Programming Advanced Features of WebLogic Web Services Using JAX-RPC

Invoking a Web Service Using Asynchronous Request-Response

The following sections describe how to invoke a Web Service using asynchronous request-response:

Overview of the Asynchronous Request-Response Feature

When you invoke a Web Service synchronously, the invoking client application waits for the response to return before it can continue with its work. In cases where the response returns immediately, this method of invoking the Web Service might be adequate. However, because request processing can be delayed, it is often useful for the client application to continue its work and handle the response later on, or in other words, use the asynchronous request-response feature of WebLogic Web Services.

You invoke a Web Service asynchronously only from a client running in a WebLogic Web Service, never from a stand-alone client application. The invoked Web Service does not change in any way, thus you can invoke any deployed Web Service (both WebLogic and non-WebLogic) asynchronously as long as the application server that hosts the Web Service supports the WS-Addressing specification.

When implementing asynchronous request-response in your client, rather than invoking the operation directly, you invoke an asynchronous flavor of the same operation. (This asynchronous flavor of the operation is automatically generated by the jwsc Ant task.) For example, rather than invoking an operation called getQuote directly, you would invoke getQuoteAsync instead. The asynchronous flavor of the operation always returns void, even if the original operation returns a value. You then include methods in your client that handle the asynchronous response or failures when it returns later on. You put any business logic that processes the return value of the Web Service operation invoke or a potential failure in these methods. You use both naming conventions and JWS annotations to specify these methods to the JWS compiler. For example, if the asynchronous operation is called getQuoteAsync, then these methods might be called onGetQuoteAsyncResponse and onGetQuoteAsyncFailure.

Using Asynchronous Request-Response: Main Steps

The following procedure describes how to create a client Web Service that asynchronously invokes an operation in a different Web Service. The procedure shows how to create the JWS file that implements the client Web Service from scratch; if you want to update an existing JWS file, use this procedure as a guide.

For clarity, it is assumed in the procedure that:

It is further 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 service. For more information, see the following sections in Getting Started With WebLogic Web Services Using JAX-RPC:

When you invoke the StockQuoteClientService Web Service, which in turn invokes the StockQuoteService Web Service, the second invoke will be asynchronous rather than synchronous.

Configuring the Host WebLogic Server Instance for the Asynchronous Web Service

Configuring the WebLogic Server instance on which the asynchronous 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 WebLogic Web Services Using JAX-RPC.

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

Writing the Asynchronous JWS File

The following example shows a simple JWS file that implements a Web Service called StockQuoteClient that has a single method, asyncOperation, that in turn asynchronously invokes the getQuote method of the StockQuote service. The Java code in bold is described Coding Guidelines for Invoking a Web Service Asynchronously. See Example of a Synchronous Invoke to see how the asynchronous invoke differs from a synchronous invoke of the same operation.

package examples.webservices.async_req_res;

import weblogic.jws.WLHttpTransport;
import weblogic.jws.ServiceClient;
import weblogic.jws.AsyncResponse;
import weblogic.jws.AsyncFailure;

import weblogic.wsee.async.AsyncPreCallContext;
import weblogic.wsee.async.AsyncCallContextFactory;
import weblogic.wsee.async.AsyncPostCallContext;

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

import examples.webservices.async_req_res.StockQuotePortType;

import java.rmi.RemoteException;

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

@WLHttpTransport(contextPath="asyncClient",
                 serviceUri="StockQuoteClient",
                 portName="StockQuoteClientServicePort")

/**
 *  Client Web Service that invokes the StockQuote Service asynchronously.
 */

public class StockQuoteClientImpl {

  @ServiceClient(wsdlLocation="http://localhost:7001/async/StockQuote?WSDL",
                 serviceName="StockQuoteService", portName="StockQuote")

  private StockQuotePortType port;

  @WebMethod
  public void asyncOperation (String symbol, String userName) 
    throws RemoteException {

    AsyncPreCallContext apc = AsyncCallContextFactory.getAsyncPreCallContext();
    apc.setProperty("userName", userName);

    try {
      port.getQuoteAsync(apc, symbol );
      System.out.println("in getQuote method of StockQuoteClient WS");

     } catch (RemoteException re) {

        System.out.println("RemoteException thrown");
        throw new RuntimeException(re);
    }

  }

  @AsyncResponse(target="port", operation="getQuote")
  public void onGetQuoteAsyncResponse(AsyncPostCallContext apc, int quote) {
    // Get the userName property we set on AsyncPreCallContext
    String userName = (String)apc.getProperty("userName");
    System.out.println("-------------------");
    System.out.println(username + " Got quote " + quote );
    System.out.println("-------------------");
  }

  @AsyncFailure(target="port", operation="getQuote")
  public void onGetQuoteAsyncFailure(AsyncPostCallContext apc, Throwable e) {
    System.out.println("-------------------");
    e.printStackTrace();
    System.out.println("-------------------");
  }

}

Coding Guidelines for Invoking a Web Service Asynchronously

The following guidelines for invoking an operation asynchronously correspond to the Java code shown in bold in the example described in Writing the Asynchronous JWS File. These guidelines are in addition to the standard ones for creating JWS files. See Example of a Synchronous Invoke to see how the asynchronous invoke differs from a synchronous invoke of the same operation.

To invoke an operation asynchronously in your JWS file:

Using Asynchronous Pre- and Post-call Contexts

The AsyncPreCallContext and AsyncPostCallContext APIs describe asynchronous contexts that you can use in your Web Service for a variety of reasons. For example:

To use asynchronous pre- and post-call contexts:

Example of a Synchronous Invoke

The following example shows a JWS file that invokes the getQuote operation of the StockQuote Web Service synchronously. The example is shown only so you can compare it with the corresponding asynchronous invoke shown in Writing the Asynchronous JWS File.

package examples.webservices.async_req_res;

import weblogic.jws.WLHttpTransport;
import weblogic.jws.ServiceClient;

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

import java.rmi.RemoteException;

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

@WLHttpTransport(contextPath="syncClient",
                 serviceUri="SyncClient",
                 portName="SyncClientPort")

/**
 *  Normal service-to-service client that invokes StockQuote service
 *  synchronously.
 */

public class SyncClientImpl {

  @ServiceClient(wsdlLocation="http://localhost:7001/async/StockQuote?WSDL",
                 serviceName="StockQuoteService", portName="StockQuote")
  private StockQuotePortType port;

  @WebMethod
  public void nonAsyncOperation(String symbol) throws RemoteException {

    int quote = port.getQuote(symbol);

    System.out.println("-------------------");
    System.out.println("Got quote " + quote );
    System.out.println("-------------------");

  }

}

Updating the build.xml File When Using Asynchronous Request-Response

To update a build.xml file to generate the JWS file that invokes a Web Service operation asynchronously, add taskdefs and a build-clientService target that looks something like the following; 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/async_req_res/StockQuoteClientImpl.java" >

          <clientgen
            wsdl="http://${wls.hostname}:${wls.port}/async/StockQuote?WSDL"
            packageName="examples.webservices.async_req_res"/>

        </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 StockQuote 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. By default, the jwsc Ant task in this case generates both synchronous and asynchronous flavors of the Web Service operations in the JAX-RPC stubs. You do this because the StockQuoteClientImpl JWS file imports and uses one of the generated classes.

Disabling The Internal Asynchronous Service

By default, every WebLogic Server instance deploys an internal asynchronous Web Service that handles the asynchronous request-response feature. To specify that you do not want to deploy this internal service, start the WebLogic Server instance using the -Dweblogic.wsee.skip.async.response=true Java system property.

One reason for disabling the asynchronous service is if you use a WebLogic Server instance as a Web proxy to a WebLogic cluster. In this case, asynchronous messages will never get to the cluster, as required, because the asynchronous service on the proxy server consumes them instead. For this reason, you must disable the asynchronous service on the proxy server using the system property.

For details on specifying Java system properties to configure WebLogic Server, see “Specifying Java Options for a WebLogic Server Instance” in Managing Server Startup and Shutdown.

Using Asynchronous Request Response With a Proxy Server

Client applications that use the asynchronous request-response feature might not invoke the operation directly, but rather, use a proxy server. Reasons for using a proxy include the presence of a firewall or the deployment of the invoked Web Service to a cluster.

In this case, the WebLogic Server instance that hosts the invoked Web Service must be configured with the address and port of the proxy server. If your Web Service is deployed to a cluster, you must configure every server in the cluster.

This procedure describes how to create a network channel, the primary configurable WebLogic Server resource for managing network connection. Network channels enable you to provide a consistent way to access the front-end address of a cluster. For more information about network channels, see “Understanding Network Channels” in Configuring Server Environments.

For each server instance: