PaaS Partner Community

  • August 8, 2014

Message Correlation using JMS by Martien van den Akker

Juergen Kress
PaaS Partner Adoption

Last year I created a few OSB services with the asynchronous request response message exchange pattern. OSB does not support this out of the box, since OSB is in fact synchronous in nature. Although OSB supports the WS - Addressing namespaces, you need to set the WS-Addressing elements programmatically.

Since OSB is synchronous the request and response flows in the Asynchronous Request/Response pattern are completely seperated implemented from eachother. That means that in the response flow you don't know what request message was responsible for the current response. Even worse: you don't know what client did the request and how to respond to that client in a way you can correlate to the initating instance. Using SOA/BPM Suite as a client, you want to correlate to the requesting process instance.

There are of course several ways to solve this. I choose to use a Universal Distributed Queue for several reasons, where knowledge of JMS and performance were a few. I only need to temporarly store a message against a key. Coherence was not on my CV yet. And a database table requires a database(connection) with the query-overhead, etc.

Unfortunately you can't use the OSB transports or SOASuite JMS adapters to get/browse for a message using a correlation-id in a synchronous way. When you create a proxy service on a jms transport or configure a JMS Adapter for read it will be a polling construction. But it's quite easy to do it in Java, so I created a java-method to get a message based on a CorrelationId.

One thing I did not know back then was that if you put a message on the queue from one OSB Server Node (having a JMS Server) it can't be read from the other node, as such. Messages are stored in the local JMS Server member of the Queue.

I found that you can quite easily reach the local member of a Universal Distributed Queue on a certain JMSServer on Weblogic by prefixing the JNDI name of the queue with the JMSServer separated with the at-sign ('@'): Read the complete article here.

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