Understanding EJB Timer Services

You can set up a timer that invokes an EJB at a specified time, after a specified elapsed time, or at specified intervals. Timers are for use in modeling of application-level processes, not for real-time events.

Table 2-8 summarizes the timers you can use with enterprise JavaBeans.

Table 2-8 EJB Timers

Timer	Stateful Session Bean	Stateless Session Bean	CMP Entity Bean	BMP Entity Bean	Message-Driven Bean
"Understanding J2EE Timer Services"
EJB 3.0
EJB 2.1
"Understanding OC4J Cron Timer Services"
EJB 3.0
EJB 2.1

For more information, see "Configuring Timer Services".

Understanding J2EE Timer Services

The EJB timer service is a container-managed service that provides methods to allow callbacks to be scheduled for time-based events. The container provides a reliable and transactional notification service for timed events. Timer notifications may be scheduled to occur at a specific time, after a specific elapsed duration, or at specific recurring intervals.The J2EE timer service is implemented by OC4J. An enterprise bean accesses this service by means of dependency injection, through the EJBContext interface, or through lookup in the JNDI namespace.

For more information, see:

Understanding OC4J Cron Timer Services

In the UNIX world, you can schedule a timer, known as a cron timer, to execute regularly at specified intervals. Oracle has extended OC4J to support cron timers with EJBs. You can use cron expressions for scheduling timer events with EJBs deployed to OC4J.

For more information, see "Configuring an EJB with an OC4J Cron Timer".