Tuesday, June 10, 2014

EJB 3.1 Timer Service

We can inject the Timer Service using:

@Resource TimerService timerService;

Then we create the Timer and we can attach an object to it:

public void doSomething(SomeObject obj){
timerService.createTimer(15*60*1000, 15*60*1000, obj);

The createTimer can have 4 different signatures. In the used signature, the first parameter represents the time after which the timeout should be triggered, after the method invocation. The second parameter represents the repetition period and at last, the last parameter is the object that can be attached to this timeout (it must be a Serializable object) The other signatures concerns to a single-event timer with no repetition, by receiving a long value (in miliseconds) or a Date object, and the other concerns to a timer event with repetition, but the first parameter is a Date instead of a long.

When the timer is triggered, it calls the method that is annotated with the @Timeout annotation.

public void methodName(Timer timer){
SomeObject obj = (SomeObject) timer.getInfo();

The signature for the method annotated with the @Timeout annotation must have the following signature:

void <METHOD NAME>(Timer timer)

Accessing the Timer Service
Instead of injecting the Timer Service, we can retrieve it from the Session Context:

@Resource SessionContext ctx;
TimerService service = ctx.getTimerService();

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