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An event queue is an event-based publish-subscribe solution for the application information delivery and messaging. It provides asynchronous communication for different modules/roles in a loosely-coupled and autonomous fashion.

By publishing, a module (publisher) sends out messages without explicitly specifying or having knowledge of intended recipients. By subscribing, a receiving module (subscriber) receives messages that the subscriber has registered an interest in, without explicitly specifying or knowing the publisher. Eventqueue-concept.jpg

ZK generalizes the event queue to support the server push. The use is straightforward: specifying the scope of a given event queue as EventQueues.APPLICATION (or EventQueues.SESSION, but rare). For example,

EventQueue que = EventQueues.lookup("chat", EventQueues.APPLICATION, true);

For more information about event queues, please refer to the Event Handling: Event Queues section.

For the information about low-evel API, please refer to Asynchronous Tasks section, if the task can execute asynchronously; or Synchronous Tasks if it must execute synchronously.

Version History

Last Update : 2011/7/26

Version Date Content
5.0.6 November 2010 The event queue won't start any working threads and they are serializable, so it is safe to use them in a clustering environment.

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