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Implement dynamic JAX-WS web services clients

We can develop dynamic web services clients based on the Web Services for Java Platform, Enterprise Edition (Java EE) specification and the JAX-WS programming model.

IBM WebSphere Application Server supports JAX-WS and JAX-RPC. JAX-WS is the next generation web services programming model extending the foundation provided by JAX-RPC. Using the strategic JAX-WS programming model, development of web services and clients is simplified through support of a standards-based annotations model. Although JAX-RPC and applications are still supported, take advantage of the easy-to-implement JAX-WS programming model to develop new web services applications and clients.bprac

Develop web services clients based on the JAX-WS programming model

Web services clients that can both access and invoke JAX-WS web services are developed based on the Web Services for Java EE specification. The application server supports EJB clients, Java EE application clients, JSP files and servlets that are based on JAX-WS. Web services clients based on the JAX-RPC specification can invoke JAX-WS based web services if the WSDL file complies with the Web Services-Interoperability (WS-I) Basic Profile.

The JAX-WS client programming model supports both the Dispatch client API and the dynamic proxy client API. The Dispatch client API is a dynamic client programming model, whereas the static client programming model for JAX-WS is the dynamic proxy client. The Dispatch and dynamic proxy clients enable both synchronous and asynchronous invocation of JAX-WS web services.

The Dispatch client API, javax.xml.ws.Dispatch, is an XML messaging-oriented client intended for advanced XML developers who prefer using XML constructs. The Dispatch API can send data in either PAYLOAD or MESSAGE mode. When using the PAYLOAD mode, the Dispatch client is only responsible for providing the contents of the soap:Body and JAX-WS includes the payload in a soap:Envelope element. When using the MESSAGE mode, the Dispatch client is responsible for providing the entire SOAP envelope. You do not need a WSDL file if we are developing a dynamic client.

In contrast, the dynamic proxy client invokes a web service based on a service endpoint interface (SEI) provided. The JAX-WS dynamic proxy instances leverage the dynamic proxy function in the base Java SE Runtime Environment (JRE) 6.

To develop web services clients based on JAX-WS, we must determine the client model that best suits the needs of our web service application. To work directly with XML rather than a Java abstraction and work with either the message structure or the message payload structure, use the Dispatch API to develop a dynamic web services client. However, if we want the Web services client to invoke the service based on service endpoint interfaces with a dynamic proxy, use the Dynamic Proxy API to develop a static web service client. Read about implementing static JAX-WS web services clients to learn how to develop static web services clients.

Complete this task to develop a dynamic web services client using the Dispatch API.

To invoke web services asynchronously using a static or dynamic JAX-WS client, determine to implement the callback or the polling model. Read about invoking JAX-WS web services asynchronously for more information regarding implementing asynchronous callback or polling for web service clients. The JAX-WS programming model for the service and client uses annotations to represent the same information that was provided in JAX-RPC client binding in a vendor-neutral manner.

Managed and unmanaged JAX-WS web services clients

The application server supports both managed and unmanaged web services clients when using JAX-WS:

  • Managed clients

    Web services for Java EE clients are defined by Java Specification Requirements (JSR) 109 and are managed clients because they run in a Java EE container. These clients are packaged as EAR files and contain components that act as service requesters. These components are comprised of a Java EE client application, a web component such as a servlet or JSP, or a session EJB. Web services managed clients use JSR 109 APIs and deployment information to look up and invoke a web service.

    For the managed clients, we can use JNDI look up to perform service lookup, or we can use annotations to inject instances of a JAX-WS service or port. Read about setting up UserName token Web Services Security, digital signature Web Services Security and Lightweight Third-Party Authentication (LTPA) token Web Services Security. The following code is an example of a context lookup that is JSR 109 compliant:

    InitialContext ctx = new InitialContext();
    FredsBankService service
=(FredsBankService)ctx.lookup("java:comp/env/service/FredsBankService");
    FredsBank fredsBank = service.getFredsBankPort();
    long balance = fredsBank.getBalance();

    Use the @WebServiceRef or @Resource annotation to declare managed clients. The usage of these annotations results in the type specified by the annotation being bound into the JNDI namespace. When the annotations are used on a field or method, they also result in injection of a JAX-WS service or port instance. You can use these annotations instead of declaring service-ref entries in the client deployment descriptor. We can still use the client deployment descriptor to declare JAX-WS managed clients, similar to JAX-RPC managed clients. We can also use the deployment descriptor to override and augment the information specified by @WebServiceRef and @Resource annotations. Use the @WebServiceRef annotation to bind and inject a JAX-WS service or port instance. We can only use the @Resource annotation to bind and inject a JAX-WS service instance. The use of either of these annotations to declare JAX-WS managed clients is only supported in certain class types. Some of these class types include JAX-WS endpoint implementation classes, JAX-WS handler classes, enterprise bean classes, and servlet classes.

    The following example uses the @WebServiceRef annotation to obtain an instance of FredsBank: 

    @WebServiceRef(name="service/FredsBankPort", value=FredsBankService.class)
FredsBank fredsBank;
    Now within the class, the fredsBank field does not have to be initialized. Use this field directly: 
    long balance = fredsBank.getBalance();

    We can also use the @WebServiceRef annotation to obtain instances of JAX-WS service classes; for example: 

    @WebServiceRef(name="service/FredsBankService")
FredsBankService service;

    Now within the class, the service field does not have to be initialized. Use this field directly: 

     FredsBank fredsBank = service.getFredsBankPort(); long balance = fredsBank.getBalance();

    In addition to the @WebServiceRef annotation, we can use the @Resource annotation to obtain an instance of JAX-WS service classes; for example: 

    @Resource(name="service/FredsBankService", type=FredsBankService.class)
FredsBankService service;

    As with the @WebServiceRef annotation, we can now use the service field without instantiation; for example: 

    FredsBank fredsBank = service.getFredsBankPort(); long balance = fredsBank.getBalance();

    Use the @Resource or @WebServiceRef annotations on a class. In this case, JNDI must be used to lookup the JAX-WS service or port; for example: 

    @WebServiceRef(name="service/FredsBankService", type=FredsBankService")
public class J2EEClientExample {
		…
		…

		public static void main(String[] args) {
			…
			…
		InitialContext ctx = new InitialContext();
FredsBankService service =(FredsBankService)ctx.lookup("java:comp/env/service/FredsBankService");
    	FredsBank fredsBank = service.getFredsBankPort();
    	long balance = fredsBank.getBalance();  

	}
	…
}

    For more information on using the @WebServiceRef and @Resource annotations, see the specifications for JSR-109, JSR-224, JSR-250, and Java Platform Enterprise Edition 5 (Java EE 5).

    As mentioned previously, when using annotations or JNDI to obtain instances of JAX-WS services and ports, do not instantiate the returned objects. Doing so results in an unmanaged client instance.

    Example of incorrect usage:

      @WebServiceRef(name="service/FredsBankService") FredsBankService service;
      service = new FredsBankService(); // client becomes unmanaged.

    For JAX-WS managed clients that are declared by the @WebServiceRef or @Resource annotation and for clients that are declared using service-ref entries in the client deployment descriptor, we can use the administrative console to supply the endpoint URL that the client uses. This specified URL overrides the endpoint URL in the WSDL document used by the client. To learn more about specifying this endpoint URL, see the configuring web services client bindings documentation.

  • Unmanaged clients

    Java Platform, Standard Edition (Java SE 6) clients that use the JAX-WS runtime environment to invoke web services and do not run in any Java EE container are known as unmanaged clients. A web services unmanaged client is a stand-alone Java client that can directly inspect a WSDL file and formulate the calls to the web service using JAX-WS APIs. These clients are packaged as JAR files, which do not contain any deployment information.

Starting with WebSphere Application Server v7.0 and later, Java EE 5 application modules (web application modules version 2.5 or above, or EJB modules version 3.0 or above) are scanned for annotations to identify JAX-WS services and clients. However, pre-Java EE 5 application modules (web application modules version 2.4 or before, or EJB modules version 2.1 or before) are not scanned for JAX-WS annotations, by default, for performance considerations. In the v6.1 Feature Pack for Web Services, the default behavior is to scan pre-Java EE 5 web application modules to identify JAX-WS services and to scan pre-Java EE 5 web application modules and EJB modules for service clients during application installation. Because the default behavior for WAS v7.0 and later is to not scan pre-Java EE 5 modules for annotations during application installation or server startup, to preserve backward compatability with the feature pack from previous releases, configure either the UseWSFEP61ScanPolicy property in the META-INF/MANIFEST.MF of a web application archive (WAR) file or EJB module or define the JVM custom property, com.ibm.websphere.webservices.UseWSFEP61ScanPolicy, on servers to request scanning during application installation and server startup. To learn more about annotations scanning, see the JAX-WS annotations information.


Tasks

  1. Develop a dynamic web services client.

    The Dispatch client API, javax.xml.ws.Dispatch, is an XML messaging-oriented client intended for advanced XML developers who prefer using XML constructs. To write a Dispatch client, we must have expertise with the Dispatch client APIs, the supported object types, and knowledge of the message representations for the associated Web Services Description Language (WSDL) file. The Dispatch client API requires application clients to construct messages or payloads as XML and requires a detailed knowledge of the message or message payload. We do not need a WSDL file if we are developing a dynamic client.

  2. (Optional) Assemble a web services-enabled client JAR file into an enterprise archive (EAR) file. Complete this step if we are developing a JAX-WS web services client that runs in the Java EE client container.
  3. (Optional) Assemble a web services-enabled client web application archive (WAR) file into an EAR file. Complete this step if we are developing a JAX-WS web services client that runs in the Java EE web container.
  4. (Optional) Deploy the web services client application. Complete this step to deploy a JAX-WS web services client that runs in the Java EE client container.
  5. Test the web services-enabled client application. We can test an unmanaged client JAR file or a managed client application.

We have created and tested a web services client application.


What to do next

After you develop a web services application client, and the client is statically bound, the service endpoint used by the implementation is the one that is identified in the WSDL file that we used during the development process. During or after installation of the web services application, we might want to change the service endpoint. For managed clients, we can change the endpoint with the administrative console or the wsadmin scripting tool. For unmanaged JAX-WS web services clients, we can change the endpoint from within the client application.

We can additionally consider customizing the web services by implementing extensions to the web services client. Some examples of these extensions include sending and receiving values in SOAP headers or sending and receiving HTTP or JMS transport headers. To learn more about these extensions, read about implementing extensions to web services clients.


Related:

  • JAX-WS client programming model
  • Web services
  • JAX-WS
  • Implement static JAX-WS web services clients
  • Change SOAP message encoding to support WSI-Basic Profile
  • Testing web services-enabled clients
  • Configure web services client bindings
  • Set up a development environment for web services
  • Example: Installing a web services sample with the console
  • Implement web services applications with JAX-WS
  • Implement web services applications from existing WSDL files with JAX-WS
  • Task overview: Implementing web services applications
  • Web services client to web container optimized communication
  • JAX-WS annotations
  • Artifacts used to develop web services
  • Mapping between Java language, WSDL and XML for JAX-WS applications
  • Web services specifications and APIs
  • Set up UserName token Web Services Security
  • Digital signature Web Services Security
  • Lightweight Third-Party Authentication (LTPA) token Web Services Security