As On Message handlers are used within asynchronous processes, it is necessary to
specify the correlations used so that the input message can be applied to the correct
instance of the running BPEL process. When many instances of the same process
are running within the BPEL engine, the engine uses correlations to link together
messages from clients to specific instances of running processes. A correlation set
is basically a unique piece of information passed from the client to the BPEL engine
that can be used to uniquely tie client messages to a running process. A correlation
set is rather like a prime key in a relational database. It can contain one piece of
data just like the prime key of a database table, or it can consist of multiple pieces
of data like a compound key. In this case, the combination of all the data within the
correlation set makes up the unique identifier for the process.
Correlation sets can be created within NetBeans by right-clicking on the BPEL
process within the Design view and selecting the Add | Correlation Set??¦ menu
option. On the resulting dialog, we can select the name we wish to give to the
correlation set and define which properties from the WSDL file we wish to use to
define the set.
Handling Events
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The correlations tab of the Property Editor allows us to specify which correlation set
we wish to use for the specific On Message handler.
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