The covenant usually
implements a content-based router. A content-based router is used to route each
message to the correct recipient based on the message content. The routing can be
based on a number of criteria such as the existence of a version parameter and the
version info in targetNamespace,. The advantage of the covenant approach is that
Consumers are unaware that multiple service versions coexist at the Provider's end.
Hence they needn't adjust their address to route to specific service versions. Instead,
they will place their version flag in the message and send it to the same address. It is
up to the covenant to redirect the message to the appropriate version of the service.
Multiple Endpoint Addresses
In the Multiple Endpoint Address approach, each version of the web service
is allotted a separate endpoint address, and they are then bound to a look up
mechanism like a registry. Now, the Consumer has to decide the endpoint address
for service invocation by looking at the Service Registry, and cross matching the
version of interest. Then the Consumer sends messages to the selected endpoint
address of interest.
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