Message System Types

Two messaging systems models are in common use.

Publish/Subscribe

A publish/subscribe (pub/sub) messaging system supports an event driven model where information consumers and producers participate in the transmission of messages. Producers "publish" events, while consumers "subscribe" to events of interest, and consume the events. Producers associate messages with a specific topic, and the messaging system routes messages to consumers based on the topics the consumers register interest in.

Point-To-Point

In point to point messaging systems, messages are routed to an individual consumer which maintains a queue of "incoming" messages. Messaging applications send messages to a specified queue, and clients retrieve messages from a queue.

Frequently vendors will support either point-to-point, or publish/subscribe messaging models, or both.

Having looked at message systems in general, we now see how Java developers can take advantage of their power.