken by a transaction can overlap with the timing of the periodic recovery process’s activity. The periodic recovery process detects the transaction still in progress and attempts to initiate a rollback but in fact the transaction continues to completion. At the time the periodic recovery attempts but fails the rollback, it records the rollback failure in the server log. The underlying cause of this issue will be addressed in a future release, but in the meantime a workaround is available.

Increase the interval between the two phases of the recovery process by setting the com.arjuna.ats.jta.orphanSafetyInterval property to a value higher than the default value of 10000 milliseconds. A value of 40000 milliseconds is recommended. Please note that this does not solve the issue, instead it decreases the probability that it will occur and that the warning message will be shown in the log. For more information, see https://developer.jboss.org/thread/266729

11.2.10. About the 2-Phase Commit Protocol

The two-phase commit (2PC) protocol refers to an algorithm to determine the outcome of a transaction. 2PC is driven by the Transaction Manager (TM) as a process of finishing XA transactions.

Phase 1: Prepare

In the first phase, the transaction participants notify the transaction coordinator whether they are able to commit the transaction or must roll back.

Phase 2: Commit

In the second phase, the transaction coordinator makes the decision about whether the overall transaction should commit or roll back. If any one of the participants cannot commit, the transaction must roll back. Otherwise, the transaction can commit. The coordinator directs the resources about what to do, and they notify the coordinator when they have done it. At that point, the transaction is finished.

11.2.11. About Transaction Timeouts

In order to preserve atomicity and adhere to the ACID standard for transactions, some parts of a transaction can be long-running. Transaction participants need to lock an XA resource, that is part of database table or message in a queue, when they commit. The TM needs to wait to hear back from each transaction participant before it can direct them all whether to commit or roll back. Hardware or network failures can cause resources to be locked indefinitely.

Transaction timeouts can be associated with transactions in order to control their lifecycle. If a timeout threshold passes before the transaction commits or rolls back, the timeout causes the transaction to be rolled back automatically.

You can configure default timeout values for the entire transaction subsystem, or you disable default timeout values, and specify timeouts on a per-transaction basis.

11.2.12. About Distributed Transactions

A distributed transaction, is a transaction with participants on multiple JBoss EAP servers. Java Transaction Service (JTS) specification mandates that JTS transactions be able to be distributed across application servers from different vendors. Java Transaction API (JTA) does not define that but JBoss EAP supports distributed JTA transactions among JBoss EAP servers.

Note

Transaction distribution among servers from different vendors is not supported.

Note

In other application server vendor documentation, you can find that term distributed transaction means XA transaction. In context of JBoss EAP documentation, the distributed transaction refers transactions distributed among several JBoss EAP application servers. Transaction which consists from different resources (for example, database resource and jms resource) are referred as XA transactions in this document. For more information, refer to About Java Transaction Service (JTS) and About XA Datasources and XA Transactions.

11.2.13. About the ORB Portability API

The Object Request Broker (ORB) is a process which sends and receives messages to transaction participants, coordinators, resources, and other services distributed across multiple application servers. An ORB uses a standardized Interface Description Language (IDL) to communicate and interpret messages. Common Object Request Broker Architecture (CORBA) is the IDL used by the ORB in JBoss EAP.

The main type of service which uses an ORB is a system of distributed Java Transactions, using the Java Transaction Service (JTS) specification. Other systems, especially legacy systems, may choose to use an ORB for communication, rather than other mechanisms such as remote Enterprise JavaBeans or JAX-WS or JAX-RS web services.

The ORB Portability API provides mechanisms to interact with an ORB. This API provides methods for obtaining a reference to the ORB, as well as placing an application into a mode where it listens for incoming connections from an ORB. Some of the methods in the API are not supported by all ORBs. In those cases, an exception is thrown.

The API consists of two different classes:

  • com.arjuna.orbportability.orb
  • com.arjuna.orbportability.oa

Refer to the JBoss EAP Javadocs bundle from the Red Hat Customer Portal for specific details about the methods and properties included in the ORB Portability API.

11.3. Transaction Optimizations

11.3.1. Overview of Transaction Optimizations

The Transaction Manager (TM) of JBoss EAP includes several optimizations that your application can take advantage of.

Optimizations serve to enhance the 2-phase commit protocol in particular cases. Generally, the TM starts a global transaction which passes through the 2-phase commit. But when we optimize these transactions, in certain cases, the TM does not need to proceed with full 2-phased commits and thus the process gets faster.

Different optimizations used by the TM are described in detail below.

11.3.2. About the LRCO Optimization for Single-phase Commit (1PC)

Single-phase Commit (1PC)

Although the 2-phase commit protocol (2PC) is more commonly encountered with transactions, some situations do not require, or cannot accommodate, both phases. In these cases, you can use the single phase commit (1PC) protocol. The single phase commnit protocol is used when only one XA or non-XA resource is a part of the global transaction.

The prepare phase generally locks the resource until the second phase is processed. Single-phase commit means that the prepare phase is skipped and only the commit is processed on the resource. If not specified, the single-phase commit optimization is used automatically when the global transaction contains only one participant.

Last Resource Commit Optimization (LRCO)

In situations where non-XA datasource participate in XA transaction, an optimization known as the Last Resource Commit Optimization (LRCO) is employed. While this protocol allows for most transactions to complete normally, certain types of error can cause an inconsistent transaction outcome. Therefore, use this approach only as a last resort.

The non-XA resource is processed at the end of the prepare phase, and an attempt is made to commit it. If the commit succeeds, the transaction log is written and the remaining resources go through the commit phase. If the last resource fails to commit, the transaction is rolled back.

Where a single local TX datasource is used in a transaction, the LRCO is automatically applied to it.

Previously, adding non-XA resources to an XA transaction was achieved via the LRCO method. However, there is a window of failure in LRCO. The procedure for adding non-XA resources to an XA transaction via the LRCO method is as follows:

  1. Prepare XA transaction
  2. Commit LRCO
  3. Write tx log
  4. Commit XA transaction

If the procedure crashes between steps 2 and step 3, this could lead to data inconsistency and you cannot commit the XA transaction. The data inconsistency is because the LRCO non-XA resource is committed but information about preparation of XA resource was not recorded. The recovery manager will rollback the resource after the server is up. CMR eliminates this restriction and allows non-XA to be reliably enlisted in an XA transaction.

Note

CMR is a special case of LRCO optimalization, which could be used only for datasources. It is not suitable for all non-XA resources.

11.3.2.1. Commit Markable Resource

Summary

Configuring access to a resource manager using the Commit Markable Resource (CMR) interface ensures that a non-XA datasource can be reliably enlisted to an XA (2PC) transaction. It is an implementation of the LRCO algorithm, which makes non-XA resource fully recoverable.

To configure CMR, you must:

  1. Create tables in database.
  2. Enable datasource to be connectable.
  3. Add reference to transactions subsystem.
Create Tables in Database

A transaction may contain only one CMR resource. You must have a table created for which the following SQL would work.

SELECT xid,actionuid FROM _tableName_ WHERE transactionManagerID IN (String[])
DELETE FROM _tableName_ WHERE xid IN (byte[[]])
INSERT INTO _tableName_ (xid, transactionManagerID, actionuid) VALUES (byte[],String,byte[])

Some examples of the SQL query

Sybase:

CREATE TABLE xids (xid varbinary(144), transactionManagerID varchar(64), actionuid varbinary(28))

Oracle:

CREATE TABLE xids (xid RAW(144), transactionManagerID varchar(64), actionuid RAW(28))
CREATE UNIQUE INDEX index_xid ON xids (xid)

IBM:

CREATE TABLE xids (xid VARCHAR(255) for bit data not null, transactionManagerID
varchar(64), actionuid VARCHAR(255) for bit data not null)
CREATE UNIQUE INDEX index_xid ON xids (xid)

SQL Server:

CREATE TABLE xids (xid varbinary(144), transactionManagerID varchar(64), actionuid varbinary(28))
CREATE UNIQUE INDEX index_xid ON xids (xid)

Postgres:

CREATE TABLE xids (xid bytea, transactionManagerID varchar(64), actionuid bytea)
CREATE UNIQUE INDEX index_xid ON xids (xid)

MariaDB:

CREATE TABLE xids (xid BINARY(144), transactionManagerID varchar(64), actionuid BINARY(28))
CREATE UNIQUE INDEX index_xid ON xids (xid)

MySQL:

CREATE TABLE xids (xid VARCHAR(255), transactionManagerID varchar(64), actionuid VARCHAR(255))
CREATE UNIQUE INDEX index_xid ON xids (xid)
Enabling Datasource to be Connectable

By default, the CMR feature is disabled for datasources. To enable it, you must create or modify the datasource configuration and ensure that the connectible attribute is set to true. The following is an example of the datasources section of a server XML configuration file:

<datasource enabled="true" jndi-name="java:jboss/datasources/ConnectableDS" pool-name="ConnectableDS" jta="true" use-java-context="true" connectable="true"/>
Note

This feature is not applicable to XA datasources.

You can also enable a resource manager as a CMR, using the management CLI, as follows:

/subsystem=datasources/data-source=ConnectableDS:add(enabled="true", jndi-name="java:jboss/datasources/ConnectableDS", jta="true", use-java-context="true", connectable="true", connection-url="validConnectionURL", exception-sorter="org.jboss.jca.adapters.jdbc.extensions.mssql.MSSQLExceptionSorter", driver-name="h2")
Updating an Existing Resource to Use the New CMR Feature

If you only need to update an existing datasource to use the CMR feature, then simply modify the connectable attribute:

/subsystem=datasources/data-source=ConnectableDS:write-attribute(name=connectable,value=true)
Add Reference to Transactions Subsystem

The transactions subsystem identifies the datasources that are CMR capable through an entry to the transactions subsystem config section as shown below:

<subsystem xmlns="urn:jboss:domain:transactions:3.0">
    ...
    <commit-markable-resources>
        <commit-markable-resource jndi-name="java:jboss/datasources/ConnectableDS">
            <xid-location name="xids" batch-size="100" immediate-cleanup="false"/>
        </commit-markable-resource>
        ...
    </commit-markable-resources>
</subsystem>
Note

You must restart the server after adding the CMR reference under the transactions subsystem.

Note

Use the exception-sorter parameter in the datasource configuration. For details, see Example Datasource Configurations in the JBoss EAP Configuration Guide.

11.3.3. About the Presumed-Abort Optimization

If a transaction is going to roll back, it can record this information locally and notify all enlisted participants. This notification is only a courtesy, and has no effect on the transaction outcome. After all participants have been contacted, the information about the transaction can be removed.

If a subsequent request for the status of the transaction occurs there will be no information available. In this case, the requester assumes that the transaction has aborted and rolled back. This presumed-abort optimization means that no information about participants needs to be made persistent until the transaction has decided to commit, since any failure prior to this point will be assumed to be an abort of the transaction.

11.3.4. About the Read-Only Optimization

When a participant is asked to prepare, it can indicate to the coordinator that it has not modified any data during the transaction. Such a participant does not need to be informed about the outcome of the transaction, since the fate of the participant has no affect on the transaction. This read-only participant can be omitted from the second phase of the commit protocol.

11.4. Transaction Outcomes

11.4.1. About Transaction Outcomes

There are three possible outcomes for a transaction.

Commit
If every transaction participant can commit, the transaction coordinator directs them to do so. See About Transaction Commit for more information.
Roll-back
If any transaction participant cannot commit, or the transaction coordinator cannot direct participants to commit, the transaction is rolled back. See About Transaction Roll-Back for more information.
Heuristic outcome
If some transaction participants commit and others roll back. it is termed a heuristic outcome. Heuristic outcomes require human intervention. See About Heuristic Outcomes for more information.

11.4.2. About Transaction Commit

When a transaction participant commits, it makes its new state durable. The new state is created by the participant doing the work involved in the transaction. The most common example is when a transaction member writes records to a database.

After commit, information about the transaction is removed from the transaction coordinator, and the newly-written state is now the durable state.

11.4.3. About Transaction Roll-Back

A transaction participant rolls back by restoring its state to reflect the state before the transaction began. After a roll-back, the state is the same as if the transaction had never been started.

11.4.4. About Heuristic Outcomes

A heuristic outcome, or non-atomic outcome, is a situation where the decisions of the participants in a transaction differ from that of the transaction manager. Heuristic outcomes can cause loss of integrity to the system, and usually requires human intervention to resolve. Do not write code which relies on them.

Heuristic outcomes typically occur during the second phase of the 2-phase commit (2PC) protocol. In rare cases, this outcome may occur in 1PC. They are often caused by failures to the underlying hardware or communications subsystems of the underlying servers.

Heuristic is possible due to timeouts in various subsystems or resources even with transaction manager and full crash recovery. In any system that requires some form of distributed agreement, situations may arise some parts of the system diverge in terms of the global outcome.

There are four different types of heuristic outcomes:

Heuristic rollback

The commit operation was not able to commit the resources but all of the participants were able to be rolled back and so an atomic outcome was still achieved.

Heuristic commit

An attempted rollback operation failed because all of the participants unilaterally committed. This may happen if, for example, the coordinator is able to successfully prepare the transaction but then decides to roll it back because of a failure on its side, such as a failure to update its log. In the interim, the participants may decide to commit.

Heuristic mixed

Some participants committed and others rolled back.

Heuristic hazard

The disposition of some of the updates is unknown. For those which are known, they have either all been committed or all rolled back.

11.4.5. JBoss Transactions Errors and Exceptions

For details about exceptions thrown by methods of the UserTransaction class, see the UserTransaction API specification at http://docs.oracle.com/javaee/7/api/javax/transaction/UserTransaction.html.

11.5. Overview of the Transaction Lifecycle

11.5.1. Transaction Lifecycle

See About Java Transactions API (JTA) for more information on Java Transactions API (JTA).

When a resource asks to participate in a transaction, a chain of events is set in motion. The Transaction Manager (TM) is a process that lives within the application server and manages transactions. Transaction participants are objects which participate in a transaction. Resources are datasources, JMS connection factories, or other JCA connections.

  1. Your application starts a new transaction

    To begin a transaction, your application obtains an instance of class UserTransaction from JNDI or, if it is an EJB, from an annotation. The UserTransaction interface includes methods for beginning, committing, and rolling back top-level transactions. Newly-created transactions are automatically associated with their invoking thread. Nested transactions are not supported in JTA, so all transactions are top-level transactions.

    An EJB starts a transaction when the UserTransaction.begin() method is called. The default behavior of this transaction could be affected by use of the TransactionAttribute annotation or the ejb.xml descriptor. Any resource that is used after that point is associated with the transaction. If more than one resource is enlisted, your transaction becomes an XA transaction, and participates in the two-phase commit protocol at commit time.

    Note

    By default, transactions are driven by application containers in EJB. This is called Container Managed Transaction (CMT). To make the transaction user driven, you will need to change the Transaction Management to Bean Managed Transaction (BMT). In BMT, the UserTransaction object is available for user to manage the transaction.

  2. Your application modifies its state

    In the next step, your application performs its work and makes changes to its state, only on enlisted resources.

  3. Your application decides to commit or roll back

    When your application has finished changing its state, it decides whether to commit or roll back. It calls the appropriate method, either UserTransaction.commit() or UserTransaction.rollback(). For a CMT, this process is driven automatically, whereas for a BMT, a method commit or rollback of the UserTransaction has to be explicitly called.

  4. TM removes the transaction from its records

    After the commit or rollback completes, the TM cleans up its records and removes information about your transaction from the transaction log.

Failure Recovery

If a resource, transaction participant, or the application server crashes or become unavailable, the Transaction Manager handles recovery when the underlying failure is resolved and the resource is available again. This process happens automatically. For more information, see XA Recovery.

11.6. Transaction Subsystem Configuration

11.6.1. Transactions Configuration Overview

Introduction

The transactions subsystem allows you to configure Transaction Manager (TM) options such as statistics, timeout values, and transaction logging.

For details, see Transactions Subsystem Configuration in the JBoss EAP Configuration Guide.

11.6.2. Configuring the Transaction Manager

You can configure the transaction manager using the web-based management console or the command line management CLI.

Configuring the Transaction Manager Using the Management Console

The following steps explain how to configure the transaction manager using the web-based management console:

  1. Select the Configuration tab from the top of the screen.
  2. If you are running JBoss EAP as a managed domain, choose the desired profile to modify.
  3. From the Subsystem list, select Transactions and click View.
  4. Click Edit on the appropriate tab for the settings that you want to edit, such as Recovery for recovery options.
  5. Make the necessary changes and click Save to save the changes.
  6. Click Need Help? to display help text.
Configuring the Transaction Manager Using the Management CLI

Using the management CLI, you can configure the transaction manager using a series of commands. The commands all begin with /subsystem=transactions for a standalone server or /profile=default/subsystem=transactions/ for the default profile in a managed domain.

For a detailed listing of all the transaction manager configuration options, see the Transaction Manager Configuration Options for JBoss EAP.

11.6.3. Transaction Logging

11.6.3.1. About Transaction Log Messages

You can track the transaction status while keeping the log files readable by using the DEBUG log level for the transaction logger. For detailed debugging, use the TRACE log level. Refer to Configuring Logging for the Transactions Subsystem for information on configuring the transaction logger.

Transaction Manager (TM) can generate a lot of logging information when configured to log in the TRACE log level. Following are some of the most commonly-seen messages. This list is not comprehensive, so you may see messages other than these.

Table 11.1. Transaction State Change

Transaction Begin

When a transaction begins, a method Begin of class com.arjuna.ats.arjuna.coordinator.BasicAction is executed and presented in the log with the message BasicAction::Begin() for action-id <transaction uid>.

Transaction Commit

When a transaction commits, a method Commit of class com.arjuna.ats.arjuna.coordinator.BasicAction is executed and presented in the log with the message BasicAction::Commit() for action-id <transaction uid>.

Transaction Rollback

When a transaction rolls back, a method Rollback of class com.arjuna.ats.arjuna.coordinator.BasicAction is executed and presented in the log with the message BasicAction::Rollback() for action-id <transaction uid>.

Transaction Timeout

When a transaction times out, a method doCancellations of com.arjuna.ats.arjuna.coordinator.TransactionReaper is executed and presented in log as Reaper Worker <thread id> attempting to cancel <transaction uid>. You will then see the same thread rolling back the transaction as shown above.

11.6.3.2. Configuring Logging for the Transactions Subsystem

You can control the amount of information logged about transactions, independent of other logging settings in JBoss EAP. You can configure the logging settings using the management console or the management CLI.

Configuring the Transaction Logger Using the Management Console
  1. Navigate to the Logging subsystem configuration.

    1. In the management console, click the Configuration tab. If you use a managed domain, you must first choose the appropriate server profile.
    2. Select the Logging subsystem and click View.
  2. Edit the com.arjuna attributes.

    Select the Log Categories tab. The com.arjuna entry is already present. Select com.arjuna and click Edit in the Attributes section. You can change the log level and choose whether to use parent handlers or not.

    • Log Level:

      As transactions can produce a lot of logging output, the default logging level is set to WARN so that the server log is not overwhelmed by transaction output. If you need to check transaction processing details, use the TRACE log level so that transaction IDs are shown.

    • Use Parent Handlers:

      Parent handler indicates whether the logger should send its output to its parent logger. The default behavior is true.

  3. Click Save to save the changes.
Configuring the Transaction Logger Using the Management CLI

Use the following command to set the logging level from the management CLI. For a standalone server, remove the /profile=default from the command.

/profile=default/subsystem=logging/logger=com.arjuna:write-attribute(name=level,value=VALUE)

11.6.4. Browse and Manage Transactions

The management CLI supports the ability to browse and manipulate transaction records. This functionality is provided by the interaction between the TM and the management API of JBoss EAP.

The TM stores information about each pending transaction and the participants involved the transaction, in a persistent storage called the object store. The management API exposes the object store as a resource called the log-store. An API operation called probe reads the transaction logs and creates a node path for each record. You can call the probe command manually, whenever you need to refresh the log-store. It is normal for transaction logs to appear and disappear quickly.

Refresh the Log Store

This command refreshes the log store for server groups which use the profile default in a managed domain. For a standalone server, remove the profile=default from the command.

/profile=default/subsystem=transactions/log-store=log-store/:probe
View All Prepared Transactions

To view all prepared transactions, first refresh the log store (see Refresh the Log Store), then run the following command, which functions similarly to a file system ls command.

ls /profile=default/subsystem=transactions/log-store=log-store/transactions

Or

/host=master/server=server-one/subsystem=transactions/log-store=log-store:read-children-names(child-type=transactions)

Each transaction is shown, along with its unique identifier. Individual operations can be run against an individual transaction (see Manage a Transaction).

11.6.4.1. Manage a Transaction

View the Attributes of a Transaction

To view information about a transaction, such as its JNDI name, EIS product name and version, or its status, use the :read-resource management CLI command.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9:read-resource
View the Participants of a Transaction

Each transaction log contains a child element called participants. Use the read-resource management CLI command on this element to see the participants of the transaction. Participants are identified by their JNDI names.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9/participants=java\:\/JmsXA:read-resource

The result may look similar to this:

{
   "outcome" => "success",
   "result" => {
       "eis-product-name" => "ActiveMQ",
       "eis-product-version" => "2.0",
       "jndi-name" => "java:/JmsXA",
       "status" => "HEURISTIC",
       "type" => "/StateManager/AbstractRecord/XAResourceRecord"
   }
}

The outcome status shown here is in a HEURISTIC state and is eligible for recovery. See Recover a Transaction for more details.

In special cases it is possible to create orphan records in the object store, that is XAResourceRecords, which do not have any corresponding transaction record in the log. For example, XA resource prepared but crashed before the TM recorded and is inaccessible for the domain management API. To access such records you need to set management option expose-all-logs to true. This option is not saved in management model and is restored to false when the server is restarted.

/profile=default/subsystem=transactions/log-store=log-store:write-attribute(name=expose-all-logs, value=true)

You can use this alternate command, which shows participant IDs of transaction in an aggregated form.

/host=master/server=server-one/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9:read-children-names(child-type=participants)
Delete a Transaction

Each transaction log supports a :delete operation, to delete the transaction log representing the transaction.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9:delete
Recover a Transaction

Each transaction participant supports recovery via the :recover management CLI command.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9/participants=2:recover
  • If the transaction’s status is HEURISTIC, the recovery operation changes the state to PREPARE and triggers a recovery.
  • If one of the transaction’s participants is heuristic, the recovery operation tries to replay the commit operation. If successful, the participant is removed from the transaction log. You can verify this by re-running the :probe operation on the log-store and checking that the participant is no longer listed. If this is the last participant, the transaction is also deleted.
Refresh the status of a transaction which needs recovery

If a transaction needs recovery, you can use the :refresh management CLI command to be sure it still requires recovery, before attempting the recovery.

/profile=default/subsystem=transactions/log-store=log-store/transactions=0\:ffff7f000001\:-b66efc2\:4f9e6f8f\:9/participants=2:refresh

11.6.5. View Transaction Statistics

If transaction manager statistics are enabled, you can view statistics on processed transactions by the transaction manager. See Configuring the Transaction Manager for information about how to enable transaction manager statistics.

You can view statistics using either the management console or the management CLI. In the management console, transaction statistics are available by navigating to the Transactions subsystem from the Runtime tab. Not all statistics are available from the management console.

The following table shows each available statistic and its description.

Table 11.2. Transactions Subsystem Statistics

StatisticDescription

number-of-transactions

The total number of transactions processed by the transaction manager on this server.

number-of-committed-transactions

The number of committed transactions processed by the transaction manager on this server.

number-of-aborted-transactions

The number of aborted transactions processed by the transaction manager on this server.

number-of-timed-out-transactions

The number of timed out transactions processed by the transaction manager on this server. The number of timed out transactions is calculated to number of aborted transactions too.

number-of-heuristics

Number of transactions in a heuristic state.

number-of-inflight-transactions

Number of transactions which have begun but not yet terminated.

number-of-application-rollbacks

The number of failed transactions whose failure origin was an application.

number-of-resource-rollbacks

The number of failed transactions whose failure origin was a resource.

11.7. Transactions Usage In Practice

11.7.1. Transactions Usage Overview

The following procedures are useful when you need to use transactions in your application.

11.7.2. Control Transactions

Introduction

This list of procedures outlines the different ways to control transactions in your applications which use JTA APIs.

11.7.3. Begin a Transaction

This procedure shows how to begin a new transaction. The API is the same either you run Transaction Manager (TM) configured with JTA or JTS.

  1. Get an instance of UserTransaction

    You can get the instance using JNDI, injection, or an EJB’s context, if the EJB uses bean-managed transactions, by means of a @TransactionManagement(TransactionManagementType.BEAN) annotation.

    1. JNDI

      new InitialContext().lookup("java:comp/UserTransaction")
    2. Injection

      @Resource UserTransaction userTransaction;
    3. Context

      • In a stateless/stateful bean:

        @Resource SessionContext ctx;
        ctx.getUserTransaction();
      • In a message-driven bean:

        @Resource MessageDrivenContext ctx;
        ctx.getUserTransaction()
  2. Call UserTransaction.begin() after you connect to your datasource

    try {
        System.out.println("\nCreating connection to database: "+url);
        stmt = conn.createStatement();  // non-tx statement
        try {
            System.out.println("Starting top-level transaction.");
            userTransaction.begin();
            stmtx = conn.createStatement(); // will be a tx-statement
            ...
        }
    }
    Participate in an existing transaction using the JTS specification
    One of the benefits of EJBs (either used with CMT or BMT) is that the container manages all the internals of the transactional processing, that is, you are free from taking care of transaction being part of XA transaction or transaction distribution amongst JBoss EAP containers.

Result

The transaction begins. All uses of your datasource until you commit or roll back the transaction are transactional.

For a full example, see JTA Transaction Example.

11.7.4. Nested Transactions

Nested transactions allow an application to create a transaction that is embedded in an existing transaction. In this model, multiple subtransactions can be embedded recursively in a transaction. Subtransactions can be committed or rolled back without committing or rolling back the parent transaction. However, the results of a commit operation are contingent upon the commitment of all the transaction’s ancestors.

For implementation specific information, see the Narayana Project Documentation.

Nested transactions are available only when used with the JTS specification. Nested transactions are not a supported feature of JBoss EAP application server. In addition, many database vendors do not support nested transactions, so consult your database vendor before you add nested transactions to your application.

11.7.5. Commit a Transaction

This procedure shows how to commit a transaction using the Java Transaction API (JTA).

Pre-requisites

You must begin a transaction before you can commit it. For information on how to begin a transaction, refer to Begin a Transaction.

  1. Call the commit() method on the UserTransaction

    When you call the commit() method on the UserTransaction, the TM attempts to commit the transaction.

    @Inject
    private UserTransaction userTransaction;
    
    public void updateTable(String key, String value) {
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        try {
            userTransaction.begin();
            <!-- Perform some data manipulation using entityManager -->
            ...
            // Commit the transaction
            userTransaction.commit();
        } catch (Exception ex) {
            <!-- Log message or notify Web page -->
            ...
            try {
                userTransaction.rollback();
            } catch (SystemException se) {
                throw new RuntimeException(se);
            }
            throw new RuntimeException(ex);
        } finally {
            entityManager.close();
        }
    }
  2. If you use Container Managed Transactions (CMT), you do not need to manually commit

    If you configure your bean to use Container Managed Transactions, the container will manage the transaction lifecycle for you based on annotations you configure in the code.

    @PersistenceContext
    private EntityManager em;
    
    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public void updateTable(String key, String value)
      <!-- Perform some data manipulation using entityManager -->
      ...
    }

Result

Your datasource commits and your transaction ends, or an exception is thrown.

Note

For a full example, see JTA Transaction Example.

11.7.6. Roll Back a Transaction

This procedure shows how to roll back a transaction using the Java Transaction API (JTA).

Pre-requisites

You must begin a transaction before you can roll it back. For information on how to begin a transaction, refer to Begin a Transaction.

  1. Call the rollback() method on the UserTransaction

    When you call the rollback() method on the UserTransaction, the TM attempts to roll back the transaction and return the data to its previous state.

    @Inject
    private UserTransaction userTransaction;
    
    public void updateTable(String key, String value)
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        try {
            userTransaction.begin():
            <!-- Perform some data manipulation using entityManager -->
              ...
              // Commit the transaction
            userTransaction.commit();
        } catch (Exception ex) {
            <!-- Log message or notify Web page -->
            ...
            try {
                userTransaction.rollback();
            } catch (SystemException se) {
                throw new RuntimeException(se);
            }
            throw new RuntimeException(e);
        } finally {
            entityManager.close();
        }
    }
  2. If you use Container Managed Transactions (CMT), you do not need to manually roll back the transaction

    If you configure your bean to use Container Managed Transactions, the container will manage the transaction lifecycle for you based on annotations you configure in the code.

Note

Rollback for CMT occurs if RuntimeException is thrown. You can also explicitly call the setRollbackOnly method to gain the rollback. Or, use the @ApplicationException(rollback=true) for application exception to rollback.

Result

Your transaction is rolled back by the TM.

Note

For a full example, see JTA Transaction Example.

11.7.7. Handle a Heuristic Outcome in a Transaction

Heuristic transaction outcomes are uncommon and usually have exceptional causes. The word heuristic means "by hand", and that is the way that these outcomes usually have to be handled. See About Heuristic Outcomes for more information about heuristic transaction outcomes.

This procedure shows how to handle a heuristic outcome of a transaction using the Java Transaction API (JTA).

  1. Determine the cause: The over-arching cause of a heuristic outcome in a transaction is that a resource manager promised it could commit or roll-back, and then failed to fulfill the promise. This could be due to a problem with a third-party component, the integration layer between the third-party component and JBoss EAP, or JBoss EAP itself.

    By far, the most common two causes of heuristic errors are transient failures in the environment and coding errors in the code dealing with resource managers.

  2. Fix transient failures in the environment: Typically, if there is a transient failure in your environment, you will know about it before you find out about the heuristic error. This could be a network outage, hardware failure, database failure, power outage, or a host of other things.

    If you experienced the heuristic outcome in a test environment, during stress testing, it provides information about weaknesses in your environment.

    Warning

    JBoss EAP will automatically recover transactions that were in a non-heuristic state at the time of the failure, but it does not attempt to recover heuristic transactions.

  3. Contact resource manager vendors: If you have no obvious failure in your environment, or the heuristic outcome is easily reproducible, it is probably a coding error. Contact third-party vendors to find out if a solution is available. If you suspect the problem is in the TM of JBoss EAP itself, contact Red Hat Global Support Services.
  4. Try to manually recover transaction through the management CLI. For more information, see Recover a Transaction.
  5. In a test environment, delete the logs and restart JBoss EAP: In a test environment, or if you do not care about the integrity of the data, deleting the transaction logs and restarting JBoss EAP gets rid of the heuristic outcome. The transaction logs are located in EAP_HOME/standalone/data/tx-object-store/ for a standalone server, or EAP_HOME/domain/servers/SERVER_NAME/data/tx-object-store in a managed domain, by default. In the case of a managed domain, SERVER_NAME refers to the name of the individual server participating in a server group.

    Note

    The location of the transaction log also depends on the object store in use and the values set for the oject-store-relative-to and object-store-path parameters. For file system logs (such as a standard shadow and Apache ActiveMQ Artemis logs) the default direction location is used, but when using a JDBC object store, the transaction logs are stored in a database.

  6. Resolve the outcome by hand: The process of resolving the transaction outcome by hand is very dependent on the exact circumstance of the failure. Typically, you need to take the following steps, applying them to your situation:

    1. Identify which resource managers were involved.
    2. Examine the state in the TM and the resource managers.
    3. Manually force log cleanup and data reconciliation in one or more of the involved components.

      The details of how to perform these steps are out of the scope of this documentation.

11.7.8. JTA Transaction Error Handling

11.7.8.1. Handle Transaction Errors

Transaction errors are challenging to solve because they are often dependent on timing. Here are some common errors and ideas for troubleshooting them.

Note

These guidelines do not apply to heuristic errors. If you experience heuristic errors, refer to Handle a Heuristic Outcome in a Transaction and contact Red Hat Global Support Services for assistance.

The transaction timed out but the business logic thread did not notice

This type of error often manifests itself when Hibernate is unable to obtain a database connection for lazy loading. If it happens frequently, you can lengthen the timeout value. Refer to Configuring the Transaction Manager.

If that is not feasible, you may be able to tune your external environment to perform more quickly, or restructure your code to be more efficient. Contact Red Hat Global Support Services if you still have trouble with timeouts.

The transaction is already running on a thread, or you receive a NotSupportedException exception

The NotSupportedException exception usually indicates that you attempted to nest a JTA transaction, and this is not supported. If you were not attempting to nest a transaction, it is likely that another transaction was started in a thread pool task, but finished the task without suspending or ending the transaction.

Applications typically use UserTransaction, which handles this automatically. If so, there may be a problem with a framework.

If your code does use TransactionManager or Transaction methods directly, be aware of the following behavior when committing or rolling back a transaction. If your code uses TransactionManager methods to control your transactions, committing or rolling back a transaction disassociates the transaction from the current thread. However, if your code uses Transaction methods, the transaction may not be associated with the running thread, and you need to disassociate it from its threads manually, before returning it to the thread pool.

You are unable to enlist a second local resource
This error happens if you try to enlist a second non-XA resource into a transaction. If you need multiple resources in a transaction, they must be XA.

11.8. Transaction References

11.8.1. JTA Transaction Example

This example illustrates how to begin, commit, and roll back a JTA transaction. You need to adjust the connection and datasource parameters to suit your environment, and set up two test tables in your database.

public class JDBCExample {
    public static void main (String[] args) {
        Context ctx = new InitialContext();
        // Change these two lines to suit your environment.
        DataSource ds = (DataSource)ctx.lookup("jdbc/ExampleDS");
        Connection conn = ds.getConnection("testuser", "testpwd");
        Statement stmt = null; // Non-transactional statement
        Statement stmtx = null; // Transactional statement
        Properties dbProperties = new Properties();

        // Get a UserTransaction
        UserTransaction txn = new InitialContext().lookup("java:comp/UserTransaction");

        try {
            stmt = conn.createStatement();  // non-tx statement

            // Check the database connection.
            try {
                stmt.executeUpdate("DROP TABLE test_table");
                stmt.executeUpdate("DROP TABLE test_table2");
            }
            catch (Exception e) {
                throw new RuntimeException(e);
                // assume not in database.
            }

            try {
                stmt.executeUpdate("CREATE TABLE test_table (a INTEGER,b INTEGER)");
                stmt.executeUpdate("CREATE TABLE test_table2 (a INTEGER,b INTEGER)");
            }
            catch (Exception e) {
                throw new RuntimeException(e);
            }

            try {
                System.out.println("Starting top-level transaction.");

                txn.begin();

                stmtx = conn.createStatement(); // will be a tx-statement

                // First, we try to roll back changes

                System.out.println("\nAdding entries to table 1.");

                stmtx.executeUpdate("INSERT INTO test_table (a, b) VALUES (1,2)");

                ResultSet res1 = null;

                System.out.println("\nInspecting table 1.");

                res1 = stmtx.executeQuery("SELECT * FROM test_table");

                while (res1.next()) {
                    System.out.println("Column 1: "+res1.getInt(1));
                    System.out.println("Column 2: "+res1.getInt(2));
                }
                System.out.println("\nAdding entries to table 2.");

                stmtx.executeUpdate("INSERT INTO test_table2 (a, b) VALUES (3,4)");
                res1 = stmtx.executeQuery("SELECT * FROM test_table2");

                System.out.println("\nInspecting table 2.");

                while (res1.next()) {
                    System.out.println("Column 1: "+res1.getInt(1));
                    System.out.println("Column 2: "+res1.getInt(2));
                }

                System.out.print("\nNow attempting to rollback changes.");

                txn.rollback();

                // Next, we try to commit changes
                txn.begin();
                stmtx = conn.createStatement();
                System.out.println("\nAdding entries to table 1.");
                stmtx.executeUpdate("INSERT INTO test_table (a, b) VALUES (1,2)");
                ResultSet res2 = null;

                System.out.println("\nNow checking state of table 1.");

                res2 = stmtx.executeQuery("SELECT * FROM test_table");

                while (res2.next()) {
                    System.out.println("Column 1: "+res2.getInt(1));
                    System.out.println("Column 2: "+res2.getInt(2));
                }

                System.out.println("\nNow checking state of table 2.");

                stmtx = conn.createStatement();

                res2 = stmtx.executeQuery("SELECT * FROM test_table2");

                while (res2.next()) {
                    System.out.println("Column 1: "+res2.getInt(1));
                    System.out.println("Column 2: "+res2.getInt(2));
                }

                txn.commit();
            }
            catch (Exception ex) {
                throw new RuntimeException(ex);

            }
        }
        catch (Exception sysEx) {
            sysEx.printStackTrace();
            System.exit(0);
        }
    }
}

11.8.2. Transaction API Documentation

The transaction JTA API documentation is available as javadoc at the following location:

If you use Red Hat JBoss Developer Studio to develop your applications, the API documentation is included in the Help menu.

Chapter 12. Java Persistence API (JPA)

12.1. About Java Persistence API (JPA)

The Java Persistence API (JPA) is a Java specification for accessing, persisting, and managing data between Java objects or classes and a relational database. The JPA specification recognizes the interest and the success of the transparent object or relational mapping paradigm. It standardizes the basic APIs and the metadata needed for any object or relational persistence mechanism.

Note

JPA itself is just a specification, not a product; it cannot perform persistence or anything else by itself. JPA is just a set of interfaces, and requires an implementation.

12.2. About Hibernate Core

Hibernate Core is an object-relational mapping framework for the Java language. It provides a framework for mapping an object-oriented domain model to a relational database, allowing applications to avoid direct interaction with the database. Hibernate solves object-relational impedance mismatch problems by replacing direct, persistent database accesses with high-level object handling functions.

12.3. Hibernate EntityManager

Hibernate EntityManager implements the programming interfaces and lifecycle rules as defined by the Java Persistence 2.1 specification. Together with Hibernate Annotations, this wrapper implements a complete (and standalone) JPA persistence solution on top of the mature Hibernate Core. You may use a combination of all three together, annotations without JPA programming interfaces and lifecycle, or even pure native Hibernate Core, depending on the business and technical needs of your project. You can at all times fall back to Hibernate native APIs, or if required, even to native JDBC and SQL. It provides JBoss EAP with a complete Java Persistence solution.

JBoss EAP is 100% compliant with the Java Persistence 2.1 specification. Hibernate also provides additional features to the specification. To get started with JPA and JBoss EAP, see the bean-validation, greeter, and kitchensink quickstarts that ship with JBoss EAP. For information about how to download and run the quickstarts, see Using the Quickstart Examples.

Persistence in JPA is available in containers like EJB 3 or the more modern CDI, Java Context and Dependency Injection, as well as in standalone Java SE applications that execute outside of a particular container. The following programming interfaces and artifacts are available in both environments.

EntityManagerFactory
An entity manager factory provides entity manager instances, all instances are configured to connect to the same database, to use the same default settings as defined by the particular implementation, etc. You can prepare several entity manager factories to access several data stores. This interface is similar to the SessionFactory in native Hibernate.
EntityManager
The EntityManager API is used to access a database in a particular unit of work. It is used to create and remove persistent entity instances, to find entities by their primary key identity, and to query over all entities. This interface is similar to the Session in Hibernate.
Persistence context
A persistence context is a set of entity instances in which for any persistent entity identity there is a unique entity instance. Within the persistence context, the entity instances and their lifecycle is managed by a particular entity manager. The scope of this context can either be the transaction, or an extended unit of work.
Persistence unit
The set of entity types that can be managed by a given entity manager is defined by a persistence unit. A persistence unit defines the set of all classes that are related or grouped by the application, and which must be collocated in their mapping to a single data store.
Container-managed entity manager
An entity manager whose lifecycle is managed by the container.
Application-managed entity manager
An entity manager whose lifecycle is managed by the application.
JTA entity manager
Entity manager involved in a JTA transaction.
Resource-local entity manager
Entity manager using a resource transaction (not a JTA transaction).

12.4. Create a Simple JPA Application

Follow the procedure below to create a simple JPA application in Red Hat Developer studio.

  1. Create a JPA project in JBoss Developer Studio.

    1. In Red Hat JBoss Developer Studio, click File-→ New -→ Project. Find JPA in the list, expand it, and select JPA Project. You are presented with the following dialog.

      Figure 12.1. New JPA Project Dialog

      This is the new JPA Project dialog.
    2. Enter a Project name.
    3. Select a Target runtime. If no target runtime is available, follow these instructions to define a new server and runtime: Add the JBoss EAP Server Using Define New Server .
    4. Under JPA version, ensure 2.1 is selected.
    5. Under Configuration, choose Basic JPA Configuration.
    6. Click Finish.
    7. If prompted, choose whether you wish to associate this type of project with the JPA perspective window.
  2. Create and configure a new persistence settings file.

    1. Open an EJB 3.x project in Red Hat JBoss Developer Studio.
    2. Right click the project root directory in the Project Explorer panel.
    3. Select NewOther…​.
    4. Select XML File from the XML folder and click Next.
    5. Select the ejbModule/META-INF/ folder as the parent directory.
    6. Name the file persistence.xml and click Next.
    7. Select Create XML file from an XML schema file and click Next.
    8. Select http://java.sun.com/xml/ns/persistence/persistence_2.0.xsd from the Select XML Catalog entry list and click Next.

      Figure 12.2. Persistence XML Schema

      Persistence XML Schema
    9. Click Finish to create the file. The persistence.xml has been created in the META-INF/ folder and is ready to be configured.

      Example Persistence Settings File

      <persistence xmlns="http://java.sun.com/xml/ns/persistence"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
         version="2.0">
         <persistence-unit name="example" transaction-type="JTA">
            <provider>org.hibernate.ejb.HibernatePersistence</provider>
            <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source>
            <mapping-file>ormap.xml</mapping-file>
            <jar-file>TestApp.jar</jar-file>
            <class>org.test.Test</class>
            <shared-cache-mode>NONE</shared-cache-mode>
            <validation-mode>CALLBACK</validation-mode>
            <properties>
               <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
               <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
            </properties>
         </persistence-unit>
      </persistence>

12.5. Configuration

12.5.1. Hibernate Configuration Properties

Table 12.1. Hibernate Java Properties

Property NameDescription

hibernate.dialect

The classname of a Hibernate org.hibernate.dialect.Dialect. Allows Hibernate to generate SQL optimized for a particular relational database.

In most cases Hibernate will be able to choose the correct org.hibernate.dialect.Dialect implementation, based on the JDBC metadata returned by the JDBC driver.

hibernate.show_sql

Boolean. Writes all SQL statements to console. This is an alternative to setting the log category org.hibernate.SQL to debug.

hibernate.format_sql

Boolean. Pretty print the SQL in the log and console.

hibernate.default_schema

Qualify unqualified table names with the given schema/tablespace in generated SQL.

hibernate.default_catalog

Qualifies unqualified table names with the given catalog in generated SQL.

hibernate.session_factory_name

The org.hibernate.SessionFactory will be automatically bound to this name in JNDI after it has been created. For example, jndi/composite/name.

hibernate.max_fetch_depth

Sets a maximum depth for the outer join fetch tree for single-ended associations (one-to-one, many-to-one). A 0 disables default outer join fetching. The recommended value is between 0 and 3.

hibernate.default_batch_fetch_size

Sets a default size for Hibernate batch fetching of associations. The recommended values are 4, 8, and 16.

hibernate.default_entity_mode

Sets a default mode for entity representation for all sessions opened from this SessionFactory. Values include: dynamic-map, dom4j, pojo.

hibernate.order_updates

Boolean. Forces Hibernate to order SQL updates by the primary key value of the items being updated. This will result in fewer transaction deadlocks in highly concurrent systems.

hibernate.generate_statistics

Boolean. If enabled, Hibernate will collect statistics useful for performance tuning.

hibernate.use_identifier_rollback

Boolean. If enabled, generated identifier properties will be reset to default values when objects are deleted.

hibernate.use_sql_comments

Boolean. If turned on, Hibernate will generate comments inside the SQL, for easier debugging. Default value is false.

hibernate.id.new_generator_mappings

Boolean. This property is relevant when using @GeneratedValue. It indicates whether or not the new IdentifierGenerator implementations are used for javax.persistence.GenerationType.AUTO, javax.persistence.GenerationType.TABLE and javax.persistence.GenerationType.SEQUENCE. Default value is true.

hibernate.ejb.naming_strategy

Chooses the org.hibernate.cfg.NamingStrategy implementation when using Hibernate EntityManager. hibernate.ejb.naming_strategy is no longer supported in Hibernate 5.0. If used, a deprecation message will be logged indicating that it is no longer supported and has been removed in favor of the split ImplicitNamingStrategy and PhysicalNamingStrategy.

If the application does not use EntityManager, follow the instructions here to configure the NamingStrategy: Hibernate Reference Documentation - Naming Strategies.

For an example on native bootstrapping using MetadataBuilder and applying the implicit naming strategy, see http://docs.jboss.org/hibernate/orm/5.0/userguide/html_single/Hibernate_User_Guide.html#bootstrap-native-metadata in the Hibernate 5.0 documentation. The physical naming strategy can be applied by using MetadataBuilder.applyPhysicalNamingStrategy(). For further details on org.hibernate.boot.MetadataBuilder, see https://docs.jboss.org/hibernate/orm/5.0/javadocs/.

hibernate.implicit_naming_strategy

Specifies the org.hibernate.boot.model.naming.ImplicitNamingStrategy class to be used. hibernate.implicit_naming_strategy can also be used to configure a custom class that implements ImplicitNamingStrategy. Following short names are defined for this setting:

  • default - ImplicitNamingStrategyJpaCompliantImpl
  • jpa - ImplicitNamingStrategyJpaCompliantImpl
  • legacy-jpa - ImplicitNamingStrategyLegacyJpaImpl
  • legacy-hbm - ImplicitNamingStrategyLegacyHbmImpl
  • component-path - ImplicitNamingStrategyComponentPathImpl

The default setting is defined by the ImplicitNamingStrategy in the default short name. If the default setting is empty, the fallback is to use ImplicitNamingStrategyJpaCompliantImpl.

hibernate.physical_naming_strategy

Pluggable strategy contract for applying physical naming rules for database object names. Specifies the PhysicalNamingStrategy class to be used. PhysicalNamingStrategyStandardImpl is used by default. hibernate.physical_naming_strategy can also be used to configure a custom class that implements PhysicalNamingStrategy.

Important

For hibernate.id.new_generator_mappings, new applications should keep the default value of true. Existing applications that used Hibernate 3.3.x may need to change it to false to continue using a sequence object or table based generator, and maintain backward compatibility.

12.5.2. Hibernate JDBC and Connection Properties

Table 12.2. Properties

Property NameDescription

hibernate.jdbc.fetch_size

A non-zero value that determines the JDBC fetch size (calls Statement.setFetchSize()).

hibernate.jdbc.batch_size

A non-zero value enables use of JDBC2 batch updates by Hibernate. The recommended values are between 5 and 30.

hibernate.jdbc.batch_versioned_data

Boolean. Set this property to true if the JDBC driver returns correct row counts from executeBatch(). Hibernate will then use batched DML for automatically versioned data. Default value is to false.

hibernate.jdbc.factory_class

Select a custom org.hibernate.jdbc.Batcher. Most applications will not need this configuration property.

hibernate.jdbc.use_scrollable_resultset

Boolean. Enables use of JDBC2 scrollable resultsets by Hibernate. This property is only necessary when using user-supplied JDBC connections. Hibernate uses connection metadata otherwise.

hibernate.jdbc.use_streams_for_binary

Boolean. This is a system-level property. Use streams when writing/reading binary or serializable types to/from JDBC.

hibernate.jdbc.use_get_generated_keys

Boolean. Enables use of JDBC3 PreparedStatement.getGeneratedKeys() to retrieve natively generated keys after insert. Requires JDBC3+ driver and JRE1.4+. Set to false if JDBC driver has problems with the Hibernate identifier generators. By default, it tries to determine the driver capabilities using connection metadata.

hibernate.connection.provider_class

The classname of a custom org.hibernate.connection.ConnectionProvider which provides JDBC connections to Hibernate.

hibernate.connection.isolation

Sets the JDBC transaction isolation level. Check java.sql.Connection for meaningful values, but note that most databases do not support all isolation levels and some define additional, non-standard isolations. Standard values are 1, 2, 4, 8.

hibernate.connection.autocommit

Boolean. This property is not recommended for use. Enables autocommit for JDBC pooled connections.

hibernate.connection.release_mode

Specifies when Hibernate should release JDBC connections. By default, a JDBC connection is held until the session is explicitly closed or disconnected. The default value auto will choose after_statement for the JTA and CMT transaction strategies, and after_transaction for the JDBC transaction strategy.

Available values are auto (default), on_close, after_transaction, after_statement.

This setting only affects Session returned from SessionFactory.openSession. For Session obtained through SessionFactory.getCurrentSession, the CurrentSessionContext implementation configured for use controls the connection release mode for that Session.

hibernate.connection.<propertyName>

Pass the JDBC property <propertyName> to DriverManager.getConnection().

hibernate.jndi.<propertyName>

Pass the property <propertyName> to the JNDI InitialContextFactory.

12.5.3. Hibernate Cache Properties

Table 12.3. Properties

Property NameDescription

hibernate.cache.region.factory_class

The classname of a custom CacheProvider.

hibernate.cache.use_minimal_puts

Boolean. Optimizes second-level cache operation to minimize writes, at the cost of more frequent reads. This setting is most useful for clustered caches and, in Hibernate3, is enabled by default for clustered cache implementations.

hibernate.cache.use_query_cache

Boolean. Enables the query cache. Individual queries still have to be set cacheable.

hibernate.cache.use_second_level_cache

Boolean. Used to completely disable the second level cache, which is enabled by default for classes that specify a <cache> mapping.

hibernate.cache.query_cache_factory

The classname of a custom QueryCache interface. The default value is the built-in StandardQueryCache.

hibernate.cache.region_prefix

A prefix to use for second-level cache region names.

hibernate.cache.use_structured_entries

Boolean. Forces Hibernate to store data in the second-level cache in a more human-friendly format.

hibernate.cache.default_cache_concurrency_strategy

Setting used to give the name of the default org.hibernate.annotations.CacheConcurrencyStrategy to use when either @Cacheable or @Cache is used. @Cache(strategy="..") is used to override this default.

12.5.4. Hibernate Transaction Properties

Table 12.4. Properties

Property NameDescription

hibernate.transaction.factory_class

The classname of a TransactionFactory to use with Hibernate Transaction API. Defaults to JDBCTransactionFactory).

jta.UserTransaction

A JNDI name used by JTATransactionFactory to obtain the JTA UserTransaction from the application server.

hibernate.transaction.manager_lookup_class

The classname of a TransactionManagerLookup. It is required when JVM-level caching is enabled or when using hilo generator in a JTA environment.

hibernate.transaction.flush_before_completion

Boolean. If enabled, the session will be automatically flushed during the before completion phase of the transaction. Built-in and automatic session context management is preferred.

hibernate.transaction.auto_close_session

Boolean. If enabled, the session will be automatically closed during the after completion phase of the transaction. Built-in and automatic session context management is preferred.

12.5.5. Miscellaneous Hibernate Properties

Table 12.5. Properties

Property NameDescription

hibernate.current_session_context_class

Supply a custom strategy for the scoping of the "current" Session. Values include jta, thread, managed, custom.Class.

hibernate.query.factory_class

Chooses the HQL parser implementation: org.hibernate.hql.internal.ast.ASTQueryTranslatorFactory or org.hibernate.hql.internal.classic.ClassicQueryTranslatorFactory.

hibernate.query.substitutions

Used to map from tokens in Hibernate queries to SQL tokens (tokens might be function or literal names). For example, hqlLiteral=SQL_LITERAL, hqlFunction=SQLFUNC.

hibernate.hbm2ddl.auto

Automatically validates or exports schema DDL to the database when the SessionFactory is created. With create-drop, the database schema will be dropped when the SessionFactory is closed explicitly. Property value options are validate, update, create, create-drop

hibernate.hbm2ddl.import_files

Comma-separated names of the optional files containing SQL DML statements executed during the SessionFactory creation. This is useful for testing or demonstrating. For example, by adding INSERT statements, the database can be populated with a minimal set of data when it is deployed. An example value is /humans.sql,/dogs.sql.

File order matters, as the statements of a given file are executed before the statements of the following files. These statements are only executed if the schema is created (i.e. if hibernate.hbm2ddl.auto is set to create or create-drop).

hibernate.hbm2ddl.import_files_sql_extractor

The classname of a custom ImportSqlCommandExtractor. Defaults to the built-in SingleLineSqlCommandExtractor. This is useful for implementing a dedicated parser that extracts a single SQL statement from each import file. Hibernate also provides MultipleLinesSqlCommandExtractor, which supports instructions/comments and quoted strings spread over multiple lines (mandatory semicolon at the end of each statement).

hibernate.bytecode.use_reflection_optimizer

Boolean. This is a system-level property, which cannot be set in the hibernate.cfg.xml file. Enables the use of bytecode manipulation instead of runtime reflection. Reflection can sometimes be useful when troubleshooting. Hibernate always requires either cglib or javassist even if the optimizer is turned off.

hibernate.bytecode.provider

Both javassist or cglib can be used as byte manipulation engines. The default is javassist. Property value is either javassist or cglib

12.5.6. Hibernate SQL Dialects

Important

The hibernate.dialect property should be set to the correct org.hibernate.dialect.Dialect subclass for the application database. If a dialect is specified, Hibernate will use sensible defaults for some of the other properties. This means that they do not have to be specified manually.

Table 12.6. SQL Dialects (hibernate.dialect)

RDBMSDialect

DB2

org.hibernate.dialect.DB2Dialect

DB2 AS/400

org.hibernate.dialect.DB2400Dialect

DB2 OS390

org.hibernate.dialect.DB2390Dialect

Firebird

org.hibernate.dialect.FirebirdDialect

FrontBase

org.hibernate.dialect.FrontbaseDialect

H2 Database

org.hibernate.dialect.H2Dialect

HypersonicSQL

org.hibernate.dialect.HSQLDialect

Informix

org.hibernate.dialect.InformixDialect

Ingres

org.hibernate.dialect.IngresDialect

Interbase

org.hibernate.dialect.InterbaseDialect

MariaDB 10

org.hibernate.dialect.MySQL57InnoDBDialect

Mckoi SQL

org.hibernate.dialect.MckoiDialect

Microsoft SQL Server 2000

org.hibernate.dialect.SQLServerDialect

Microsoft SQL Server 2005

org.hibernate.dialect.SQLServer2005Dialect

Microsoft SQL Server 2008

org.hibernate.dialect.SQLServer2008Dialect

Microsoft SQL Server 2012

org.hibernate.dialect.SQLServer2012Dialect

Microsoft SQL Server 2014

org.hibernate.dialect.SQLServer2012Dialect

MySQL5

org.hibernate.dialect.MySQL5Dialect

MySQL5.7

org.hibernate.dialect.MySQL57InnoDBDialect

MySQL5 with InnoDB

org.hibernate.dialect.MySQL5InnoDBDialect

MySQL with MyISAM

org.hibernate.dialect.MySQLMyISAMDialect

Oracle (any version)

org.hibernate.dialect.OracleDialect

Oracle 9i

org.hibernate.dialect.Oracle9iDialect

Oracle 10g

org.hibernate.dialect.Oracle10gDialect

Oracle 11g

org.hibernate.dialect.Oracle10gDialect

Oracle 12c

org.hibernate.dialect.Oracle12cDialect

Pointbase

org.hibernate.dialect.PointbaseDialect

PostgreSQL

org.hibernate.dialect.PostgreSQLDialect

PostgreSQL 9.2

org.hibernate.dialect.PostgreSQL9Dialect

PostgreSQL 9.3

org.hibernate.dialect.PostgreSQL9Dialect

PostgreSQL 9.4

org.hibernate.dialect.PostgreSQL94Dialect

Postgres Plus Advanced Server

org.hibernate.dialect.PostgresPlusDialect

Progress

org.hibernate.dialect.ProgressDialect

SAP DB

org.hibernate.dialect.SAPDBDialect

Sybase

org.hibernate.dialect.SybaseASE15Dialect

Sybase 15.7

org.hibernate.dialect.SybaseASE157Dialect

Sybase Anywhere

org.hibernate.dialect.SybaseAnywhereDialect

12.6. Second-Level Caches

12.6.1. About Second-Level Caches

A second-level cache is a local data store that holds information persisted outside the application session. The cache is managed by the persistence provider, improving run-time by keeping the data separate from the application.

JBoss EAP supports caching for the following purposes:

  • Web Session Clustering
  • Stateful Session Bean Clustering
  • SSO Clustering
  • Hibernate Second Level Cache

Each cache container defines a "repl" and a "dist" cache. These caches should not be used directly by user applications.

12.6.2. Configure a Second Level Cache for Hibernate

The configuration of Infinispan to act as the second level cache for Hibernate can be done in two ways:

  • Through Hibernate native applications, using hibernate.cfg.xml
  • Through JPA applications, using persistence.xml
Configuring a Second Level Cache for Hibernate Using Hibernate Native Applications
  1. Create the hibernate.cfg.xml in the deployment’s class path.
  2. Add the following XML to the hibernate.cfg.xml. The XML needs to be within the <session-factory> tag:

    <property name="hibernate.cache.use_second_level_cache">true</property>
    <property name="hibernate.cache.use_query_cache">true</property>
    <property name="hibernate.cache.region.factory_class">org.jboss.as.jpa.hibernate5.infinispan.InfinispanRegionFactory</property>
Configuring a Second Level Cache for Hibernate Using JPA Applications
  1. See Create a Simple JPA Application for details on how to create a Hibernate configuration file in Red Hat JBoss Developer Studio.
  2. Add the following to the persistence.xml file:

    <persistence-unit name="...">
      (...) <!-- other configuration -->
      <shared-cache-mode>$SHARED_CACHE_MODE</shared-cache-mode>
      <properties>
        <property name="hibernate.cache.use_second_level_cache" value="true" />
        <property name="hibernate.cache.use_query_cache" value="true" />
      </properties>
    </persistence-unit>
    Note

    The following can be value of $SHARED_CACHE_MODE:

    • ALL - All entities should be considered cacheable.
    • ENABLE_SELECTIVE - Only entities marked as cacheable should be considered cacheable.
    • DISABLE_SELECTIVE - All entities except the ones explicitly marked as not cacheable, should be considered cacheable.

12.7. Hibernate Annotations

The org.hibernate.annotations package contains some annotations which are offered by Hibernate, on top of the standard JPA annotations.

Table 12.7. General Annotations

AnnotationDescription

Check

Arbitrary SQL check constraints which can be defined at the class, property or collection level.

Immutable

Mark an Entity or a Collection as immutable. No annotation means the element is mutable.

An immutable entity may not be updated by the application. Updates to an immutable entity will be ignored, but no exception is thrown.

@Immutable placed on a collection makes the collection immutable, meaning additions and deletions to and from the collection are not allowed. A HibernateException is thrown in this case.

Table 12.8. Caching Entities

AnnotationDescription

Cache

Add caching strategy to a root entity or a collection.

Table 12.9. Collection Related Annotations

AnnotationDescription

MapKeyType

Defines the type of key of a persistent map.

ManyToAny

Defines a ToMany association pointing to different entity types. Matching the entity type is done through a metadata discriminator column. This kind of mapping should be only marginal.

OrderBy

Order a collection using SQL ordering (not HQL ordering).

OnDelete

Strategy to use on collections, arrays and on joined subclasses delete. OnDelete of secondary tables is currently not supported.

Persister

Specify a custom persister.

Sort

Collection sort (Java level sorting).

Where

Where clause to add to the element Entity or target entity of a collection. The clause is written in SQL.

WhereJoinTable

Where clause to add to the collection join table. The clause is written in SQL.

Table 12.10. Custom SQL for CRUD Operations

AnnotationDescription

Loader

Overwrites Hibernate default FIND method.

SQLDelete

Overwrites the Hibernate default DELETE method.

SQLDeleteAll

Overwrites the Hibernate default DELETE ALL method.

SQLInsert

Overwrites the Hibernate default INSERT INTO method.

SQLUpdate

Overwrites the Hibernate default UPDATE method.

Subselect

Maps an immutable and read-only entity to a given SQL subselect expression.

Synchronize

Ensures that auto-flush happens correctly and that queries against the derived entity do not return stale data. Mostly used with Subselect.

Table 12.11. Entity

AnnotationDescription

Cascade

Apply a cascade strategy on an association.

Entity

Adds additional metadata that may be needed beyond what is defined in the standard @Entity.

  • mutable: whether this entity is mutable or not
  • dynamicInsert: allow dynamic SQL for inserts
  • dynamicUpdate: allow dynamic SQL for updates
  • selectBeforeUpdate: Specifies that Hibernate should never perform an SQL UPDATE unless it is certain that an object is actually modified.
  • polymorphism: whether the entity polymorphism is of PolymorphismType.IMPLICIT (default) or PolymorphismType.EXPLICIT
  • optimisticLock: optimistic locking strategy (OptimisticLockType.VERSION, OptimisticLockType.NONE, OptimisticLockType.DIRTY or OptimisticLockType.ALL)

    Note

    The annotation "Entity" is deprecated and scheduled for removal in future releases. Its individual attributes or values should become annotations.

Polymorphism

Used to define the type of polymorphism Hibernate will apply to entity hierarchies.

Proxy

Lazy and proxy configuration of a particular class.

Table

Complementary information to a table either primary or secondary.

Tables

Plural annotation of Table.

Target

Defines an explicit target, avoiding reflection and generics resolving.

Tuplizer

Defines a tuplizer for an entity or a component.

Tuplizers

Defines a set of tuplizers for an entity or a component.

Table 12.12. Fetching

AnnotationDescription

BatchSize

Batch size for SQL loading.

FetchProfile

Defines the fetching strategy profile.

FetchProfiles

Plural annotation for @FetchProfile.

Table 12.13. Filters

AnnotationDescription

Filter

Adds filters to an entity or a target entity of a collection.

FilterDef

Filter definition.

FilterDefs

Array of filter definitions.

FilterJoinTable

Adds filters to a join table collection.

FilterJoinTables

Adds multiple @FilterJoinTable to a collection.

Filters

Adds multiple @Filter.

ParamDef

A parameter definition.

Table 12.14. Primary Keys

AnnotationDescription

Generated

This annotated property is generated by the database.

GenericGenerator

Generator annotation describing any kind of Hibernate generator in a detyped manner.

GenericGenerators

Array of generic generator definitions.

NaturalId

Specifies that a property is part of the natural id of the entity.

Parameter

Key/value pattern.

RowId

Support for ROWID mapping feature of Hibernate.

Table 12.15. Inheritance

AnnotationDescription

DiscriminatorFormula

Discriminator formula to be placed at the root entity.

DiscriminatorOptions

Optional annotation to express Hibernate specific discriminator properties.

MetaValue

Maps a given discriminator value to the corresponding entity type.

Table 12.16. Mapping JP-QL/HQL Queries

AnnotationDescription

NamedNativeQueries

Extends NamedNativeQueries to hold Hibernate NamedNativeQuery objects.

NamedNativeQuery

Extends NamedNativeQuery with Hibernate features.

NamedQueries

Extends NamedQueries to hold Hibernate NamedQuery objects.

NamedQuery

Extends NamedQuery with Hibernate features.

Table 12.17. Mapping Simple Properties

AnnotationDescription

AccessType

Property Access type.

Columns

Support an array of columns. Useful for component user type mappings.

ColumnTransformer

Custom SQL expression used to read the value from and write a value to a column. Use for direct object loading/saving as well as queries. The write expression must contain exactly one '?' placeholder for the value.

ColumnTransformers

Plural annotation for @ColumnTransformer. Useful when more than one column is using this behavior.

Table 12.18. Property

AnnotationDescription

Formula

To be used as a replacement for @Column in most places. The formula has to be a valid SQL fragment.

Index

Defines a database index.

JoinFormula

To be used as a replacement for @JoinColumn in most places. The formula has to be a valid SQL fragment.

Parent

Reference the property as a pointer back to the owner (generally the owning entity).

Type

Hibernate Type.

TypeDef

Hibernate Type definition.

TypeDefs

Hibernate Type definition array.

Table 12.19. Single Association Related Annotations

AnnotationDescription

Any

Defines a ToOne association pointing to several entity types. Matching the according entity type is done through a metadata discriminator column. This kind of mapping should be only marginal.

AnyMetaDef

Defines @Any and @ManyToAny metadata.

AnyMetaDefs

Defines @Any and @ManyToAny set of metadata. Can be defined at the entity level or the package level.

Fetch

Defines the fetching strategy used for the given association.

LazyCollection

Defines the lazy status of a collection.

LazyToOne

Defines the lazy status of a ToOne association (i.e. OneToOne or ManyToOne).

NotFound

Action to do when an element is not found on an association.

Table 12.20. Optimistic Locking

AnnotationDescription

OptimisticLock

Whether or not a change of the annotated property will trigger an entity version increment. If the annotation is not present, the property is involved in the optimistic lock strategy (default).

OptimisticLocking

Used to define the style of optimistic locking to be applied to an entity. In a hierarchy, only valid on the root entity.

Source

Optional annotation in conjunction with Version and timestamp version properties. The annotation value decides where the timestamp is generated.

12.8. Hibernate Query Language

12.8.1. About Hibernate Query Language

Introduction to JPQL

The Java Persistence Query Language (JPQL) is a platform-independent object-oriented query language defined as part of the Java Persistence API (JPA) specification. JPQL is used to make queries against entities stored in a relational database. It is heavily inspired by SQL, and its queries resemble SQL queries in syntax, but operate against JPA entity objects rather than directly with database tables.

Introduction to HQL

The Hibernate Query Language (HQL) is a powerful query language, similar in appearance to SQL. Compared with SQL, however, HQL is fully object-oriented and understands notions like inheritance, polymorphism and association.

HQL is a superset of JPQL. An HQL query is not always a valid JPQL query, but a JPQL query is always a valid HQL query.

Both HQL and JPQL are non-type-safe ways to perform query operations. Criteria queries offer a type-safe approach to querying.

12.8.2. About HQL Statements

Both HQL and JPQL allow SELECT, UPDATE, and DELETE statements. HQL additionally allows INSERT statements, in a form similar to a SQL INSERT-SELECT.

Important

Care should be taken when executing bulk update or delete operations because they may result in inconsistencies between the database and the entities in the active persistence context. In general, bulk update and delete operations should only be performed within a transaction in a new persistence context or before fetching or accessing entities whose state might be affected by such operations.

Table 12.21. HQL Statements

StatementDescription

SELECT

The BNF for SELECT statements in HQL is:

select_statement :: =
        [select_clause]
        from_clause
        [where_clause]
        [groupby_clause]
        [having_clause]
        [orderby_clause]

UDPATE

The BNF for UPDATE statement in HQL is the same as it is in JPQL

DELETE

The BNF for DELETE statements in HQL is the same as it is in JPQL

12.8.3. About the INSERT Statement

HQL adds the ability to define INSERT statements. There is no JPQL equivalent to this. The BNF for an HQL INSERT statement is:

insert_statement ::= insert_clause select_statement

insert_clause ::= INSERT INTO entity_name (attribute_list)

attribute_list ::= state_field[, state_field ]*

The attribute_list is analogous to the column specification in the SQL INSERT statement. For entities involved in mapped inheritance, only attributes directly defined on the named entity can be used in the attribute_list. Superclass properties are not allowed and subclass properties do not make sense. In other words, INSERT statements are inherently non-polymorphic.

Warning

The select_statement can be any valid HQL select query, with the caveat that the return types must match the types expected by the insert. Currently, this is checked during query compilation rather than allowing the check to relegate to the database. This can cause problems with Hibernate Types that are equivalent as opposed to equal. For example, this might cause mismatch issues between an attribute mapped as an org.hibernate.type.DateType and an attribute defined as a org.hibernate.type.TimestampType, even though the database might not make a distinction or might be able to handle the conversion.

For the id attribute, the insert statement gives you two options. You can either explicitly specify the id property in the attribute_list, in which case its value is taken from the corresponding select expression, or omit it from the attribute_list in which case a generated value is used. This latter option is only available when using id generators that operate "in the database"; attempting to use this option with any "in memory" type generators will cause an exception during parsing.

For optimistic locking attributes, the insert statement again gives you two options. You can either specify the attribute in the attribute_list in which case its value is taken from the corresponding select expressions, or omit it from the attribute_list in which case the seed value defined by the corresponding org.hibernate.type.VersionType is used.

Example. INSERT Query Statements

String hqlInsert = "insert into DelinquentAccount (id, name) select c.id, c.name from Customer c where ...";
int createdEntities = s.createQuery( hqlInsert ).executeUpdate();

12.8.4. About the FROM Clause

The FROM clause is responsible defining the scope of object model types available to the rest of the query. It also is responsible for defining all the "identification variables" available to the rest of the query.

12.8.5. About the WITH Clause

HQL defines a WITH clause to qualify the join conditions. This is specific to HQL; JPQL does not define this feature.

Example. With Clause

select distinct c
from Customer c
    left join c.orders o
        with o.value > 5000.00

The important distinction is that in the generated SQL the conditions of the with clause are made part of the on clause in the generated SQL as opposed to the other queries in this section where the HQL/JPQL conditions are made part of the where clause in the generated SQL. The distinction in this specific example is probably not that significant. The with clause is sometimes necessary in more complicated queries.

Explicit joins may reference association or component/embedded attributes. In the case of component/embedded attributes, the join is logical and does not correlate to a physical (SQL) join.

12.8.6. About HQL Ordering

The results of the query can also be ordered. The ORDER BY clause is used to specify the selected values to be used to order the result. The types of expressions considered valid as part of the order-by clause include:

  • state fields
  • component/embeddable attributes
  • scalar expressions such as arithmetic operations, functions, etc.
  • identification variable declared in the select clause for any of the previous expression types

HQL does not mandate that all values referenced in the order-by clause must be named in the select clause, but it is required by JPQL. Applications desiring database portability should be aware that not all databases support referencing values in the order-by clause that are not referenced in the select clause.

Individual expressions in the order-by can be qualified with either ASC (ascending) or DESC (descending) to indicate the desired ordering direction.

Example. Order-by Examples

// legal because p.name is implicitly part of p
select p
from Person p
order by p.name

select c.id, sum( o.total ) as t
from Order o
    inner join o.customer c
group by c.id
order by t

12.8.7. About Bulk Update, Insert and Delete

Hibernate allows the use of Data Manipulation Language (DML) to bulk insert, update and delete data directly in the mapped database through the Hibernate Query Language.

Warning

Using DML may violate the object/relational mapping and may affect object state. Object state stays in memory and by using DML, the state of an in-memory object is not affected depending on the operation that is performed on the underlying database. In-memory data must be used with care if DML is used.

The pseudo-syntax for UPDATE and DELETE statements is:

( UPDATE | DELETE ) FROM? EntityName (WHERE where_conditions)?.

Note

The FROM keyword and the WHERE Clause are optional.

The result of execution of a UPDATE or DELETE statement is the number of rows that are actually affected (updated or deleted).

Example. Bulk Update Statement

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

String hqlUpdate = "update Company set name = :newName where name = :oldName";
int updatedEntities = s.createQuery( hqlUpdate )
        .setString( "newName", newName )
        .setString( "oldName", oldName )
        .executeUpdate();
tx.commit();
session.close();

Example. Bulk Delete Statement

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

String hqlDelete = "delete Company where name = :oldName";
int deletedEntities = s.createQuery( hqlDelete )
        .setString( "oldName", oldName )
        .executeUpdate();
tx.commit();
session.close();

The int value returned by the Query.executeUpdate() method indicates the number of entities within the database that were affected by the operation.

Internally, the database might use multiple SQL statements to execute the operation in response to a DML Update or Delete request. This might be because of relationships that exist between tables and the join tables that may need to be updated or deleted.

For example, issuing a delete statement (as in the example above) may actually result in deletes being executed against not just the Company table for companies that are named with oldName, but also against joined tables. Thus, a Company table in a BiDirectional ManyToMany relationship with an Employee table, would lose rows from the corresponding join table Company_Employee as a result of the successful execution of the previous example.

The int deletedEntries value above will contain a count of all the rows affected due to this operation, including the rows in the join tables.

The pseudo-syntax for INSERT statements is: INSERT INTO EntityName properties_list select_statement.

Note

Only the INSERT INTO …​ SELECT …​ form is supported; not the INSERT INTO …​ VALUES …​ form.

Example. Bulk Insert Statement

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();

String hqlInsert = "insert into Account (id, name) select c.id, c.name from Customer c where ...";
int createdEntities = s.createQuery( hqlInsert )
        .executeUpdate();
tx.commit();
session.close();

If you do not supply the value for the id attribute via the SELECT statement, an identifier is generated for you, as long as the underlying database supports auto-generated keys. The return value of this bulk insert operation is the number of entries actually created in the database.

12.8.8. About Collection Member References

References to collection-valued associations actually refer to the values of that collection.

Example. Collection References

select c
from Customer c
    join c.orders o
    join o.lineItems l
    join l.product p
where o.status = 'pending'
  and p.status = 'backorder'

// alternate syntax
select c
from Customer c,
    in(c.orders) o,
    in(o.lineItems) l
    join l.product p
where o.status = 'pending'
  and p.status = 'backorder'

In the example, the identification variable o actually refers to the object model type Order which is the type of the elements of the Customer#orders association.

The example also shows the alternate syntax for specifying collection association joins using the IN syntax. Both forms are equivalent. Which form an application chooses to use is simply a matter of taste.

12.8.9. About Qualified Path Expressions

It was previously stated that collection-valued associations actually refer to the values of that collection. Based on the type of collection, there are also available a set of explicit qualification expressions.

Table 12.22. Qualified Path Expressions

ExpressionDescription

VALUE

Refers to the collection value. Same as not specifying a qualifier. Useful to explicitly show intent. Valid for any type of collection-valued reference.

INDEX

According to HQL rules, this is valid for both Maps and Lists which specify a javax.persistence.OrderColumn annotation to refer to the Map key or the List position (aka the OrderColumn value). JPQL however, reserves this for use in the List case and adds KEY for the MAP case. Applications interested in JPA provider portability should be aware of this distinction.

KEY

Valid only for Maps. Refers to the map’s key. If the key is itself an entity, can be further navigated.

ENTRY

Only valid only for Maps. Refers to the Map’s logical java.util.Map.Entry tuple (the combination of its key and value). ENTRY is only valid as a terminal path and only valid in the select clause.

Example. Qualified Collection References

// Product.images is a Map<String,String> : key = a name, value = file path

// select all the image file paths (the map value) for Product#123
select i
from Product p
    join p.images i
where p.id = 123

// same as above
select value(i)
from Product p
    join p.images i
where p.id = 123

// select all the image names (the map key) for Product#123
select key(i)
from Product p
    join p.images i
where p.id = 123

// select all the image names and file paths (the 'Map.Entry') for Product#123
select entry(i)
from Product p
    join p.images i
where p.id = 123

// total the value of the initial line items for all orders for a customer
select sum( li.amount )
from Customer c
        join c.orders o
        join o.lineItems li
where c.id = 123
  and index(li) = 1

12.8.10. About Scalar Functions

HQL defines some standard functions that are available regardless of the underlying database in use. HQL can also understand additional functions defined by the dialect and the application.

12.8.11. About HQL Standardized Functions

The following functions are available in HQL regardless of the underlying database in use.

Table 12.23. HQL Standardized Functions

FunctionDescription

BIT_LENGTH

Returns the length of binary data.

CAST

Performs a SQL cast. The cast target should name the Hibernate mapping type to use.

EXTRACT

Performs a SQL extraction on datetime values. An extraction extracts parts of the datetime (the year, for example). See the abbreviated forms below.

SECOND

Abbreviated extract form for extracting the second.

MINUTE

Abbreviated extract form for extracting the minute.

HOUR

Abbreviated extract form for extracting the hour.

DAY

Abbreviated extract form for extracting the day.

MONTH

Abbreviated extract form for extracting the month.

YEAR

Abbreviated extract form for extracting the year.

STR

Abbreviated form for casting a value as character data.

Application developers can also supply their own set of functions. This would usually represent either custom SQL functions or aliases for snippets of SQL. Such function declarations are made by using the addSqlFunction method of org.hibernate.cfg.Configuration

12.8.12. About the Concatenation Operation

HQL defines a concatenation operator in addition to supporting the concatenation (CONCAT) function. This is not defined by JPQL, so portable applications should avoid using it. The concatenation operator is taken from the SQL concatenation operator - ||.

Example. Concatenation Operation Example

select 'Mr. ' || c.name.first || ' ' || c.name.last
from Customer c
where c.gender = Gender.MALE

12.8.13. About Dynamic Instantiation

There is a particular expression type that is only valid in the select clause. Hibernate calls this "dynamic instantiation". JPQL supports some of this feature and calls it a "constructor expression".

Example. Dynamic Instantiation Example - Constructor

select new Family( mother, mate, offspr )
from DomesticCat as mother
    join mother.mate as mate
    left join mother.kittens as offspr

So rather than dealing with the Object[] here we are wrapping the values in a type-safe java object that will be returned as the results of the query. The class reference must be fully qualified and it must have a matching constructor.

The class here need not be mapped. If it does represent an entity, the resulting instances are returned in the NEW state (not managed!).

This is the part JPQL supports as well. HQL supports additional "dynamic instantiation" features. First, the query can specify to return a List rather than an Object[] for scalar results:

Example. Dynamic Instantiation Example - List

select new list(mother, offspr, mate.name)
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

The results from this query will be a List<List> as opposed to a List<Object[]>

HQL also supports wrapping the scalar results in a Map.

Example. Dynamic Instantiation Example - Map

select new map( mother as mother, offspr as offspr, mate as mate )
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

select new map( max(c.bodyWeight) as max, min(c.bodyWeight) as min, count(*) as n )
from Cat cxt

The results from this query will be a List<Map<String,Object>> as opposed to a List<Object[]>. The keys of the map are defined by the aliases given to the select expressions.

12.8.14. About HQL Predicates

Predicates form the basis of the where clause, the having clause and searched case expressions. They are expressions which resolve to a truth value, generally TRUE or FALSE, although boolean comparisons involving NULL values generally resolve to UNKNOWN.

HQL Predicates
  • Null Predicate

    Check a value for null. Can be applied to basic attribute references, entity references and parameters. HQL additionally allows it to be applied to component/embeddable types.

    Null Check Examples

    // select everyone with an associated address
    select p
    from Person p
    where p.address is not null
    
    // select everyone without an associated address
    select p
    from Person p
      where p.address is null
  • Like Predicate

    Performs a like comparison on string values. The syntax is:

    like_expression ::=
           string_expression
           [NOT] LIKE pattern_value
           [ESCAPE escape_character]

    The semantics follow that of the SQL like expression. The pattern_value is the pattern to attempt to match in the string_expression. Just like SQL, pattern_value can use _ (underscore) and % (percent) as wildcards. The meanings are the same. The _ matches any single character. The % matches any number of characters.

    The optional escape_character is used to specify an escape character used to escape the special meaning of _ and % in the pattern_value. This is useful when needing to search on patterns including either _ or %.

    Like Predicate Examples

    select p
    from Person p
    where p.name like '%Schmidt'
    
    select p
    from Person p
    where p.name not like 'Jingleheimmer%'
    
    // find any with name starting with "sp_"
    select sp
    from StoredProcedureMetadata sp
    where sp.name like 'sp|_%' escape '|'
  • Between Predicate

    Analogous to the SQL BETWEEN expression. Perform an evaluation that a value is within the range of 2 other values. All the operands should have comparable types.

    Between Predicate Examples

    select p
    from Customer c
        join c.paymentHistory p
    where c.id = 123
      and index(p) between 0 and 9
    
    select c
    from Customer c
    where c.president.dateOfBirth
            between {d '1945-01-01'}
                and {d '1965-01-01'}
    
    select o
    from Order o
    where o.total between 500 and 5000
    
    select p
    from Person p
    where p.name between 'A' and 'E'
  • IN Predicate

    The IN predicate performs a check that a particular value is in a list of values. Its syntax is:

    in_expression ::= single_valued_expression
                [NOT] IN single_valued_list
    
    single_valued_list ::= constructor_expression |
                (subquery) |
                collection_valued_input_parameter
    
    constructor_expression ::= (expression[, expression]*)

    The types of the single_valued_expression and the individual values in the single_valued_list must be consistent. JPQL limits the valid types here to string, numeric, date, time, timestamp, and enum types. In JPQL, single_valued_expression can only refer to:

    • "state fields", which is its term for simple attributes. Specifically this excludes association and component/embedded attributes.
    • entity type expressions.

      In HQL, single_valued_expression can refer to a far more broad set of expression types. Single-valued association are allowed. So are component/embedded attributes, although that feature depends on the level of support for tuple or "row value constructor syntax" in the underlying database. Additionally, HQL does not limit the value type in any way, though application developers should be aware that different types may incur limited support based on the underlying database vendor. This is largely the reason for the JPQL limitations.

      The list of values can come from a number of different sources. In the constructor_expression and collection_valued_input_parameter, the list of values must not be empty; it must contain at least one value.

      In Predicate Examples

      select p
      from Payment p
      where type(p) in (CreditCardPayment, WireTransferPayment)
      
      select c
      from Customer c
      where c.hqAddress.state in ('TX', 'OK', 'LA', 'NM')
      
      select c
      from Customer c
      where c.hqAddress.state in ?
      
      select c
      from Customer c
      where c.hqAddress.state in (
          select dm.state
          from DeliveryMetadata dm
          where dm.salesTax is not null
      )
      
      // Not JPQL compliant!
      select c
      from Customer c
      where c.name in (
          ('John','Doe'),
          ('Jane','Doe')
      )
      
      // Not JPQL compliant!
      select c
      from Customer c
      where c.chiefExecutive in (
          select p
          from Person p
          where ...
      )

12.8.15. About Relational Comparisons

Comparisons involve one of the comparison operators - =, >, >=, <, ⇐, <>. HQL also defines != as a comparison operator synonymous with <>. The operands should be of the same type.

Example. Relational Comparison Examples

// numeric comparison
select c
from Customer c
where c.chiefExecutive.age < 30

// string comparison
select c
from Customer c
where c.name = 'Acme'

// datetime comparison
select c
from Customer c
where c.inceptionDate < {d '2000-01-01'}

// enum comparison
select c
from Customer c
where c.chiefExecutive.gender = com.acme.Gender.MALE

// boolean comparison
select c
from Customer c
where c.sendEmail = true

// entity type comparison
select p
from Payment p
where type(p) = WireTransferPayment

// entity value comparison
select c
from Customer c
where c.chiefExecutive = c.chiefTechnologist

Comparisons can also involve subquery qualifiers - ALL, ANY, SOME. SOME and ANY are synonymous.

The ALL qualifier resolves to true if the comparison is true for all of the values in the result of the subquery. It resolves to false if the subquery result is empty.

Example. ALL Subquery Comparison Qualifier Example

// select all players that scored at least 3 points
// in every game.
select p
from Player p
where 3 > all (
   select spg.points
   from StatsPerGame spg
   where spg.player = p
)

The ANY/SOME qualifier resolves to true if the comparison is true for some of (at least one of) the values in the result of the subquery. It resolves to false if the subquery result is empty.

12.9. Hibernate Services

12.9.1. About Hibernate Services

Services are classes that provide Hibernate with pluggable implementations of various types of functionality. Specifically they are implementations of certain service contract interfaces. The interface is known as the service role; the implementation class is know as the service implementation. Generally speaking, users can plug in alternate implementations of all standard service roles (overriding); they can also define additional services beyond the base set of service roles (extending).

12.9.2. About Service Contracts

The basic requirement for a service is to implement the marker interface org.hibernate.service.Service. Hibernate uses this internally for some basic type safety.

Optionally, the service can also implement the org.hibernate.service.spi.Startable and org.hibernate.service.spi.Stoppable interfaces to receive notifications of being started and stopped. Another optional service contract is org.hibernate.service.spi.Manageable which marks the service as manageable in JMX provided the JMX integration is enabled.

12.9.3. Types of Service Dependencies

Services are allowed to declare dependencies on other services using either of 2 approaches:

@org.hibernate.service.spi.InjectService
Any method on the service implementation class accepting a single parameter and annotated with @InjectService is considered requesting injection of another service.
By default the type of the method parameter is expected to be the service role to be injected. If the parameter type is different than the service role, the serviceRole attribute of the InjectService should be used to explicitly name the role.
By default injected services are considered required, that is the start up will fail if a named dependent service is missing. If the service to be injected is optional, the required attribute of the InjectService should be declared as false (default is true).
org.hibernate.service.spi.ServiceRegistryAwareService
The second approach is a pull approach where the service implements the optional service interface org.hibernate.service.spi.ServiceRegistryAwareService which declares a single injectServices method.
During startup, Hibernate will inject the org.hibernate.service.ServiceRegistry itself into services which implement this interface. The service can then use the ServiceRegistry reference to locate any additional services it needs.

12.9.4. The Service Registry

12.9.4.1. About the ServiceRegistry

The central service API, aside from the services themselves, is the org.hibernate.service.ServiceRegistry interface. The main purpose of a service registry is to hold, manage and provide access to services.

Service registries are hierarchical. Services in one registry can depend on and utilize services in that same registry as well as any parent registries.

Use org.hibernate.service.ServiceRegistryBuilder to build a org.hibernate.service.ServiceRegistry instance.

Example. Use ServiceRegistryBuilder to create a ServiceRegistry

ServiceRegistryBuilder registryBuilder = new ServiceRegistryBuilder( bootstrapServiceRegistry );
    ServiceRegistry serviceRegistry = registryBuilder.buildServiceRegistry();

12.9.5. Custom Services

12.9.5.1. About Custom Services

Once a org.hibernate.service.ServiceRegistry is built it is considered immutable; the services themselves might accept re-configuration, but immutability here means adding/replacing services. So another role provided by the org.hibernate.service.ServiceRegistryBuilder is to allow tweaking of the services that will be contained in the org.hibernate.service.ServiceRegistry generated from it.

There are two means to tell a org.hibernate.service.ServiceRegistryBuilder about custom services.

  • Implement a org.hibernate.service.spi.BasicServiceInitiator class to control on-demand construction of the service class and add it to the org.hibernate.service.ServiceRegistryBuilder via its addInitiator method.
  • Just instantiate the service class and add it to the org.hibernate.service.ServiceRegistryBuilder via its addService method.

Either approach the adding a service approach or the adding an initiator approach are valid for extending a registry (adding new service roles) and overriding services (replacing service implementations).

Example. Use ServiceRegistryBuilder to Replace an Existing Service with a Custom Service

   ServiceRegistryBuilder registryBuilder = new ServiceRegistryBuilder( bootstrapServiceRegistry );
   registryBuilder.addService( JdbcServices.class, new FakeJdbcService() );
   ServiceRegistry serviceRegistry = registryBuilder.buildServiceRegistry();


   public class FakeJdbcService implements JdbcServices{

       @Override
       public ConnectionProvider getConnectionProvider() {
           return null;
       }

       @Override
       public Dialect getDialect() {
           return null;
       }

       @Override
       public SqlStatementLogger getSqlStatementLogger() {
           return null;
       }

       @Override
       public SqlExceptionHelper getSqlExceptionHelper() {
           return null;
       }

       @Override
       public ExtractedDatabaseMetaData getExtractedMetaDataSupport() {
           return null;
       }

       @Override
       public LobCreator getLobCreator(LobCreationContext lobCreationContext) {
           return null;
       }

       @Override
       public ResultSetWrapper getResultSetWrapper() {
           return null;
       }
   }

12.9.6. The Boot-Strap Registry

12.9.6.1. About the Boot-strap Registry

The boot-strap registry holds services that absolutely have to be available for most things to work. The main service here is the ClassLoaderService which is a perfect example. Even resolving configuration files needs access to class loading services (resource look ups). This is the root registry (no parent) in normal use.

Instances of boot-strap registries are built using the org.hibernate.service.BootstrapServiceRegistryBuilder class.

12.9.6.2. Using BootstrapServiceRegistryBuilder

Example. Using BootstrapServiceRegistryBuilder

BootstrapServiceRegistry bootstrapServiceRegistry = new BootstrapServiceRegistryBuilder()
        // pass in org.hibernate.integrator.spi.Integrator instances which are not
        // auto-discovered (for whatever reason) but which should be included
        .with( anExplicitIntegrator )
        // pass in a class loader that Hibernate should use to load application classes
        .with( anExplicitClassLoaderForApplicationClasses )
        // pass in a class loader that Hibernate should use to load resources
        .with( anExplicitClassLoaderForResources )
        // see BootstrapServiceRegistryBuilder for rest of available methods
        ...
        // finally, build the bootstrap registry with all the above options
        .build();

12.9.6.3. BootstrapRegistry Services

org.hibernate.service.classloading.spi.ClassLoaderService

Hibernate needs to interact with class loaders. However, the manner in which Hibernate (or any library) should interact with class loaders varies based on the runtime environment which is hosting the application. Application servers, OSGi containers, and other modular class loading systems impose very specific class loading requirements. This service is provides Hibernate an abstraction from this environmental complexity. And just as importantly, it does so in a single-swappable-component manner.

In terms of interacting with a class loader, Hibernate needs the following capabilities:

  • the ability to locate application classes
  • the ability to locate integration classes
  • the ability to locate resources (properties files, xml files, etc)
  • the ability to load java.util.ServiceLoader
Note

Currently, the ability to load application classes and the ability to load integration classes are combined into a single "load class" capability on the service. That may change in a later release.

org.hibernate.integrator.spi.IntegratorService

Applications, add-ons and other modules need to integrate with Hibernate. The previous approach required a component, usually an application, to coordinate the registration of each individual module. This registration was conducted on behalf of each module’s integrator.

This service focuses on the discovery aspect. It leverages the standard Java java.util.ServiceLoader capability provided by the org.hibernate.service.classloading.spi.ClassLoaderService in order to discover implementations of the org.hibernate.integrator.spi.Integrator contract.

Integrators would simply define a file named /META-INF/services/org.hibernate.integrator.spi.Integrator and make it available on the class path.

This file is used by the java.util.ServiceLoader mechanism. It lists, one per line, the fully qualified names of classes which implement the org.hibernate.integrator.spi.Integrator interface.

12.9.7. The SessionFactory Registry

12.9.7.1. SessionFactory Registry

While it is best practice to treat instances of all the registry types as targeting a given org.hibernate.SessionFactory, the instances of services in this group explicitly belong to a single org.hibernate.SessionFactory.

The difference is a matter of timing in when they need to be initiated. Generally they need access to the org.hibernate.SessionFactory to be initiated. This special registry is org.hibernate.service.spi.SessionFactoryServiceRegistry

12.9.7.2. SessionFactory Services

org.hibernate.event.service.spi.EventListenerRegistry

Description
Service for managing event listeners.
Initiator
org.hibernate.event.service.internal.EventListenerServiceInitiator
Implementations
org.hibernate.event.service.internal.EventListenerRegistryImpl

12.9.8. Integrators

12.9.8.1. Integrators

The org.hibernate.integrator.spi.Integrator is intended to provide a simple means for allowing developers to hook into the process of building a functioning SessionFactory. The org.hibernate.integrator.spi.Integrator interface defines 2 methods of interest: integrate allows us to hook into the building process; disintegrate allows us to hook into a SessionFactory shutting down.

Note

There is a 3rd method defined on org.hibernate.integrator.spi.Integrator, an overloaded form of integrate accepting a org.hibernate.metamodel.source.MetadataImplementor instead of org.hibernate.cfg.Configuration. This form is intended for use with the new metamodel code scheduled for completion in 5.0.

In addition to the discovery approach provided by the IntegratorService, applications can manually register Integrator implementations when building the BootstrapServiceRegistry.

12.9.8.2. Integrator use-cases

The main use cases for an org.hibernate.integrator.spi.Integrator right now are registering event listeners and providing services (see org.hibernate.integrator.spi.ServiceContributingIntegrator). With 5.0 we plan on expanding that to allow altering the metamodel describing the mapping between object and relational models.

Example. Registering event listeners

public class MyIntegrator implements org.hibernate.integrator.spi.Integrator {

    public void integrate(
            Configuration configuration,
            SessionFactoryImplementor sessionFactory,
            SessionFactoryServiceRegistry serviceRegistry) {
        // As you might expect, an EventListenerRegistry is the thing with which event listeners are registered  It is a
        // service so we look it up using the service registry
        final EventListenerRegistry eventListenerRegistry = serviceRegistry.getService( EventListenerRegistry.class );

        // If you wish to have custom determination and handling of "duplicate" listeners, you would have to add an
        // implementation of the org.hibernate.event.service.spi.DuplicationStrategy contract like this
        eventListenerRegistry.addDuplicationStrategy( myDuplicationStrategy );

        // EventListenerRegistry defines 3 ways to register listeners:
        //     1) This form overrides any existing registrations with
        eventListenerRegistry.setListeners( EventType.AUTO_FLUSH, myCompleteSetOfListeners );
        //     2) This form adds the specified listener(s) to the beginning of the listener chain
        eventListenerRegistry.prependListeners( EventType.AUTO_FLUSH, myListenersToBeCalledFirst );
        //     3) This form adds the specified listener(s) to the end of the listener chain
        eventListenerRegistry.appendListeners( EventType.AUTO_FLUSH, myListenersToBeCalledLast );
    }
}

12.10. Envers

12.10.1. About Hibernate Envers

Hibernate Envers is an auditing and versioning system, providing JBoss EAP with a means to track historical changes to persistent classes. Audit tables are created for entities annotated with @Audited, which store the history of changes made to the entity. The data can then be retrieved and queried.

Envers allows developers to:

  • audit all mappings defined by the JPA specification,
  • audit all hibernate mappings that extend the JPA specification,
  • audit entities mapped by or using the native Hibernate API
  • log data for each revision using a revision entity, and
  • query historical data.

12.10.2. About Auditing Persistent Classes

Auditing of persistent classes is done in JBoss EAP through Hibernate Envers and the @Audited annotation. When the annotation is applied to a class, a table is created, which stores the revision history of the entity.

Each time a change is made to the class, an entry is added to the audit table. The entry contains the changes to the class, and is given a revision number. This means that changes can be rolled back, or previous revisions can be viewed.

12.10.3. Auditing Strategies

12.10.3.1. About Auditing Strategies

Auditing strategies define how audit information is persisted, queried and stored. There are currently two audit strategies available with Hibernate Envers:

Default Audit Strategy
  • This strategy persists the audit data together with a start revision. For each row that is inserted, updated or deleted in an audited table, one or more rows are inserted in the audit tables, along with the start revision of its validity.
  • Rows in the audit tables are never updated after insertion. Queries of audit information use subqueries to select the applicable rows in the audit tables, which are slow and difficult to index.
Validity Audit Strategy
  • This strategy stores the start revision, as well as the end revision of the audit information. For each row that is inserted, updated or deleted in an audited table, one or more rows are inserted in the audit tables, along with the start revision of its validity.
  • At the same time, the end revision field of the previous audit rows (if available) is set to this revision. Queries on the audit information can then use between start and end revision, instead of subqueries. This means that persisting audit information is a little slower because of the extra updates, but retrieving audit information is a lot faster.
  • This can also be improved by adding extra indexes.

For more information on auditing, refer to About Auditing Persistent Classes. To set the auditing strategy for the application, refer here: Set the Auditing Strategy .

12.10.3.2. Set the Auditing Strategy

There are two audit strategies supported by JBoss EAP:

  • The default audit strategy
  • The validity audit strategy
Define an Auditing Strategy

Configure the org.hibernate.envers.audit_strategy property in the persistence.xml file of the application. If the property is not set in the persistence.xml file, then the default audit strategy is used.

Set the Default Audit Strategy

<property name="org.hibernate.envers.audit_strategy" value="org.hibernate.envers.strategy.DefaultAuditStrategy"/>

Set the Validity Audit Strategy

<property name="org.hibernate.envers.audit_strategy" value="org.hibernate.envers.strategy.ValidityAuditStrategy"/>

12.10.4. Adding Auditing Support to a JPA Entity

JBoss EAP uses entity auditing, through About Hibernate Envers, to track the historical changes of a persistent class. This topic covers adding auditing support for a JPA entity.

Add Auditing Support to a JPA Entity

  1. Configure the available auditing parameters to suit the deployment: Configure Envers Parameters .
  2. Open the JPA entity to be audited.
  3. Import the org.hibernate.envers.Audited interface.
  4. Apply the @Audited annotation to each field or property to be audited, or apply it once to the whole class.

    Example: Audit Two Fields

    import org.hibernate.envers.Audited;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Column;
    
    @Entity
    public class Person {
        @Id
        @GeneratedValue
        private int id;
    
        @Audited
        private String name;
    
        private String surname;
    
        @ManyToOne
        @Audited
        private Address address;
    
        // add getters, setters, constructors, equals and hashCode here
    }

    Example: Audit an entire Class

    import org.hibernate.envers.Audited;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.GeneratedValue;
    import javax.persistence.Column;
    
    @Entity
    @Audited
    public class Person {
        @Id
        @GeneratedValue
        private int id;
    
        private String name;
    
        private String surname;
    
        @ManyToOne
        private Address address;
    
        // add getters, setters, constructors, equals and hashCode here
    }

Once the JPA entity has been configured for auditing, a table called _AUD will be created to store the historical changes.

12.10.5. Configuration

12.10.5.1. Configure Envers Parameters

JBoss EAP uses entity auditing, through Hibernate Envers, to track the historical changes of a persistent class.

Configuring the Available Envers Parameters

  1. Open the persistence.xml file for the application.
  2. Add, remove or configure Envers properties as required. For a list of available properties, refer to Envers Configuration Properties .

    Example: Envers Parameters

    <persistence-unit name="mypc">
      <description>Persistence Unit.</description>
      <jta-data-source>java:jboss/datasources/ExampleDS</jta-data-source>
      <shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>
      <properties>
        <property name="hibernate.hbm2ddl.auto" value="create-drop" />
        <property name="hibernate.show_sql" value="true" />
        <property name="hibernate.cache.use_second_level_cache" value="true" />
        <property name="hibernate.cache.use_query_cache" value="true" />
        <property name="hibernate.generate_statistics" value="true" />
        <property name="org.hibernate.envers.versionsTableSuffix" value="_V" />
        <property name="org.hibernate.envers.revisionFieldName" value="ver_rev" />
      </properties>
    </persistence-unit>

12.10.5.2. Enable or Disable Auditing at Runtime

Enable or Disable Entity Version Auditing at Runtime

  1. Subclass the AuditEventListener class.
  2. Override the following methods that are called on Hibernate events:

    • onPostInsert
    • onPostUpdate
    • onPostDelete
    • onPreUpdateCollection
    • onPreRemoveCollection
    • onPostRecreateCollection
  3. Specify the subclass as the listener for the events.
  4. Determine if the change should be audited.
  5. Pass the call to the superclass if the change should be audited.

12.10.5.3. Configure Conditional Auditing

Hibernate Envers persists audit data in reaction to various Hibernate events, using a series of event listeners. These listeners are registered automatically if the Envers jar is in the class path.

Implement Conditional Auditing

  1. Set the hibernate.listeners.envers.autoRegister Hibernate property to false in the persistence.xml file.
  2. Subclass each event listener to be overridden. Place the conditional auditing logic in the subclass, and call the super method if auditing should be performed.
  3. Create a custom implementation of org.hibernate.integrator.spi.Integrator, similar to org.hibernate.envers.event.EnversIntegrator. Use the event listener subclasses created in step two, rather than the default classes.
  4. Add a META-INF/services/org.hibernate.integrator.spi.Integrator file to the jar. This file should contain the fully qualified name of the class implementing the interface.

12.10.5.4. Envers Configuration Properties

Table 12.24. Entity Data Versioning Configuration Parameters

Property NameDefault ValueDescription

org.hibernate.envers.audit_table_prefix

It has is no default value

A string that is prepended to the name of an audited entity, to create the name of the entity that will hold the audit information.

org.hibernate.envers.audit_table_suffix

_AUD

A string that is appended to the name of an audited entity to create the name of the entity that will hold the audit information. For example, if an entity with a table name of Person is audited, Envers will generate a table called Person_AUD to store the historical data.

org.hibernate.envers.revision_field_name

REV

The name of the field in the audit entity that holds the revision number.

org.hibernate.envers.revision_type_field_name

REVTYPE

The name of the field in the audit entity that holds the type of revision. The current types of revisions possible are: add, mod and del for inserting, modifying or deleting respectively.

org.hibernate.envers.revision_on_collection_change

true

This property determines if a revision should be generated if a relation field that is not owned changes. This can either be a collection in a one-to-many relation, or the field using the mappedBy attribute in a one-to-one relation.

org.hibernate.envers.do_not_audit_optimistic_locking_field

true

When true, properties used for optimistic locking (annotated with @Version) will automatically be excluded from auditing.

org.hibernate.envers.store_data_at_delete

false

This property defines whether or not entity data should be stored in the revision when the entity is deleted, instead of only the ID, with all other properties marked as null. This is not usually necessary, as the data is present in the last-but-one revision. Sometimes, however, it is easier and more efficient to access it in the last revision. However, this means the data the entity contained before deletion is stored twice.

org.hibernate.envers.default_schema

null (same as normal tables)

The default schema name used for audit tables. Can be overridden using the @AuditTable(schema="…​") annotation. If not present, the schema will be the same as the schema of the normal tables.

org.hibernate.envers.default_catalog

null (same as normal tables)

The default catalog name that should be used for audit tables. Can be overridden using the @AuditTable(catalog="…​") annotation. If not present, the catalog will be the same as the catalog of the normal tables.

org.hibernate.envers.audit_strategy

org.hibernate.envers.strategy.DefaultAuditStrategy

This property defines the audit strategy that should be used when persisting audit data. By default, only the revision where an entity was modified is stored. Alternatively, org.hibernate.envers.strategy.ValidityAuditStrategy stores both the start revision and the end revision. Together, these define when an audit row was valid.

org.hibernate.envers.audit_strategy_validity_end_rev_field_name

REVEND

The column name that will hold the end revision number in audit entities. This property is only valid if the validity audit strategy is used.

org.hibernate.envers.audit_strategy_validity_store_revend_timestamp

false

This property defines whether the timestamp of the end revision, where the data was last valid, should be stored in addition to the end revision itself. This is useful to be able to purge old audit records out of a relational database by using table partitioning. Partitioning requires a column that exists within the table. This property is only evaluated if the ValidityAuditStrategy is used.

org.hibernate.envers.audit_strategy_validity_revend_timestamp_field_name

REVEND_TSTMP

Column name of the timestamp of the end revision at which point the data was still valid. Only used if the ValidityAuditStrategy is used, and org.hibernate.envers.audit_strategy_validity_store_revend_timestamp evaluates to true.

12.10.6. Retrieve Auditing Information through Queries

Hibernate Envers provides the functionality to retrieve audit information through queries.

Note

Queries on the audited data will be, in many cases, much slower than corresponding queries on live data, as they involve correlated subselects.

Querying for Entities of a Class at a Given Revision

The entry point for this type of query is:

AuditQuery query = getAuditReader()
    .createQuery()
    .forEntitiesAtRevision(MyEntity.class, revisionNumber);

Constraints can then be specified, using the AuditEntity factory class. The query below only selects entities where the name property is equal to John:

query.add(AuditEntity.property("name").eq("John"));

The queries below only select entities that are related to a given entity:

query.add(AuditEntity.property("address").eq(relatedEntityInstance));
// or
query.add(AuditEntity.relatedId("address").eq(relatedEntityId));

The results can then be ordered, limited, and have aggregations and projections (except grouping) set. The example below is a full query.

List personsAtAddress = getAuditReader().createQuery()
    .forEntitiesAtRevision(Person.class, 12)
    .addOrder(AuditEntity.property("surname").desc())
    .add(AuditEntity.relatedId("address").eq(addressId))
    .setFirstResult(4)
    .setMaxResults(2)
    .getResultList();

Query Revisions where Entities of a Given Class Changed

The entry point for this type of query is:

AuditQuery query = getAuditReader().createQuery()
    .forRevisionsOfEntity(MyEntity.class, false, true);

Constraints can be added to this query in the same way as the previous example. There are additional possibilities for this query:

AuditEntity.revisionNumber()
Specify constraints, projections and order on the revision number in which the audited entity was modified.
AuditEntity.revisionProperty(propertyName)
Specify constraints, projections and order on a property of the revision entity, corresponding to the revision in which the audited entity was modified.
AuditEntity.revisionType()
Provides accesses to the type of the revision (ADD, MOD, DEL).

The query results can then be adjusted as necessary. The query below selects the smallest revision number at which the entity of the MyEntity class, with the entityId ID has changed, after revision number 42:

Number revision = (Number) getAuditReader().createQuery()
    .forRevisionsOfEntity(MyEntity.class, false, true)
    .setProjection(AuditEntity.revisionNumber().min())
    .add(AuditEntity.id().eq(entityId))
    .add(AuditEntity.revisionNumber().gt(42))
    .getSingleResult();

Queries for revisions can also minimize/maximize a property. The query below selects the revision at which the value of the actualDate for a given entity was larger than a given value, but as small as possible:

Number revision = (Number) getAuditReader().createQuery()
    .forRevisionsOfEntity(MyEntity.class, false, true)
    // We are only interested in the first revision
    .setProjection(AuditEntity.revisionNumber().min())
    .add(AuditEntity.property("actualDate").minimize()
        .add(AuditEntity.property("actualDate").ge(givenDate))
        .add(AuditEntity.id().eq(givenEntityId)))
    .getSingleResult();

The minimize() and maximize() methods return a criteria, to which constraints can be added, which must be met by the entities with the maximized/minimized properties.

There are two boolean parameters passed when creating the query.

selectEntitiesOnly

This parameter is only valid when an explicit projection is not set.
If true, the result of the query will be a list of entities that changed at revisions satisfying the specified constraints.
If false, the result will be a list of three element arrays. The first element will be the changed entity instance. The second will be an entity containing revision data. If no custom entity is used, this will be an instance of DefaultRevisionEntity. The third element array will be the type of the revision (ADD, MOD, DEL).
selectDeletedEntities
This parameter specifies if revisions in which the entity was deleted must be included in the results. If true, the entities will have the revision type DEL, and all fields, except id, will have the value null.

Query Revisions of an Entity that Modified a Given Property

The query below will return all revisions of MyEntity with a given id, where the actualDate property has been changed.

AuditQuery query = getAuditReader().createQuery()
  .forRevisionsOfEntity(MyEntity.class, false, true)
  .add(AuditEntity.id().eq(id));
  .add(AuditEntity.property("actualDate").hasChanged())

The hasChanged condition can be combined with additional criteria. The query below will return a horizontal slice for MyEntity at the time the revisionNumber was generated. It will be limited to the revisions that modified prop1, but not prop2.

AuditQuery query = getAuditReader().createQuery()
  .forEntitiesAtRevision(MyEntity.class, revisionNumber)
  .add(AuditEntity.property("prop1").hasChanged())
  .add(AuditEntity.property("prop2").hasNotChanged());

The result set will also contain revisions with numbers lower than the revisionNumber. This means that this query cannot be read as "Return all MyEntities changed in revisionNumber with prop1 modified and prop2 untouched."

The query below shows how this result can be returned, using the forEntitiesModifiedAtRevision query:

AuditQuery query = getAuditReader().createQuery()
  .forEntitiesModifiedAtRevision(MyEntity.class, revisionNumber)
  .add(AuditEntity.property("prop1").hasChanged())
  .add(AuditEntity.property("prop2").hasNotChanged());

Query Entities Modified in a Given Revision

The example below shows the basic query for entities modified in a given revision. It allows entity names and corresponding Java classes changed in a specified revision to be retrieved:

Set<Pair<String, Class>> modifiedEntityTypes = getAuditReader()
    .getCrossTypeRevisionChangesReader().findEntityTypes(revisionNumber);

There are a number of other queries that are also accessible from org.hibernate.envers.CrossTypeRevisionChangesReader:

List<Object> findEntities(Number)
Returns snapshots of all audited entities changed (added, updated and removed) in a given revision. Executes n+1 SQL queries, where n is a number of different entity classes modified within the specified revision.
List<Object> findEntities(Number, RevisionType)
Returns snapshots of all audited entities changed (added, updated or removed) in a given revision filtered by modification type. Executes n+1 SQL queries, where n is a number of different entity classes modified within specified revision. Map<RevisionType, List<Object>>
findEntitiesGroupByRevisionType(Number)
Returns a map containing lists of entity snapshots grouped by modification operation (e.g. addition, update and removal). Executes 3n+1 SQL queries, where n is a number of different entity classes modified within specified revision.

12.11. Performance Tuning

12.11.1. Alternative Batch Loading Algorithms

Hibernate allows you to load data for associations using one of four fetching strategies: join, select, subselect and batch. Out of these four strategies, batch loading allows for the biggest performance gains as it is an optimization strategy for select fetching. In this strategy, Hibernate retrieves a batch of entity instances or collections in a single SELECT statement by specifying a list of primary or foreign keys. Batch fetching is an optimization of the lazy select fetching strategy.

There are two ways to configure batch fetching: per-class level or per-collection level.

  • Per-Class Level

    When Hibernate loads data on a per-class level, it requires the batch size of the association to pre-load when queried. For example, consider that at runtime you have 30 instances of a car object loaded in session. Each car object belongs to an owner object. If you were to iterate through all the car objects and request their owners, with lazy loading, Hibernate will issue 30 select statements - one for each owner. This is a performance bottleneck.

    You can instead, tell Hibernate to pre-load the data for the next batch of owners before they have been sought via a query. When an owner object has been queried, Hibernate will query many more of these objects in the same SELECT statement.

    The number of owner objects to query in advance depends upon the batch-size parameter specified at configuration time:

    <class name="owner" batch-size="10"></class>

    This tells Hibernate to query at least 10 more owner objects in expectation of them being needed in the near future. When a user queries the owner of car A, the owner of car B may already have been loaded as part of batch loading. When the user actually needs the owner of car B, instead of going to the database (and issuing a SELECT statement), the value can be retrieved from the current session.

    In addition to the batch-size parameter, Hibernate 4.2.0 has introduced a new configuration item to improve in batch loading performance. The configuration item is called Batch Fetch Style configuration and specified by the hibernate.batch_fetch_style parameter.

    Three different batch fetch styles are supported: LEGACY, PADDED and DYNAMIC. To specify which style to use, use org.hibernate.cfg.AvailableSettings#BATCH_FETCH_STYLE.

    • LEGACY: In the legacy style of loading, a set of pre-built batch sizes based on ArrayHelper.getBatchSizes(int) are utilized. Batches are loaded using the next-smaller pre-built batch size from the number of existing batchable identifiers.

      Continuing with the above example, with a batch-size setting of 30, the pre-built batch sizes would be [30, 15, 10, 9, 8, 7, .., 1]. An attempt to batch load 29 identifiers would result in batches of 15, 10, and 4. There will be 3 corresponding SQL queries, each loading 15, 10 and 4 owners from the database.

    • PADDED - Padded is similar to LEGACY style of batch loading. It still utilizes pre-built batch sizes, but uses the next-bigger batch size and pads the extra identifier placeholders.

      As with the example above, if 30 owner objects are to be initialized, there will only be one query executed against the database.

      However, if 29 owner objects are to be initialized, Hibernate will still execute only 1 SQL select statement of batch size 30, with the extra space padded with a repeated identifier.

    • Dynamic - While still conforming to batch-size restrictions, this style of batch loading dynamically builds its SQL SELECT statement using the actual number of objects to be loaded.

      For example, for 30 owner objects, and a maximum batch size of 30, a call to retrieve 30 owner objects will result in one SQL SELECT statement. A call to retrieve 35 will result in two SQL statements, of batch sizes 30 and 5 respectively. Hibernate will dynamically alter the second SQL statement to keep at 5, the required number, while still remaining under the restriction of 30 as the batch-size. This is different to the PADDED version, as the second SQL will not get PADDED, and unlike the LEGACY style, there is no fixed size for the second SQL statement - the second SQL is created dynamically.

      For a query of less than 30 identifiers, this style will dynamically only load the number of identifiers requested.

  • Per-Collection Level

    Hibernate can also batch load collections honoring the batch fetch size and styles as listed in the per-class section above.

    To reverse the example used in the previous section, consider that you need to load all the car objects owned by each owner object. If 10 owner objects are loaded in the current session iterating through all owners will generate 10 SELECT statements, one for every call to getCars() method. If you enable batch fetching for the cars collection in the mapping of Owner, Hibernate can pre-fetch these collections, as shown below.

    <class name="Owner"><set name="cars" batch-size="5"></set></class>

    Thus, with a batch-size of 5 and using legacy batch style to load 10 collections, Hibernate will execute two SELECT statements, each retrieving 5 collections.

12.11.2. Second Level Caching of Object References for Non-mutable Data

Hibernate automatically caches data within memory for improved performance. This is accomplished by an in-memory cache which reduces the number of times that database lookups are required, especially for data that rarely changes.

Hibernate maintains two types of caches. The primary cache (also called the first-level cache) is mandatory. This cache is associated with the current session and all requests must pass through it. The secondary cache (also called the second-level cache) is optional, and is only consulted after the primary cache has been consulted first.

Data is stored in the second-level cache by first disassembling it into a state array. This array is deep copied, and that deep copy is put into the cache. The reverse is done for reading from the cache. This works well for data that changes (mutable data), but is inefficient for immutable data.

Deep copying data is an expensive operation in terms of memory usage and processing speed. For large data sets, memory and processing speed become a performance-limiting factor. Hibernate allows you to specify that immutable data be referenced rather than copied. Instead of copying entire data sets, Hibernate can now store the reference to the data in the cache.

This can be done by changing the value of the configuration setting hibernate.cache.use_reference_entries to true. By default, hibernate.cache.use_reference_entries is set to false.

When hibernate.cache.use_reference_entries is set to true, an immutable data object that does not have any associations is not copied into the second-level cache, and only a reference to it is stored.

Warning

When hibernate.cache.use_reference_entries is set to true, immutable data objects with associations are still deep copied into the second-level cache.