An event consumer is any application that receives events
from the event server.
An event consumer might be an application that receives asynchronous
event notifications, or it might be an application that queries and processes
historical event data from the persistent data store. The event consumer receives
events in the form of Java objects; it can then use the CommonBaseEvent interface
to retrieve event property data, or convert the event to another supported
format (such as XML) for forwarding to another application.
An event consumer can receive events in either of two ways:
- It can use the Java Messaging Service (JMS) interface to
subscribe to a queue or topic, receiving event notifications asynchronously
as JMS messages. This is the most efficient approach for an event consumer
that needs to process new and changed events as they arrive at the event server.
- It can use the Event Access interface to query historical events from
the persistent data store, retrieving the requested events synchronously.
This is useful for startup processing; by querying the data store for historical
events, an event consumer can determine current state information before beginning
to receive new events through JMS.
In addition to receiving events, an event consumer can also modify events,
delete events, and purge old events from the data store.