Mediation primitives plug in to the WebSphere® Integration Developer (WID tooling palette. They can be used as primitive operations when you are creating Access Gateway mediation flows.
A set of default flows is provided when you install the Access Gateway. To create a customized logic, you can utilize the WID tooling to assemble flows among the different components.
Each mediation primitives consists of Java™ code that implements a component interface for the Access Gateway. A mediation primitive is a logical unit that has a failure terminal and a number of input and output terminals.
Data objects are passed during execution of an Access Gateway flow between I/O terminals. The data objects use a representation called Service Message Object (SMO), for the SOAP (Simple Object Access Protocol) message that is being processed for a Web service invocation. The SMO object arrives at a mediation primitive's input terminal during execution flow, which allows control to be passed on to the primitive's mediate method.
The mediation primitive can then process the message and determine where to place the response on its defined output terminal, according to the semantics of that terminal. Mediation flows are created by wiring or connecting the input and output terminals.
Mediation primitives are the primary programming model for the Access Gateway subcomponents.
Mediation primitives use a pipeline architecture. You can insert additional mediation primitives anywhere in the flow, change the order of execution (subject to some constraints), and so on. The pipeline architecture is based on the SOAP processing model, where additional SOAP headers may be added, modified, or removed prior to passing execution to the next downstream element.
Each mediation primitive has unique semantics or expectations to define the input at its terminal and to specify the data that must be present in order to execute its logic. For example, a mediation primitive might insert additional headers to a SOAP message for processing by downstream elements, or it might require upstream primitives to insert headers. These semantics or expectations can result in constraints on how a particular component is used within a mediation flow.
The following components are considered mandatory for a base Access Gateway configuration and flow:
The mandatory components provide base services that support mediation primitives. The Transaction Identifier mediation primitive records information about the transaction within a table that is typically referenced by the Network Statistics mediation primitive. The Policy Retrieval mediation primitive retrieves policy data based on the requester, service, and operation being called. This data is used as decision parameters within the mediation primitive's execution flow.
The following components are optional plug-ins and are used by the default Access Gateway flow: