In a service requester pipeline, an application program creates
a request, which is passed through a pipeline to the service provider. The
response from the service provider is returned to the application program
through the same pipeline.
When CICS® is
in the role of service requester, it performs the following operations:
- Use data provided by the application program to construct a request.
- Send the request to the service provider.
- Receive a response from the service provider.
- Examine the response, and extract the contents that are relevant to the
original application program.
- Return control to the application program.
Figure 1 illustrates a pipeline
of three message handlers in a service requester setting:
Figure 1. A service requester pipeline
- An application program creates a request.
- Message handler 1 receives the request from the application program, performs
some processing, and passes the request to handler 2 (To be precise, it returns
control to CICS,
which manages the pipeline. CICS then passes control to the next message handler).
- Message handler 2 receives the request from handler 1, performs some processing,
and passes the request to handler 3.
- Message handler 3 receives the request from handler 2, performs some processing,
and passes the request to the service provider.
- Message handler 3 receives the response from the service provider, performs
some processing, and passes it to handler 2.
- Message handler 2 receives the response from handler 3, performs some
processing, and passes it to handler 1.
- Message handler 1 receives the response from handler 2, performs some
processing, and returns the response to the application program.