WebSphere WebSphere Enterprise Service Bus, Version 6.0.1 Operating Systems: AIX, HP-UX, Linux, Solaris, Windows

Working with events

Java objects are used as representations of the Common Base Event specification.

The Common Event Infrastructure represents events as Java objects. Specifically, each event is an instance of a class implementing the org.eclipse.hyades.logging.events.cbe.CommonBaseEvent interface, which is a Java representation of the Common Base Event specification. The org.eclipse.hyades.logging.events.cbe package is part of the Eclipse-based Hyades environment, which is a set of standards and open-source tools for testing, tracing, and monitoring. For more information, see http://www.eclipse.org/hyades/.

The typical life cycle of an event is as follows:

  1. To send an event, an event source creates a new instance of CommonBaseEvent, populates it with property data, and then submits it to an emitter.
  2. The emitter optionally uses the content completion mechanism (if implemented) to populate the event with required property data. The emitter then validates the event and checks it against the currently configured filter criteria. If the event is valid and passes the filter criteria, the emitter sends the event to the event server. For more information about event processing by the emitter, see Sending events.
  3. If persistence is enabled, the event server stores the event in a persistent data store.
  4. If publishing is enabled, the event server publishes the event to one or more Java Messaging Service (JMS) destinations. Event consumers subscribing to these destinations then receive notifications of the new event. The event consumers then use the Notification Helper to convert the received JMS messages back into a CommonBaseEvent instance.

    An event consumer might also submit a query to retrieve the event from the data store. Typically, a consumer uses the query interface to retrieve historical events, especially during startup processing.

    After receiving the event, an event consumer reads the event property data and processes the event.

  5. When it is no longer needed, the event can be purged from the data store.
The Common Base Event specification, which is based on the XML Schema definition language, defines two kinds of event property data:

The CommonBaseEvent interface defines getter and setter methods for each property, as well as helper methods to simplify creation of complex properties. An event source uses the setter methods (or the helper methods) to populate an event with property data before submitting it to an emitter; an event consumer uses the getter methods to retrieve the property data from a received event.

For more information about the XML Schema specification, see http://www.w3.org/XML/Schema.


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Timestamp iconLast updated: 13 Dec 2005
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