WAS v8.5 > WebSphere applications > Service integration > Mediations

Mediation programming

Using the capabilities of the mediation infrastructure, we can program mediations to customize the way that a service integration bus handles messages. You develop the mediation code within a component called a mediation handler, and add the mediation handler to a handler list, which is an application that is ready to deploy and install. We can connect a number of mediation handlers together in a mediation handler list to create a set of operations to run on a message.

A mediation handler is a Java program framework to which you add the code that operates on a message to perform the mediation function. For example, we can program mediations to process messages in any of the following ways:

• Reformat messages from the format produced by one application to the format required by another
• Route messages based on message content
• Distribute messages to more than one destination
• Augment messages by adding information to a message from another data source
• Transcode messages from one concrete representation to another

The following programming APIs are available for working with messages when we program a mediation:

MediationHandler API

A mediation handler must implement the MediationHandler interface. This interface defines the method that is invoked by the mediation runtime environment.

SIMessage and SIMessageContext APIs

These APIs allow your mediation to operate on the contents of the message.

SIMediationSession API

This API gives your mediation access to a service integration bus so the mediation can send and receive messages.

We create a handler list using an assembly tool, for example IBM Rational Application Developer, before deploying the mediation handler application as an Enterprise Archive (EAR file).

A handler list can contain one or many mediation handlers. At run time, each mediation handler in the list is invoked in sequence. Each time a handler returns a value of True, the same message context is passed to the next handler. If a handler returns the value False, then the context is not passed to the next handler. The message is discarded, and is not delivered to its target destination.

Subtopics

• SDO data graphs
  Service Data Objects (SDO) is an open standard for enabling applications to handle data from different data sources in a uniform way, as data graphs. SDO data graphs are an important concept for mediation programmers because we can use them to represent different types of message information in a standard way, giving a simple and powerful model for programming mediations.
• Coding tips for mediations programming
  Programming hints to help when we are writing mediation code.

Related

Writing a mediation handler

Reference:

MediationHandler
SIMessageContext
SIMessage
SIMediationSession

Related information:

IBM Rational Application Developer documentation

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