Writing a mediation handler

We can write a mediation handler, add mediation function to it, and prepare it for installation on an application server.

We should have access to a Java programming environment, and an assembly tool such as IBM Rational Application Developer.

A mediation handler can be deployed. Each mediation handler executes some specific message processing at run time, for example transforming a message format, or routing a message to a particular destination. A mediation handler is a Java program framework, to which we add the code that performs the mediation function.

We can define a mediation handler class either in a Java project or an EJB project (which is needed for the deployment artifact). Your programming and deployment artifacts can be separated in different projects. The following steps are for an EJB project, but the steps are very similar to create a Java project, because we define a target server for either a Java project or an EJB project and the server runtime plug-in sets the class path correctly.

Tasks

1. Create a new EJB project:
   1. Switch to the Java EE perspective to work with Java EE projects. Click Window > Open Perspective > Other > Java EE.

   2. From the File menu, select New > Project.

   3. Expand the Java EE folder, and select Enterprise Application Project. Click Next.

   4. Optional: If we have created a Java project instead of an EJB project, right-click on the Java project folder icon for the context menu and select Properties. When the Properties panel appears, select the Server properties and target the project to an appropriate server for our system, as in the next step.

   5. Enter a name for the project and target the project to an appropriate server for our system. (If this is the first time you target this server, click New....) Click Next to take you to the EAR Module Projects window.

   6. Click New Module....

   7. Create a new module project by selecting the check box against EJB project, and entering the name of our mediation handler.

   8. Click Finish. We are returned to the EAR Module Projects window.

   9. Click Finish to create the new project.

2. Create a mediation handler class by implementing the com.ibm.websphere.sib.mediation.handler.MediationHandler interface.

   1. From the File menu, select New > Java Class.

   2. Specify the source folder for our mediation EAR project.

   3. Specify a name for our mediation handler.

   4. Select Superclass java.lang.Object.

   5. Select Interface com.ibm.websphere.sib.mediation.handler.MediationHandler.

   6. Select the Inherited abstract methods check box.

   7. Click Finish to create the new mediation handler class.

3. Add functional code that transforms or routes messages to your mediation handler using the IBM Rational Application Developer. See Add mediation function to handler code. Beware that the default return value for the handle method created by the toolkit is false, which causes the message to be discarded. We must change the return value to true to preserve the message.
4. Generate an EAR file from your mediation handler class. Follow the instructions in the IBM Rational Application Developer documentation.

What to do next

Next, we are ready to install the EAR file containing your mediation handler into the application server.

Related:

Mediation programming

Mediation handlers and mediation handler lists

IBM Rational Application Developer documentation