Async Invoke
Introduction
Deploying the Process
Running the Process

Asyncronous Invocation

Introduction

This sample shows the use of asynchronous one-way invokes and correlation data. The BPEL process receives a doc/literal message, calls an external echo Web service via a one-way invoke, and uses a receive to wait for a reply to come in via a separate callback message. The service sleeps for 15 seconds before sending its reply.

Invokes can be two-way or one-way. When two-way, the invoke waits for a reply from the Web service it has invoked. In that case, a WSDL fault may be returned as well. When an invoke is one-way, the invoke does not wait for a reply, nor will it ever receive a WSDL fault. An asynchronous invoke requires only an input variable. No output variable is specified.

The diagram below represents the BPEL process. First, the process receives a start message that contains an input string. The following assign activity copies that string into the input message for the first invoke. The first invoke is one-way; it sends the input message but does not wait for a reply. Next, the receive activity waits for an incoming message; in this case that is the callback message coming from the Web service we just invoked. Finally, the reply at the end of the process returns the response from the Web service.

The Web service used by the BPEL process uses java.util.logging.Logger to log messages about the echo-receiving thread. The log file is named async_service_debug.txt, and is created in the java.io.tmpdir directory. Since the Web service is run within an app server, the server's value of java.io.tmpdir is used. For example, under Tomcat running on Windows the value of java.io.tmpdir is %CATALINA_HOME%\temp.

Deploying the Process

You need to deploy the BPEL process and the Web service. To deploy the BPEL process, see Deploying the Samples.

To deploy the Web service, copy the file async_echo_web_services.wsr from the Resources/dist directory to the place appropriate for your app server. For example, on Tomcat that would be the $CATALINA_HOME/bpr directory.

Running the Process

See Running the Samples. The service name to use is AsyncEchoCallerService. The sample data file async_echo.xml can be used as input for this example. Remember that when you submit the sample data, the service will take 15 seconds to respond.