For example, HTTP and JMS are two different transport protocols. If there
was a way to bridge these two, we could leverage the best of both worlds (open
standard nature of HTTP and reliable transport feature of JMS). Typically, it is not
straightforward to connect two different protocols and exchange information. We
need to connect individual, corresponding channels speaking different protocols in
the messaging system. This is demonstrated in the following figure:
Access Web Services Using the JMS Channel
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A protocol bridge can be viewed as a combination of channel adapters. An adapter
can function as a client to the messaging system. With the client role, the adaptor
can invoke application functions through the application supplied interfaces. Thus a
HTTP channel adapter can be used to access the HTTP service and publish messages
on a JMS channel. Similarly, the same adapter can also receive messages from the
JMS channel and invoke the functionality over the HTTP service.
Along those lines, we can now think of a web service adapter to translate between
the HTTP-based web service and the JMS-based messaging system.
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