Chapter 2. Getting started with rules

You can get started creating custom MTA rules by creating a rule or by reviewing the quickstarts.

2.1. Creating your first XML rule

This section guides you through the process of creating and testing your first MTA XML-based rule. This assumes that you have already installed MTA. See the CLI Guide for installation instructions.

In this example, you will write a rule to discover instances where an application defines a jboss-web.xml file containing a <class-loading> element and provide a link to the documentation that describes how to migrate the code.

Creating the directory structure for the rule

Create a directory structure to contain your first rule and the data file to use for testing. 

$ mkdir -p /home/<USER_NAME>/migration-rules/rules
$ mkdir -p /home/<USER_NAME>/migration-rules/data

This directory structure will also be used to hold the generated MTA reports.

Creating data to test the rule

  1. Create a jboss-web.xml file in the /home/<USER_NAME>/migration-rules/data/ subdirectory.

  2. Copy in the following content. 

    <!DOCTYPE jboss-web PUBLIC "-//JBoss//DTD Web Application 4.2//EN" "http://www.jboss.org/j2ee/dtd/jboss-web_4_2.dtd">
<jboss-web>
    <class-loading java2ClassLoadingCompliance="false">
        <loader-repository>
            seam.jboss.org:loader=@projectName@
            <loader-repository-config>java2ParentDelegation=false</loader-repository-config>
        </loader-repository>
    </class-loading>
</jboss-web>

Creating the rule

MTA XML-based rules use the following rule pattern: 

when(condition)
  perform(action)
otherwise(action)

Procedure

  1. In the /home/<USER_NAME>/migration-rules/rules/ directory, create a file named JBoss5-web-class-loading.windup.xml that contains the following content: 

    <?xml version="1.0"?>
<ruleset id="<UNIQUE_RULESET_ID>"
  xmlns="http://windup.jboss.org/schema/jboss-ruleset"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://windup.jboss.org/schema/jboss-ruleset http://windup.jboss.org/schema/jboss-ruleset/windup-jboss-ruleset.xsd">
  <metadata>
      <description>
          <!-- Ruleset Description -->
      </description>
      <dependencies>
          <!-- Ruleset Dependencies -->
      </dependencies>
      <sourceTechnology id="<SOURCE_ID>" versionRange="<SOURCE_VERSION_RANGE>"/>
      <targetTechnology id="<TARGET_ID>" versionRange="<TARGET_VERSION_RANGE>"/>
      <tag>Reviewed-2015-05-01</tag>
  </metadata>
  <rules>
      <rule id="<UNIQUE_RULE_ID>">
        <when>
            <!-- Test for a condition here -->
        </when>
        <perform>
            <!-- Perform an action -->
        </perform>
      </rule>
   </rules>
</ruleset>
    Note

    The XML file name must include the .windup.xml or .mta.xml extension. Otherwise, MTA does not evaluate the new rule.

  2. Add a unique identifier for the ruleset and rule:

    • Replace <UNIQUE_RULESET_ID> with an appropriate ruleset ID, for example, JBoss5-web-class-loading.
    • Replace <UNIQUE_RULE_ID> with an appropriate rule ID, for example, JBoss5-web-class-loading_001.

  3. Add the following ruleset add-on dependencies: 

    <dependencies>
  <addon id="org.jboss.windup.rules,windup-rules-javaee,3.0.0.Final"/>
  <addon id="org.jboss.windup.rules,windup-rules-java,3.0.0.Final"/>
</dependencies>

  4. Add the source and target technologies:

    • Replace <SOURCE_ID> with eap.
    • Replace <TARGET_ID> with eap.

  5. Set the source and target technology versions.

    • Replace <SOURCE_VERSION_RANGE> with (4,5).
    • Replace <TARGET_VERSION_RANGE> with (6,).

    See the Apache Maven version range specification for more information.

  6. Complete the when condition. Because this rule tests for a match in an XML file, xmlfile is used to evaluate the files.

    To match on the class-loading element that is a child of jboss-web, use the xpath expression jboss-web/class-loading. 

    <when>
    <xmlfile matches="jboss-web/class-loading" />
</when>

  7. Complete the perform action for this rule.

    • Add a classification with a descriptive title and a level of effort of 1.

    • Provide a hint with an informative message and a link to documentation that describes the migration details. 

      <perform>
    <iteration>
        <classification title="JBoss Web Application Descriptor" effort="1"/>
        <hint title="JBoss Web XML class-loading element is no longer valid">
          <message>
            The class-loading element is no longer valid in the jboss-web.xml file.
          </message>
          <link href="https://access.redhat.com/documentation/en-US/JBoss_Enterprise_Application_Platform/6.4/html-single/Migration_Guide/index.html#Create_or_Modify_Files_That_Control_Class_Loading_in_JBoss_Enterprise_Application_Platform_6" title="Create or Modify Files That Control Class Loading in JBoss EAP 6"/>
        </hint>
    </iteration>
</perform>

The rule is now complete and should look like the following example. 

<?xml version="1.0"?>
<ruleset id="JBoss5-web-class-loading"
    xmlns="http://windup.jboss.org/schema/jboss-ruleset"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://windup.jboss.org/schema/jboss-ruleset http://windup.jboss.org/schema/jboss-ruleset/windup-jboss-ruleset.xsd">
    <metadata>
        <description>
            This ruleset looks for the class-loading element in a jboss-web.xml file, which is no longer valid in JBoss EAP 6
        </description>
         <dependencies>
            <addon id="org.jboss.windup.rules,windup-rules-javaee,3.0.0.Final"/>
            <addon id="org.jboss.windup.rules,windup-rules-java,3.0.0.Final"/>
        </dependencies>
        <sourceTechnology id="eap" versionRange="(4,5)"/>
        <targetTechnology id="eap" versionRange="[6,)"/>
    </metadata>
    <rules>
        <rule id="JBoss5-web-class-loading_001">
            <when>
                <xmlfile matches="jboss-web/class-loading" />
            </when>
            <perform>
                <iteration>
                    <classification title="JBoss Web Application Descriptor" effort="1"/>
                    <hint title="JBoss Web XML class-loading element is no longer valid">
                      <message>
                        The class-loading element is no longer valid in the jboss-web.xml file.
                      </message>
                      <link href="https://access.redhat.com/documentation/en-US/JBoss_Enterprise_Application_Platform/6.4/html-single/Migration_Guide/index.html#Create_or_Modify_Files_That_Control_Class_Loading_in_JBoss_Enterprise_Application_Platform_6" title="Create or modify files that control class loading in JBoss EAP 6"/>
                    </hint>
                </iteration>
            </perform>
        </rule>
     </rules>
</ruleset>

Installing the rule

An MTA rule is installed by placing the rule into the appropriate directory.

Copy the JBoss5-web-class-loading.windup.xml file to the <MTA_HOME>/rules/ directory. 

$ cp /home/<USER_NAME>/migration-rules/rules/JBoss5-web-class-loading.windup.xml <MTA_HOME>/rules/

Testing the rule

Open a terminal and execute the following command, passing the test file as an input argument and a directory for the output report. 

$ <MTA_HOME>/bin/mta-cli --sourceMode --input /home/<USER_NAME>/migration-rules/data --output /home/<USER_NAME>/migration-rules/reports --target eap:6

You should see the following result. 

Report created: /home/<USER_NAME>/migration-rules/reports/index.html
              Access it at this URL: file:///home/<USER_NAME>/migration-rules/reports/index.html

Reviewing the reports

Review the report to be sure that it provides the expected results. For a more detailed walkthrough of MTA reports, see the Review the reports section of the MTA CLI Guide.

  1. Open /home/<USER_NAME>/migration-rules/reports/index.html in a web browser.

  2. Verify that the rule executed.

    1. From the main landing page, click the Rule providers execution overview link to open the Rule Providers Execution Overview.

    2. Find the JBoss5-web-class-loading_001 rule and verify that its Status? is Condition met and its Result? is success.

      Figure 2.1. Test rule execution

      Test rule execution

  3. Verify that the rule matches the test data:

    1. From the main landing page, click the name of the application or input folder, which is data in this example.
    2. Click the Application Details report link.

    3. Click the jboss-web.xml link to view the Source Report.

      You can see that the <class-loading> line is highlighted, and the hint from the custom rule is shown inline.

      Figure 2.2. Rule match

      Rule match

      The top of the file lists the classifications for matching rules. You can use the link icon to view the details for that rule. Notice that in this example, the jboss-web.xml file matched on another rule (JBoss web application descriptor (jboss-web.xml)) that produced 1 story point. This, combined with the 1 story point from our custom rule, brings the total story points for this file to 2.

2.2. Reviewing the Migration Toolkit for Applications quickstarts

The Migration Toolkit for Applications quickstarts provide working examples of how to create custom Java-based rule add-ons and XML rules. You can use them as a starting point for creating your own custom rules.

Each quickstart has a README.adoc file that contains instructions for that quickstart.

You can download a Zip archive file of the latest version of the quickstarts. If you prefer to work with the source code, you can fork and clone the windup-quickstarts project repository.

Downloading the latest quickstart

You can download the latest release of a quickstart.

Procedure

  1. Launch a browser and navigate to https://github.com/windup/windup-quickstarts/releases.
  2. Click the latest release to download the Zip archive file to your local file system.

  3. Extract the archive files to a local directory.

    You can review the quickstart README.adoc file.

Forking and cloning the quickstart GitHub project

You can fork and clone the Quickstart Github project on your local machine.

Prerequisites

  • You must have git client installed.

Procedure

  1. Click Fork on the Migration Toolkit for Applications quickstart GitHub page to create the project in your own Git. The forked GitHub repository URL should look like this: https://github.com/<YOUR_USER_NAME>/windup-quickstarts.git.

  2. Clone the Migration Toolkit for Applications quickstart repository to your local file system: 

    $ git clone https://github.com/<YOUR_USER_NAME>/windup-quickstarts.git

    This creates a windup-quickstarts directory on your local file system.

  3. Navigate to the newly created directory: 

    $ cd windup-quickstarts/

  4. To retrieve the latest code updates, add the remote upstream repository so that you can fetch changes to the original forked repository: 

    $ git remote add upstream https://github.com/windup/windup-quickstarts.git

  5. Download the latest files from the upstream repository: 

    $ git fetch upstream