EDA Lessons Learned - Content Based Routing

See EDA Lessons Learned for the list

I have found Content Based Routing (CBR) to be helpful in EDA when a sink receives events, processes them, and then produces a subsequent event.

I like CBR because it pulls the routing logic out of the code. The code just processes an XML input and builds an XML output. It does not set the next Topic explicitly. The routing is controlled in the configuration of the sink. This keeps the code simple and reduces coupling. You can also change the routing without changing the code.

We had success using XPath to determine the next Topic. You can use anything in the XML output as part of the next destination. Or you can have several XPath statements building up the next destination based on attributes/elements in the XML. Examples include event type and event status.

I found an article from IBM from way back in 2000 advocating this approach: Using the JMS API and XML in content-based routing. Glad to see I'm so ahead of the times ;)