SEs can integrate Java-based applications (and other resources), or
applications with available Java APIs.
Service Engine is a component which provides (and consumes) business
logic and transformation services to other components. There are
various Service Engines available, such as the BPEL service engine
for orchestrating business processes, or the Java EE service engine for
consuming Java EE Web Services. We will discuss some of the more
common Service Engines later in this chapter.
Service Engines
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The Normalized Message Router
As we can see from the previous figure, SE's don't communicate directly with each
other or with the clients, instead they communicate via the NMR. This is one of the
key concepts of JBI, in that it promotes loose coupling of services.
So, what is NMR and what is its purpose? NMR is responsible for taking messages
from clients and routing them to the appropriate Service Engines for processing.
(This is not strictly true as there is another standard JBI component called the Binding
Component responsible for receiving client messages. Binding Components are
discussed in Chapter 4. Again, this further enhances the support for loose coupling
within JBI, as Service Engines are decoupled from their transport infrastructure).
NMR is responsible for passing normalized (that is based upon WSDL) messages
between JBI components.
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