Using mediation policies you can dynamically
control service interactions, using contextual information. Learn
how modules, target services, and mediation policies interrelate.
Mediation policies
Using mediation policies
you can dynamically configure service interactions, by overriding
the values of module properties. The module properties that you can
override are defined in a mediation flow. You define the override
values in a mediation policy.
Mediation policies are stored
in WebSphere® Service Registry
and Repository (WSRR), but you can create them using the Mediation
Policy Administration widget.
Creating modules that can use mediation policies
You
use IBM Integration Designer to create modules with a mediation flow.
The mediation flow must include a Policy Resolution mediation primitive,
which can access mediation policies in WSRR. You define whether the
Policy Resolution mediation primitive retrieves mediation policies
associated with the module, a target service, or both.
When
you create the mediation flow you must include other mediation primitives,
that have properties you want to override.
- Use IBM Integration Designer to create a module containing a Policy
Resolution mediation primitive. The Policy Resolution primitive must
be placed before any primitives that have properties you want to
modify.
- Configure the Policy Resolution primitive.
- Specify the WSRR definition to use, or take the default definition.
- Define whether to retrieve mediation policies associated with
the module, a target service, or both.
- If you want to use a gate condition, create
a Policy condition name that matches the gate
condition on the policy. Specify where the condition value is found
in the message, by providing an XPath expression. For example, you
could create a Policy condition name of Age and
an XPath expression of /body/priceChecker/request/Age.
When service requests are processed, the value of condition Age is
set from /body/priceChecker/request/Age.
- If you want to associate mediation policies
with a target service rather than a module, add an Endpoint Lookup
mediation primitive before the Policy Resolution mediation primitive.
- Add other mediation primitives.
- Promote any properties that you want to override dynamically.
Only promoted properties can be overridden by mediation policies.
Configuring WebSphere ESB or IBM Business Process
Manager
The application server must contain your module
and be aware of the correct WSRR.
- Deploy your module to WebSphere ESB or IBM Business Process Manager.
- Ensure that WebSphere ESB or IBM Business Process Manager have
a suitable WSRR definition for your module.
Configuring WSRR
When the Policy Resolution
mediation primitive processes service requests, it queries WSRR. Therefore,
WSRR must contain the relevant information about your modules and
services.
- Load the EAR file, containing your SCA module, into WSRR.
- If necessary, load the WSDL for the target
services that you want to use.
Using the Mediation Policy Administration widget
You
can use the Mediation Policy Administration widget
to create mediation policies and associate them with either modules
or target services. In addition, the widget creates policy attachments
that associate mediation policies with modules or target services.
The mediation policies and policy attachments are created in WSRR.
For
every property that you want to override, you add an assertion. The
widget refers to the properties that you want to override as assertions.
In WSRR, the property overrides are assertions on the policy. If you
want to create a conditional mediation policy, add a gate condition.
In WSRR, the gate conditions are user properties on the policy attachment.
- When you create a policy attachment using the Mediation
Policy Administration widget, the widget creates a single
policy attachment and one mediation policy for each group that has
an assertion.
- When you delete a policy attachment using the Mediation
Policy Administration widget, the widget deletes the policy
attachment and any of the mediation policies it attached, unless the
policies are being used by a different attachment.
When you use the Mediation Policy Administration
widget to attach mediation policies to target services, you can attach
the policies at the following levels:
- Service
- Endpoint
- Operation