To create a timer, the bean invokes one of the createTimer methods of the TimerService interface. (For details on the method signatures, see the TimerService API documentation at http://java.sun.com/javaee/5/docs/api/javax/ejb/TimerService.html.) When the bean invokes createTimer, the timer service begins to count down the timer duration.
The bean described in The timersession Example creates a timer as follows:
Timer timer = timerService.createTimer(intervalDuration, "Created new timer");
In the timersession example, createTimer is invoked in a business method, which is called by a client.
Timers are persistent. If the server is shut down (or even crashes), timers are saved and will become active again when the server is restarted. If a timer expires while the server is down, the container will call the @Timeout method when the server is restarted.
The Date and long parameters of the createTimer methods represent time with the resolution of milliseconds. However, because the timer service is not intended for real-time applications, a callback to the @Timeout method might not occur with millisecond precision. The timer service is for business applications, which typically measure time in hours, days, or longer durations.