Mediation modules

Mediation modules are Service Component Architecture (SCA) modules that can change the format, content or target of service requests.

Mediation modules operate on messages that are in flight between service requesters and service providers. They allow you to route messages to different service providers. They also let you transform messages: you can amend message content or form. In addition, mediation modules can provide functions such as message logging, and error processing that is tailored to your requirements.

You can change certain aspects of mediation modules dynamically, from the WebSphere Process Server administrative console, without having to redeploy the module.

Components of mediation modules

Among the items that mediation modules contain are the following:
  • Imports
    • Imports define interactions between SCA modules and service providers.
    • Imports allow SCA modules to call external services as if they were local.
    • Mediation module imports can be viewed from WebSphere Process Server, and if the import binding is a Web service or SCA binding then it can be modified.
  • Exports
    • Exports define interactions between SCA modules and service requesters.
    • Exports allow an SCA module to offer a service. Exports define the external interfaces (access points) of an SCA module.
    • Mediation module exports can be viewed from WebSphere Process Server.
  • SCA components
    • SCA components, or service components, are SCA building blocks. You build SCA modules such as mediation modules, using SCA components. You can create and customize SCA modules and components graphically, using WebSphere Integration Developer. In addition, you can customize some of the properties of SCA modules dynamically, from WebSphere Process Server administrative console, without having to redeploy the module.
    • Typically, mediation modules contain a specific type of SCA component called a mediation flow component. Mediation flow components define mediation flows. A mediation module can contain, at most, one mediation flow component.
    • A mediation flow component can contain one mediation primitive, a number of mediation primitives or no mediation primitives. WebSphere Process Server supports a supplied set of mediation primitives that provide functionality for message routing and transformation. One of the mediation primitives that WebSphere Process Server supports allows you to invoke custom logic.
    • A mediation module does not have to contain a mediation flow component. The purpose of a mediation module that does not contain a mediation flow component is to transform service requests from one protocol to another. For example, a service request might be made using SOAP/JMS but need transforming to SOAP/HTTP before sending on.
    Note: You can view mediation modules from WebSphere Process Server. You can also make certain changes to mediation modules from WebSphere Process Server. However, you cannot view or change the SCA components from inside a WebSphere Process Server module. Use WebSphere Integration Developer to customize SCA components.
    Figure 1. Simplified example of a mediation module. The mediation module contains one mediation flow component. The mediation flow component contains mediation primitives.
    The mediation module contains one mediation flow component. The mediation flow component contains mediation primitives.
  • Properties
    • Mediation primitives have properties, some of which can be displayed in the administrative console as additional properties of an SCA module.
    • In order for mediation primitive properties to be visible from the WebSphere Process Server administrative console the integration developer must flag the properties as promoted. Certain properties lend themselves to being administratively configured and WebSphere Integration Developer describes these as promotable properties, because they can be promoted from the integration cycle to the administrative cycle. Other properties are not suitable for administrative configuration, typically because modifying them affects the mediation flow in such a way that you need to redeploy the mediation module. WebSphere Integration Developer lists the properties that you can choose to promote under the Promoted Properties of a mediation primitive.
    • You can use the WebSphere Process Server administrative console to change the value of promoted properties without having to redeploy a mediation module, or restart the server or module. New invocations of mediation flows use property changes immediately, unless the changes occur in a deployment manager cell. If changes occur in a deployment manager cell then they take effect after all nodes in the cell have been synchronized. Inflight invocations of mediation flows continue to use previous values.
      Note: If you want to change the property names and types of mediation primitives, and not the property values, you should use WebSphere Integration Developer.

Deploying mediation modules

Mediation modules are created using WebSphere Integration Developer, and are generally deployed to WebSphere Process Server inside an EAR (enterprise archive) file.

You can change the value of promoted properties at deployment time.

You can export a mediation module from WebSphere Integration Developer, and cause WebSphere Integration Developer to package the mediation module inside a JAR (Java archive) file, and the JAR file inside an EAR file. You can then deploy the EAR file, by installing a new application from the administrative console.

Mediation modules can be thought of as one entity. However, SCA modules are defined by a number of XML files stored in a JAR file.

Figure 2. Simplified example of an EAR file containing a mediation module. The EAR file contains JARs. The utility JAR file contains a mediation module.
The EAR file contains JARs. The utility JAR file contains a mediation module.

Last updated: Wed 06 Dec 2006 07:08:08

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