Chapter 8. JBoss Messaging
This chapter covers
- Understanding messaging systems
- Developing a simple JMS client
- Using message-driven beans (MDB)
- Using message-driven POJOs
- Configuring JBoss Messaging
The previous chapters covered many examples of different types of applications that are deployed to the application server. All the applications have one thing in common—they all use synchronous communications mechanisms to interact with each other. In many cases, this is exactly what you want. For example, it makes no sense to reply to a customer query about how many items are in inventory until the inventory EJB has returned that information.
Sometimes you might prefer to communicate asynchronously with another application or with a component within the same application. For example, standard accounting business practices might require that a log is maintained of certain transactions. You might prefer that the log be written asynchronously so that you don’t hold up the transaction from completing. But you still want a guarantee that the log entry is made. Messaging systems evolved to solve this kind of problem.