5 Creating Buffered Web Services

Overview of Buffered Web Services

When a buffered operation is invoked by a client, the method operation goes on a JMS queue and WebLogic Server deals with it asynchronously. As with Web service reliable messaging, if WebLogic Server goes down while the method invocation is still in the queue, it will be dealt with as soon as WebLogic Server is restarted. When a client invokes the buffered Web service, the client does not wait for a response from the invoke, and the execution of the client can continue.

Creating a Buffered Web Service: Main Steps

The following procedure describes how to create a buffered Web service and a client Web service that invokes an operation of the buffered Web service. The procedure shows how to create the JWS files that implement the two Web services from scratch. If you want to update existing JWS files, use this procedure as a guide. The procedure also shows how to configure the WebLogic Server instance that hosts the buffered Web service.

It is assumed that you have set up an Ant-based development environment and that you have a working build.xml file to which you can add targets for running the jwsc Ant task and deploying the generated buffered Web service. It is further assumed that you have a similar setup for the WebLogic Server instance that hosts the client Web service that invokes the buffered Web service. For more information, see in Getting Started With JAX-RPC Web Services for Oracle WebLogic Server:

• "Use Cases and Examples"

• "Developing WebLogic Web Services"

• "Programming the JWS File"

• "Invoking Web Services"

<jwsc
    srcdir="src"
    destdir="${service-ear-dir}" >
    <jws
      file="examples/webservices/async_buffered/AsyncBufferedImpl.java" 
    />
</jwsc>

prompt> ant build-clientService deploy-clientService

prompt> ant build-clientService deploy-clientService

Configuring the Host WebLogic Server Instance for the Buffered Web Service

Configuring the WebLogic Server instance on which the buffered Web service is deployed involves configuring JMS resources, such as JMS servers and modules, that are used internally by the Web services runtime.

You can configure these resources manually or you can use the Configuration Wizard to extend the WebLogic Server domain using a Web services-specific extension template. Using the Configuration Wizard greatly simplifies the required configuration steps; for details, see "Configuring Your Domain For Web Services Features" in Getting Started With JAX-RPC Web Services for Oracle WebLogic Server.

If you prefer to configure the resources manually, perform the following steps.

http://host:port/console

Programming Guidelines for the Buffered JWS File

The following example shows a simple JWS file that implements a buffered Web service; see the explanation after the example for coding guidelines that correspond to the Java code in bold.

package examples.webservices.buffered;

import javax.jws.WebMethod;
import javax.jws.WebService;
import javax.jws.Oneway; 

import weblogic.jws.WLHttpTransport;
import weblogic.jws.MessageBuffer; 
import weblogic.jws.BufferQueue; 

@WebService(name="BufferedPortType",
            serviceName="BufferedService",
            targetNamespace="http://example.org")

@WLHttpTransport(contextPath="buffered",
                 serviceUri="BufferedService",
                 portName="BufferedPort")

// Annotation to specify a specific JMS queue rather than the default
@BufferQueue(name="my.jms.queue") 

/**
 * Simple buffered Web Service.
 */

public class BufferedImpl {

  @WebMethod()
  @MessageBuffer(retryCount=10, retryDelay="10 seconds") 
  @Oneway() 
  public void sayHelloNoReturn(String message) { 
    System.out.println("sayHelloNoReturn: " + message);

  }
}

Follow these guidelines when programming the JWS file that implements a buffered Web service. Code snippets of the guidelines are shown in bold in the preceding example.

• Import the JWS annotations used for buffered Web services:

  import javax.jws.Oneway;
  import weblogic.jws.MessageBuffer;
  import weblogic.jws.BufferQueue;
  

  See the following bullets for guidelines on which JWS annotations are required.

• Optionally use the class-level @BufferQueue JWS annotation to specify the JNDI name of the JMS queue used internally by WebLogic Server when it processes a buffered invoke; for example:

  @BufferQueue(name="my.jms.queue")
  

  If you do not specify this JWS annotation, then WebLogic Server uses the default Web services JMS queue (weblogic.wsee.DefaultQueue).

  You must create both the default JMS queue and any queues specified with this annotation before you can successfully invoke a buffered operation. See Configuring the Host WebLogic Server Instance for the Buffered Web Service for details.

• Use the @MessageBuffer JWS annotation to specify the operations of the Web service that are buffered. The annotation has two optional attributes:

  • retryCount: The number of times WebLogic Server should attempt to deliver the message from the JMS queue to the Web service implementation (default 3).

  • retryDelay: The amount of time that the server should wait in between retries (default 5 minutes).

  For example:

  @MessageBuffer(retryCount=10, retryDelay="10 seconds")
  

  You can use this annotation at the class-level to specify that all operations are buffered, or at the method-level to choose which operations are buffered.

• If you plan on invoking the buffered Web service operation synchronously (or in other words, not using the asynchronous request-response feature), then the implementing method is required to be annotated with the @Oneway annotation to specify that the method is one-way. This means that the method cannot return a value, but rather, must explicitly return void. For example:

  @Oneway()
  public void sayHelloNoReturn(String message) {
  

  Conversely, if the method is not annotated with the @Oneway annotation, then you must invoke it using the asynchronous request-response feature. If you are unsure how the operation is going to be invoked, consider creating two flavors of the operation: synchronous and asynchronous.

  See Chapter 2, "Invoking a Web Service Using Asynchronous Request-Response," and Chapter 6, "Using the Asynchronous Features Together."

Programming the JWS File That Invokes the Buffered Web Service

You can invoke a buffered Web service from both a stand-alone Java application (if not using asynchronous request-response) and from another Web service. Unlike other WebLogic Web services asynchronous features, however, you do not use the @ServiceClient JWS annotation in the client Web service, but rather, you invoke the service as you would any other. For details, see "Invoking a Web Service from Another Web Service" in Getting Started With JAX-RPC Web Services for Oracle WebLogic Server.

The following sample JWS file shows how to invoke the sayHelloNoReturn operation of the BufferedService Web service:

package examples.webservices.buffered;

import java.rmi.RemoteException;
import javax.xml.rpc.ServiceException;

import javax.jws.WebService;
import javax.jws.WebMethod;

import weblogic.jws.WLHttpTransport;

import examples.webservices.buffered.BufferedPortType;
import examples.webservices.buffered.BufferedService_Impl;
import examples.webservices.buffered.BufferedService;

@WebService(name="BufferedClientPortType",
            serviceName="BufferedClientService",
            targetNamespace="http://examples.org")

@WLHttpTransport(contextPath="bufferedClient",
                 serviceUri="BufferedClientService",
                 portName="BufferedClientPort")

public class BufferedClientImpl {

  @WebMethod()
  public String callBufferedService(String input, String serviceUrl)
        throws RemoteException {

    try {

    BufferedService service = new BufferedService_Impl(serviceUrl + "?WSDL");
    BufferedPortType port = service.getBufferedPort();

    // Invoke the sayHelloNoReturn() operation of BufferedService

    port.sayHelloNoReturn(input);

    return "Invoke went okay!";

    } catch (ServiceException se) {

         System.out.println("ServiceExcpetion thrown");
         throw new RuntimeException(se);

      }
  }
}

Updating the build.xml File for a Client of the Buffered Web Service

To update a build.xml file to generate the JWS file that invokes a buffered Web service operation, add taskdefs and a build-clientService targets that look something like the following example. See the description after the example for details.

<taskdef name="jwsc"
    classname="weblogic.wsee.tools.anttasks.JwscTask" />

<target name="build-clientService">

    <jwsc
        enableAsyncService="true"
        srcdir="src"
        destdir="${clientService-ear-dir}" >

        <jws file="examples/webservices/buffered/BufferedClientImpl.java">
           <clientgen 
             wsdl="http://${wls.hostname}:${wls.port}/buffered/BufferedService?WSDL" 
             packageName="examples.webservices.buffered"/> 

        </jws>

    </jwsc>

  </target>

Use the taskdef Ant task to define the full classname of the jwsc Ant tasks.

Update the jwsc Ant task that compiles the client Web service to include a <clientgen> child element of the <jws> element so as to generate and compile the JAX-RPC stubs for the deployed BufferedService Web service. The jwsc Ant task automatically packages them in the generated WAR file so that the client Web service can immediately access the stubs. You do this because the BufferedClientImpl JWS file imports and uses one of the generated classes.