Styles of messaging in applications

This topic describes the ways that applications can use point-to-point and publish/subscribe messaging. Applications can use the following styles of asynchronous messaging:

Point-to-Point: Point-to-point applications use queues to pass messages between each other. The applications are called point-to-point, because a client sends a message to a specific queue and the message is picked up and processed by a server listening to that queue. It is common for a client to have all its messages delivered to one queue. Like any generic mailbox, a queue can contain a mixture of messages of different types.
Publish/subscribe: Publish/subscribe systems provide named collection points for messages, called topics . To send messages, applications publish messages to topics. To receive messages, applications subscribe to topics; when a message is published to a topic, it is automatically sent to all the applications that are subscribers of that topic. By using a topic as an intermediary, message publishers are kept independent of subscribers.

Both styles of messaging can be used in the same application. Applications can use asynchronous messaging in the following ways:

One-way: An application sends a message, and does not want a response. This pattern of use is often referred to as a datagram .
Request / response: An application sends a request to another application and expects to receive a response in return.
One-way and forward: An application sends a request to another application, which sends a message to yet another application.

These messaging techniques can be combined to produce a variety of asynchronous messaging scenarios. For more information about how such messaging scenarios are used by WebSphere enterprise applications, see the following topics:

For more information about these messaging techniques and the Java Message Service (JMS), see Sun's Java Message Service (JMS) specification documentation (http://developer.java.sun.com/developer/technicalArticles/Networking/messaging/) .

For more information about message-driven bean and inbound messaging support, see Sun's Enterprise JavaBeans specification (http://java.sun.com/products/ejb/docs.html) .

For information about JCA inbound messaging processing, see Sun's J2EE Connector Architecture specification (http://java.sun.com/j2ee/connector/download.html) .

Related tasks
Learning about