WebSphere Business Integration Adapters: An Adapter Development and WebSphere Business Integration Solution

146 WebSphere Business Integration Adapters

sequential event processing request is received, this method is called to

undertake the interaction with the adapter. This action is typically known as

callback, because the communication code must callback into the adapter to

interact with the framework and ultimately the broker. Although it is possible to

embed all functionality within the communication code, you would still need to

call all WebSphere Business Integration Adapter Framework code through a

callback to methods that were inherited by the custom connector agent class.

What does it mean to develop a custom adapter? The following are two cases

that use different technologies to call the executeCollaboration method:

 Case 1: Interacting with a back-end application with RMI

Within this scenario, the back-end application is capable of issuing RMI calls

to an adapter that then issue the executeCollaboration method to process

the synchronous event request.

 Case 2: Interacting with a back-end application with TCP/IP sockets

With any TCP/IP sockets transport, there are multiple ways of interacting with

the back-end application. For simplicity, we assume that the adapter opens a

separate server socket to handle synchronous event requests from the

back-end application.

9.3 Single or multithreaded support for sequential event

processing

When designing the sequential event processing mechanism for a custom

adapter, you must understand the back-end application requirements. Will the

application only make sequential event requests serially, or will the application

require the custom adapter to process multiple sequential events concurrently?

Fortunately, beyond potentially making the development of the communication

code more complex, multithreaded support is available.

Returning to our previous two scenarios, using RMI as the transport mechanism

provides multithreaded support automatically, because each call into the RMI

stub runs on a thread that is created by the RMI. So, if you were to make

simultaneous multiple calls to the sequential event processing, RMI would start

multiple threads automatically to concurrently process the request. Within

Note: We do not recommended that you call the executeCollaboration

method from within an event processing mechanism, because this method is

synchronous and blocks the event processing until a response is received.