Mediation primitives and nodes

Tip: Wire the input and output terminals of a mediation primitive before you set its properties. This will make your input and output message types known to the editor, and will save you time when setting the properties.

These topics describe the properties of mediation primitives and nodes. These topics do not discuss marking properties for promotion. For information on promoted properties, see Changing the value of mediation flow properties at run time.

Table 1. Mediation primitives and nodes

Icon	Primitive or node	Description
	Input	Propagates the message to the primitive or node to which it is wired. The properties to be stored in the message context are specified in the details page of the input node's properties view. These properties can be accessed by mediation primitives later in the flow.
	Input Response	The input response node is an end point in the request and response flows. It returns the processed message as a response to the source operation. In a request flow, you can use the input response in certain conditional situations. For example if an input error detected, the message can return immediately to the source without invoking the callout.
	Callout	Receives the message and invokes the requested service and operation. There is a callout node for each connected target operation in the mediation flow.
	Callout response	A starting point for the response flow. It forwards the message received from the target operation into the response flow.
	Input Fault	The input response node is an end point in the request and response flows. It returns a fault message as a response to the source operation. In a request flow, you can use the fault response in certain conditional situations. For example if an input error is detected, a fault message can be returned immediately to the source without invoking the callout. A fault response node has an input terminal for each fault defined on the operation.
	Callout Fault	The callout fault node is an end point in the response flow. When a WSDL fault occurs in the invoked operation, the callout fault propagates the fault message to the primitive or node to which it is wired. The callout fault has an output terminal for each fault message type defined in the target operation.
Transformation
	Custom Mediation primitive	Allows you to implement your own mediation logic using Java™ code.
	Database Lookup mediation primitive Example: Database Lookup mediation primitive	Searches values from a database and stores them in the message.
	Message Element Setter mediation primitive	Sets, copies or deletes the value of message elements as the message passes through a mediation flow.
	Business Object Map mediation primitive	Allows you to map data between differently structured business objects. This allows services that use different business objects to communicate and exchange data.
	Set Message Type mediation primitive	Allows you to overlay weakly-typed message fields with more complex structures and manipulate them easier. It can also be used to overlay strong-typed fields with a derived type.
	MQ Header Setter mediation primitive	Creates, sets, copies or deletes MQ message headers.
	SOAP Header Setter mediation primitive	Creates, sets, copies or deletes SOAP message headers.
	HTTP Header Setter mediation primitive	Creates, sets, copies or deletes HTTP message headers.
	JMS Header Setter mediation primitive	Creates, sets, copies or deletes JMS message headers.
	Data Handler mediation primitive	Transforms a part of a message. It is used to convert an element of a message from a physical format to a logical structure or a logical structure to a physical format. For example, from a comma delimited string to a business object.
	Mapping mediation primitive	Transforms messages, or changes message content according to an XSL style sheet that maps between the source and target message types.
Routing
	Message Filter mediation primitive	Conditionally routes messages based on the results of pattern evaluation. A pattern is evaluated against the message, and if the result is true, the message is propagated to a terminal associated with the pattern.
	Endpoint Lookup mediation primitive	Queries the WebSphere® Service Registry Repository and retrieves service endpoints. The endpoints retrieved are based on user defined search criteria, and the retrieved endpoints are placed in the primitiveContext element in the message context. The retrieved endpoints can then be used to dynamically invoke a service, depending on the match policy specified.
	Fan Out mediation primitive	Performs broadcasting and to aggregate service responses in conjunction with the Fan In mediation primtiive
	Fan In mediation primitive	Combines multiple messages for aggregation. Fan In must be used in conjunction with the Fan Out mediation primitive.
	Service Invoke mediation primitive	Call an intermediary service inline within a mediation flow. It can retry a failed call, as well as route it to another service or different endpoints of the service.
	Type Filter mediation primitive	Allows you to direct messages down different paths of a mediation flow, based on the message type.
	Policy Resolution mediation primitive	Allows the runtime administrator to dynamically configure the mediation flow by modifying a policy .
Tracing
	Message Logger mediation primitive	Logs a copy of the message to a database for future retrieval or audit.
	Event Emitter mediation primitive	Emits custom base events at a significant point in the message flow.
Error Handling
	Fail mediation primitive	Throws an exception and stops the flow when there is a failure in a mediation primitive.
	Stop mediation primitive	Silently stops the flow; this is an expected termination and is not caused by an exception.
Mediation Subflow
	Mediation subflows	A mediation subflow is a preconfigured set of mediation primitives, run in the context of a parent flow, that are wired together to realize a common pattern or use case. Mediation subflows can be shared among mediation flows.