Chapter 28. Developing a Consumer From a WSDL Contract

Abstract

One way of creating a consumer is to start from a WSDL contract. The contract defines the operations, messages, and transport details of the service on which a consumer makes requests. The starting point code for the consumer is generated from the WSDL contract. The functionality required by the consumer is added to the generated code.

28.1. Generating the Stub Code

Overview

The cxf-codegen-plugin Maven plug-in generates the stub code from the WSDL contract. The stub code provides the supporting code that is required to invoke operations on the remote service.

For consumers, the cxf-codegen-plugin Maven plug-in generates the following types of code:

  • Stub code — Supporting files for implementing a consumer.
  • Starting point code — Sample code that connects to the remote service and invokes every operation on the remote service.

Generating the consumer code

To generate consumer code use the cxf-codegen-plugin Maven plug-in. Example 28.1, “Consumer Code Generation” shows how to use the code generator to generate consumer code.

Example 28.1. Consumer Code Generation

<plugin>
  <groupId>org.apache.cxf</groupId>
  <artifactId>cxf-codegen-plugin</artifactId>
  <version>${cxf.version}</version>
  <executions>
    <execution>
      <id>generate-sources</id>
      <phase>generate-sources</phase>
      <configuration>
        <sourceRoot>outputDir</sourceRoot>
        <wsdlOptions>
          <wsdlOption>
            <wsdl>wsdl</wsdl>
            <extraargs>
              <extraarg>-client</extraarg>
            </extraargs>
          </wsdlOption>
        </wsdlOptions>
      </configuration>
      <goals>
        <goal>wsdl2java</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Where outputDir is the location of a directory where the generated files are placed and wsdl specifies the WSDL contract’s location. The -client option generates starting point code for the consumer’s main() method.

For a complete list of the arguments available for the cxf-codegen-plugin Maven plug-in see Section 44.2, “cxf-codegen-plugin”.

Generated code

The code generation plug-in generates the following Java packages for the contract shown in Example 26.1, “HelloWorld WSDL Contract”:

  • org.apache.hello_world_soap_http — This package is generated from the http://apache.org/hello_world_soap_http target namespace. All of the WSDL entities defined in this namespace (for example, the Greeter port type and the SOAPService service) map to Java classes this Java package.
  • org.apache.hello_world_soap_http.types — This package is generated from the http://apache.org/hello_world_soap_http/types target namespace. All of the XML types defined in this namespace (that is, everything defined in the wsdl:types element of the HelloWorld contract) map to Java classes in this Java package.

The stub files generated by the cxf-codegen-plugin Maven plug-in fall into the following categories:

  • Classes representing WSDL entities in the org.apache.hello_world_soap_http package. The following classes are generated to represent WSDL entities:

    • Greeter — A Java interface that represents the Greeter wsdl:portType element. In JAX-WS terminology, this Java interface is the service endpoint interface (SEI).
    • SOAPService — A Java service class (extending javax.xml.ws.Service) that represents the SOAPService wsdl:service element.
    • PingMeFault — A Java exception class (extending java.lang.Exception) that represents the pingMeFault wsdl:fault element.
  • Classes representing XML types in the org.objectweb.hello_world_soap_http.types package. In the HelloWorld example, the only generated types are the various wrappers for the request and reply messages. Some of these data types are useful for the asynchronous invocation model.

28.2. Implementing a Consumer

Overview

To implement a consumer when starting from a WSDL contract, you must use the following stubs:

  • Service class
  • SEI

Using these stubs, the consumer code instantiates a service proxy to make requests on the remote service. It also implements the consumer’s business logic.

Generated service class

Example 28.2, “Outline of a Generated Service Class” shows the typical outline of a generated service class, ServiceName_Service[2], which extends the javax.xml.ws.Service base class.

Example 28.2. Outline of a Generated Service Class

@WebServiceClient(name="..." targetNamespace="..."
                  wsdlLocation="...")
public class ServiceName extends javax.xml.ws.Service
{
  ...
  public ServiceName(URL wsdlLocation, QName serviceName) { }

  public ServiceName() { }

  // Available only if you specify '-fe cxf' option in wsdl2java
  public ServiceName(Bus bus) { }

  @WebEndpoint(name="...")
  public SEI getPortName() { }
  .
  .
  .
}

The ServiceName class in Example 28.2, “Outline of a Generated Service Class” defines the following methods:

  • ServiceName(URL wsdlLocation, QName serviceName) — Constructs a service object based on the data in the wsdl:service element with the QName ServiceName service in the WSDL contract that is obtainable from wsdlLocation.
  • ServiceName() — The default constructor. It constructs a service object based on the service name and the WSDL contract that were provided at the time the stub code was generated (for example, when running the wsdl2java tool). Using this constructor presupposes that the WSDL contract remains available at a specified location.
  • ServiceName(Bus bus)(CXF specific) An additional constructor that enables you to specify the Bus instance used to configure the Service. This can be useful in the context of a multi-threaded application, where multiple Bus instances can be associated with different threads. This constructor provides a simple way of ensuring that the Bus that you specify is the one that is used with this Service. Only available if you specify the -fe cxf option when invoking the wsdl2java tool.
  • getPortName() — Returns a proxy for the endpoint defined by the wsdl:port element with the name attribute equal to PortName. A getter method is generated for every wsdl:port element defined by the ServiceName service. A wsdl:service element that contains multiple endpoint definitions results in a generated service class with multiple getPortName() methods.

Service endpoint interface

For every interface defined in the original WSDL contract, you can generate a corresponding SEI. A service endpoint interface is the Java mapping of a wsdl:portType element. Each operation defined in the original wsdl:portType element maps to a corresponding method in the SEI. The operation’s parameters are mapped as follows: . The input parameters are mapped to method arguments.

  1. The first output parameter is mapped to a return value.
  2. If there is more than one output parameter, the second and subsequent output parameters map to method arguments (moreover, the values of these arguments must be passed using Holder types).

For example, Example 28.3, “The Greeter Service Endpoint Interface” shows the Greeter SEI, which is generated from the wsdl:portType element defined in Example 26.1, “HelloWorld WSDL Contract”. For simplicity, Example 28.3, “The Greeter Service Endpoint Interface” omits the standard JAXB and JAX-WS annotations.

Example 28.3. The Greeter Service Endpoint Interface

package org.apache.hello_world_soap_http;
  ...
public interface Greeter
{
  public String sayHi();
  public String greetMe(String requestType);
  public void greetMeOneWay(String requestType);
  public void pingMe() throws PingMeFault;
}

Consumer main function

Example 28.4, “Consumer Implementation Code” shows the code that implements the HelloWorld consumer. The consumer connects to the SoapPort port on the SOAPService service and then proceeds to invoke each of the operations supported by the Greeter port type.

Example 28.4. Consumer Implementation Code

package demo.hw.client;

import java.io.File;
import java.net.URL;
import javax.xml.namespace.QName;
import org.apache.hello_world_soap_http.Greeter;
import org.apache.hello_world_soap_http.PingMeFault;
import org.apache.hello_world_soap_http.SOAPService;

public final class Client {

  private static final QName SERVICE_NAME =
  new QName("http://apache.org/hello_world_soap_http",
            "SOAPService");

  private Client()
  {
  }

  public static void main(String args[]) throws Exception
  {
 if (args.length == 0)
    {
      System.out.println("please specify wsdl");
      System.exit(1);
    }

 URL wsdlURL;
    File wsdlFile = new File(args[0]);
    if (wsdlFile.exists())
    {
      wsdlURL = wsdlFile.toURL();
    }
    else
    {
      wsdlURL = new URL(args[0]);
    }

    System.out.println(wsdlURL);
 SOAPService ss = new SOAPService(wsdlURL,SERVICE_NAME);
 Greeter port = ss.getSoapPort();
    String resp;

 System.out.println("Invoking sayHi...");
    resp = port.sayHi();
    System.out.println("Server responded with: " + resp);
    System.out.println();

    System.out.println("Invoking greetMe...");
    resp = port.greetMe(System.getProperty("user.name"));
    System.out.println("Server responded with: " + resp);
    System.out.println();

    System.out.println("Invoking greetMeOneWay...");
    port.greetMeOneWay(System.getProperty("user.name"));
    System.out.println("No response from server as method is OneWay");
    System.out.println();

 try {
      System.out.println("Invoking pingMe, expecting exception...");
      port.pingMe();
    } catch (PingMeFault ex) {
      System.out.println("Expected exception: PingMeFault has occurred.");
      System.out.println(ex.toString());
    }
    System.exit(0);
  }
}

The Client.main() method from Example 28.4, “Consumer Implementation Code” proceeds as follows:

Provided that the Apache CXF runtime classes are on your classpath, the runtime is implicitly initialized. There is no need to call a special function to initialize Apache CXF.

The consumer expects a single string argument that gives the location of the WSDL contract for HelloWorld. The WSDL contract’s location is stored in wsdlURL.

You create a service object using the constructor that requires the WSDL contract’s location and service name. Call the appropriate getPortName() method to obtain an instance of the required port. In this case, the SOAPService service supports only the SoapPort port, which implements the Greeter service endpoint interface.

The consumer invokes each of the methods supported by the Greeter service endpoint interface.

In the case of the pingMe() method, the example code shows how to catch the PingMeFault fault exception.

Client proxy generated with -fe cxf option

If you generate your client proxy by specifying the -fe cxf option in wsdl2java (thereby selecting the cxf frontend), the generated client proxy code is better integrated with Java 7. In this case, when you call a getServiceNamePort() method, you get back a type that is a sub-interface of the SEI and implements the following additional interfaces:

  • java.lang.AutoCloseable
  • javax.xml.ws.BindingProvider (JAX-WS 2.0)
  • org.apache.cxf.endpoint.Client

To see how this simplifies working with a client proxy, consider the following Java code sample, written using a standard JAX-WS proxy object:

// Programming with standard JAX-WS proxy object
//
(ServiceNamePortType port = service.getServiceNamePort();
((BindingProvider)port).getRequestContext()
        .put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, address);
port.serviceMethod(...);
((Closeable)port).close();

And compare the preceding code with the following equivalent code sample, written using code generated by the cxf frontend:

// Programming with proxy generated using '-fe cxf' option
//
try (ServiceNamePortTypeProxy port = service.getServiceNamePort()) {
    port.getRequestContext().put(BindingProvider.ENDPOINT_ADDRESS_PROPERTY, address);
    port.serviceMethod(...);
}


[2] If the name attribute of the wsdl:service element ends in Service the _Service is not used.