2.5.4 Scheduling

The timer service is a notification broadcaster that sends notifications at specific dates and times. The timer service provides a scheduling mechanism that can be used to trigger actions in the listeners. Timer notifications can be single events, repeated events, or indefinitely repeating events. The timer notifications are sent to all of the service's listeners when a timer event occurs.

The timer service manages a list of dated notifications, each of which has its own schedule. Users can add or remove scheduled notifications from this list at any time. When adding a notification, users provide its schedule, defined by the trigger date and repetition policy, and information that identifies the notification to its listeners. The timer service uses a single Java thread to trigger all notifications at their designated time.

You can stop the timer service to prevent it from sending notifications. When you start it again, notifications that could not be sent while the timer was stopped are either sent immediately or discarded, as determined by the configuration of the service.

Like all other agent services, the timer is implemented as an MBean so that it can be registered in an agent and configured by remote applications. However, the timer MBean can also be used as a stand-alone object in any application that needs a simple scheduling service.

For more information about the timer service, see the JMX specification document.