WebSphere

Overview of mediation policies

To use mediation policies effectively, you should understand the concepts behind them and plan your overall system. This topic explains the concepts, and also explains how the development and administration teams interact to produce mediation policies.

Introduction

When you use WebSphere® Integration Developer to create SCA modules that contain mediation flows, any module property that you choose to promote (make visible to the run time) is also a dynamic property, so long as the property exists at the top level. Dynamic properties can be overridden, at run time, using mediation policies in a registry. After you deploy an SCA module to your run time, you can see the dynamic module properties, and values, from the administrative console; using mediation policies you can override these values. Whether property values are overridden for a service interaction depends on the message being processed and the configuration of the mediation policy.

Details

When you export your SCA module, WebSphere Integration Developer generates a default mediation policy for each property group in your SCA module. For example, if your SCA module contains three property groups, WebSphere Integration Developer generates three default mediation policies each containing all the dynamic properties belonging to one group. The default mediation policies represent the values given to all dynamic properties, at development time. Although WebSphere Integration Developer generates default mediation policies, it does not attach them to the SCA module. You must decide how to use the default mediation policies.

Generally, you should use default mediation policies without any associated conditions, and create your own mediation policies if you want to have conditional mediation policies. Before you can create conditional mediation policies, in WebSphere Service Registry and Repository (WSRR), you must define the conditions in WebSphere Integration Developer. In WSRR, you create conditions on the mediation policy attachment that WSRR generates when you attach a mediation policy to an SCA module. At run time, the conditions (sometimes referred to as gate conditions) must be met before the mediation policy can be used.
Note: Mediation policies with gate conditions have a higher precedence than mediation policies without gate conditions. For more information, see the mediation policy processing model.

You can use WSRR classifications with your mediation policies. WSSR supports many classification systems, including life cycle classifications that you can use to govern your mediation policies.

Overview of development and administrative tasks

In order to use mediation policies, the developer, the runtime administrator, and the WSRR administrator must work together. They must create and integrate the SCA modules and mediation policies required.
  1. From WebSphere Integration Developer:
    1. Create an SCA module containing a Policy Resolution mediation primitive. Generally, any other mediation primitives in the SCA module should come after the Policy Resolution mediation primitive, and have at least one dynamic property.
    2. Promote the module properties you want to override, assigning each property an appropriate alias and group.
    3. Optional: Create conditions on the Policy Resolution mediation primitive.
    4. Optional: Create classifications on the Policy Resolution mediation primitive. The classifications must match the WSRR classification URIs.
    5. Export the SCA module.
      Note: If you have created a versioned SCA module, you must export your module as a command line deployment; otherwise, you can export your SCA module in an EAR file.
  2. From the run time:
    1. Ensure you have a suitable WSRR definition for your SCA module.
    2. Optional: If you have a versioned SCA module, you must run serviceDeploy on each of the exported modules to generate an EAR file.
    3. Optional: If you have a versioned SCA module that you want to deploy to clusters, you must run createVersionedSCAModule to create a new EAR file that contains a unique instance of a versioned SCA module. You must create one instance of the module for every cluster you want to deploy to.
      Note: You must load your versioned SCA modules into WSRR from the new EAR files.
    4. Deploy the SCA module.
  3. From WSRR:
    1. Load the SCA module.
    2. Optional: Create your own mediation policies.
    3. Attach the appropriate mediation policies to your SCA module.
    4. Optional: Create gate conditions.
    5. Optional: Make your policy document governed.
    6. Optional: Add non-life-cycle classifications to your policies.

Planning

Before you develop mediation policies you should plan your overall system:
  • Decide which WSRR instance you will use.
  • Decide what mediation primitive properties need to be overridden using mediation policies.
  • Decide on the property group name (or names). The group name helps to form the namespace of the mediation policy.
  • Decide on your mediation policy pattern.
  • Optional: Decide if you need to create your own mediation policies, rather than use only the default mediation policies. If you choose to create your own mediation policies, you should decide on their identifiers. The namespace and identifier, when taken together, must be unique across the instance of WSRR that contains the mediation policy.
  • Decide if you need any conditional mediation policies. At run time, gate conditions must be satisfied before a conditional mediation policy can be used. In WebSphere Integration Developer, every gate condition must be specified on the Policy Resolution mediation primitive as a Policy condition name. In WSRR, the gate conditions are specified on the mediation policy attachment.
  • Decide if you want to use WSRR classifications. You must specify the classifications you want to use, in both WebSphere Integration Developer and in WSRR.

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Timestamp icon Last updated: 20 June 2010 00:38:38 BST (DRAFT)


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