Getting Started with WebSphere Application Server

6
Chapter 6 – Messaging
Messaging is a way to communicate asynchronously, similar to an e-mail system. The
sender creates a message, and sends it to a messaging destination through a messaging
subsystem. The messaging subsystem accepts it for delivery and holds it. The receiver
checks the messaging subsystem to receive the message.
Messaging allows for a loosely coupled solution. The sender application only has to ensure
that the message was accepted for delivery and then can proceed with other processing.
An outage on either the sender or receiver parts, do not immediately affect the entire
system.
Java Message Service (JMS) is used to support messaging in the Java EE world.
In this chapter you will learn about:
• How to configure a JMS resource group
• How to use JMS resources in different applications of Community Edition.
6.1 Community Edition Messaging: The big picture
Figure 6.1 provides an overview on how messaging works in Community Edition. First in
(1), an administrator creates a JMS resource group in the server. Then there are three
ways to use the created JMS resource group:
• In (2a) and (2a.1), the Servlet/jsp uses JNDI lookup or resource injection to get a
reference to the JMS resources, and then uses this reference to send or receive
messages of the JMS resource in the server.
• In (2b) and (2b.1), you can use annotation to specify the JMS queue or topic that the
Message Driven Bean (MDB) listens to. When the message arrives, the MDB will
react according to the content of received message.
• In (2c), a standalone java client (POJO client) can use
ActiveMQConnectionFactory API to get the JMS resource and use the JMS
resource directly.