Request/Response processing

One common business integration scenario is an EIS initiated synchronous request. In this case, the EIS issues a request to retrieve or update data outside the bounds of the EIS, and expects a synchronous response.

Examples would be a web application that must check product availability before placing an order, or a call center service application that must access scheduling information before booking a service appointment. In both cases, the EIS user makes an inquiry, which requires real-time access to backend business data or processes, so that the user can make use of the result before proceeding.

We have already discussed how an adapter can accommodate synchronous requests from an integration server to fulfill such a situation. We have also discussed how an adapter can provide event detection within an EIS to asynchronously deliver events to the integration server. The difference here is that we need to facilitate synchronous requests from an EIS to the integration server.

This type of interaction is usually handled through a standards-based interface, such as XML over HTTP, web services, request/reply messaging, CORBA, or those provided for J2EE. Or the integration server may provide direct interfaces for standards-based synchronous requests, bypassing an adapter altogether.

As a consequence, while the WebSphere Business Integration system as a whole provides support for EIS-initiated synchronous request processing across many standard interfaces, only a few of the adapters need to provide this support. These are mainly adapters that support open standards for synchronous processing, and those designed for specific EISs that conform to their proprietary interfaces.

In general, an adapter that provides EIS initiated synchronous request handling may have listeners to receive requests, or it may register itself as a server upon startup to be invoked by clients. When the adapter receives a request, it translates it into a business object, and forwards it to the adapter framework, which submits a synchronous request to the integration server.

When the integration server returns the response business object, the adapter translates it back to the native interface, and provides a synchronous response to the originating client. It is important to note that while not many adapters need to provide this capability, the adapter framework does provide support for this type of interaction between an EIS and the integration server.

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