Learn about a typical end-to-end scenario
where the broker implements a Web service.
An existing C or COBOL based system offers
some business logic which can usefully be exposed as a Web service.
The
broker can start the operation on the existing system, that is, the system
exposes an interface to the broker. Typically the existing system is enabled
for WebSphere® MQ; it receives WebSphere MQ messages
containing application data, dispatches these to the underlying implementation,
and then packages the return values as an WebSphere MQ response.
The data structures supplied to, and returned by, these existing operations
are defined in a C header file or COBOL copybook.
The Web service offers
an interface based on the operations already exposed by the existing system.
This interface might comprise all of the existing operations, or a subset
of the existing operations or composite operations, or both.
To define
your interface:
- Look at the business function offered by the existing system.
- Select the subset of this business function to be exposed.
- Decide how to represent the subset in the interface, that is, as many
discrete operations, or as fewer multipurpose operations.
You must decide whether you want the Web service interface to
be RPC-style or document-style. For more information about Web services, WSDL
and message flows, see
Relationship of WSDL to Message Model.
- An RPC-style interface is typically designed to map to an underlying set
of operations that is provided by an API, and the individual operations (method
calls) have relatively small payloads.
- A document-style interface might have fewer operations each with a larger
payload; for example, a document might represent a loan request.
The
Web Services
Interoperability Organization (WS-I) recommends
the use only of document-style WSDL, but many older Web services use RPC-style.
To
implement the scenario: