Mediation components operate on message flows between service components.
The capabilities of a mediation component are implemented by mediation
primitives, which implement standard service implementation types.
A mediation component has one or more flows. For example, one for request
and one for reply.
WebSphere Process Server supports
a supplied set of mediation primitives,
which implement standard mediation capabilities for mediation modules deployed
into WebSphere Process Server.
If you need special mediation capabilities, you can develop your own custom mediation primitives.
A mediation primitive defines one "in" operation that processes or
handles messages that are represented by service message objects (SMO). A mediation primitives can also
define "out" operations that send messages to another component or module.
Figure 1. Mediation module containing three mediation primitives
Mediation primitives typically
function at the level of a single operation, with possible mediation of the
request and response. In some cases, you can specify mediation primitives down
to the level of a single parameter on an operation. For example, selectors
can operate at the operation level or parameter level.
You can use WebSphere Integration Developer to
graphically model and assemble mediation components from mediation primitives,
and assemble mediation modules from mediation components.
Supported mediation primitives
The following set
of
mediation primitives are
supported by
WebSphere Process Server:
- Custom Mediation
- Runs custom logic. The Custom Mediation primitive can call an external Service Component Architecture (SCA) component that you
provide.
- The operation that is called must be a two-way operation.
- The target SCA component must
exist in the same mediation module as
the Custom Mediation primitive.
- Database Lookup
- Modifies messages, using information from a user-supplied database.
- You must set up a database, datasource and any server authentication settings
for the Database Lookup mediation primitive to
use.
- The Database Lookup mediation primitive can
read from only one table.
- The specified key column must contain a unique value.
- The data in the value columns must be either a Java primitive or a Java
String (or be able to be cast to a Java primitive or a Java String).
- Endpoint Lookup
- Allows for dynamic routing of requests, by searching for service endpoints
in a repository.
- Service endpoint information is retrieved from a WebSphere Service Registry
and Repository (WSRR), which can be local or remote.
- You can make registry changes from the administrative console.
- Event Emitter
- Enhances monitoring, by emitting events from within a mediation flow.
- The events are sent in the form of Common Base Events (CBE) and are sent
to a Common Event Infrastructure (CEI) server.
- To fully utilize Event Emitter information, event consumers need to understand
the structure of the CBE. The CBE has an overall schema but this does not
model the application specific data, contained in the extended data elements.
To model the extended data elements, the WebSphere Integration Developer tools
generate a CEI event catalog definition file for each of the configured Event
Emitter mediation primitives.
Event catalog definition files are export artifacts that are provided to help
you, they are not used by WebSphere Integration Developer or
by the WebSphere Process Server runtime.
You should refer to the event catalog definition files when you create applications
to consume Event Emitter events.
- You can specify other monitoring from WebSphere Process Server.
For example, you can monitor events to be emitted from imports and exports.
What the Event Emitter mediation primitive does
is let you send events from inside a mediation flow component. You can then
view Event Emitter events using the CBE browser on WebSphere Process Server.
- Fail
- Generates a failure in the flow.
- Message Element Setter
- Provides a simple mechanism for setting the content of message headers
or bodies, it does not change the type of the message.
- Message Filter
- Routes messages down different paths, based on the message content.
- Message Logger
- Logs messages in a database. The messages are stored as XML, therefore
data can be post-processed by XML-aware applications.
- The database schema is defined by IBM.
- On distributed platforms, the default installation of WebSphere Process Server creates a
stand-alone application server, and a Cloudscape database and datasource.
By default, WebSphere Integration Developer configures
Message Logger mediation primitives to use this Cloudscape database. WebSphere Process Server also provides
a script, called createMessageLoggerResource.jacl, that creates a Cloudscape
database.
- You can use the coreDBUtilty command
to create a DB2 message logging database on a remote z/OS system.
- If you want to create your own database and datasource, using the administrative
console, then WebSphere Process Server provides
data definition language (ddl) files that describe the table schema. The Table.ddl
files are stored in: install_root/util/EsbLoggerMediation/database_
type/Table.ddl. Where database_ type refers to
the type of database, for example, CLOUDSCAPE_V50. If you create your own
database and want to use the default JNDI name for your datasource, then you
must remove the default datasource.
- Stop
- Stops a particular path in the flow, without generating an exception.
- XSLT
- Transforms messages.
- The XSLT mediation primitive can change the headers or the body of your
messages.
- You transform messages using an XSLT (Extensible Stylesheet Transformations)
1.0 transformation. The transformation operates on an XML serialization of
the message.
- SplitPath
- Select the target service (or another mediation), route to a specific
target, modify the routing path ...
- BOMapper
- Select the target service (or another mediation), route to a specific
target, modify the routing path ...
Last updated: Thu 26 Oct 2006 10:30:05
(c) Copyright IBM Corporation 2005, 2006.
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