When is messaging (e.g. JMS) an alternative for multithreading?

Question

I work on a data processing application in which concurrency is achieved by putting several units of work on a message queue that multiple instances of a message driven bean

Answer 1

In an EJB container, actually, there is no alternative, since you're not allowed to create your own threads in an EJB container. JMS is doing all of that work for you, at a cost of running it through the queue processor. You could also create a Java Connector, which has a more intimate relationship with the container (and thus, can have threads), but it's a lot more work.

If the overhead of using the JMS queue isn't having a performance impact, then it's the easiest solution.