How to use @PostConstruct to create timers in a stateless bean EJB3?

Question

I want to create a timer EJB3 when a stateless bean is created in the pool. But if I use @PostConstruct I get the exception:

java.lang.IllegalStateException: [EJB:010193]Illegal call to EJBContext method. The bean is in "null" state. It cannot perform 'getting the Timer Service' action(s). Refer to the EJB specification for more details.

If container calls @PostConstruct, the bean ins't null. So, why I get this exception?

---

CLASS

@Stateless
public class TestBean implements TestLocal {

    @Resource
    TimerService timerService;

    @PostConstruct
    public void startTimer() {
        if (timerService.getTimers().size() == 0) {
            timerService.createTimer(1 * 1000, 1 * 1000, null);
        }
    }

    @Override
    public void test() {        
    }

}

---

INTERFACE

@Local
public interface TesteLocal {

    void test();

}

---

SERVLET

public class TestServlet extends HttpServlet {
    @EJB
    private TestLocal test;

    protected void doGet(....) throws .... {
        test.test();
    }
}

---

DETAILS

I'm using weblogic server 11g.

Quadrumanous

Answer 1

I'm not 100% sure but I think that the bean class must implement javax.ejb.TimedObject or have a method annotated with @Timeout to use EJB timers. Example:

@Stateless
public class TestBean implements TestLocal {

    @Resource
    TimerService timerService;

    @PostConstruct
    public void startTimer() {
        if (timerService.getTimers().size() == 0) {
            timerService.createTimer(1 * 1000, 1 * 1000, null);
        }
    }

    @Timeout
    @TransactionAttribute(value=REQUIRES_NEW)
    public void timeoutCallback(Timer timer) {
        ...
    }

}

Does WebLogic still complain with the above code?

PS: In any case, the error you currently get is very poorly reported, you should probably open a case.

Palate

I follow your example, making 2 changes: a) TestLocal has a method to be implemented by TestBean (without this, weblogic can't deploy) b) a create a servlet that calls the EJB. The error still happens. – Quadrumanous

@Quadrumanous I was really not sure (I'm not even sure that what I suggested is mandatory with EJB 3.0). I may be wrong but this looks like a bug. I suggest contacting the support – Palate

Indeed, this code won't run, as Mike said. Timers can't be accessed or started from a @Postconstruct method. – Groves

Answer 2

You can NOT use a @PostConstruct to create a timer in a stateless bean EJB 3. See this blog How to use EJB 3 timer in a weblogic 10 cluster environment for the explanation. Even the blog was talking about weblogic, but the explanation should apply to other app servers also.

Byre

Yes, same issue occurs in JBoss – Vaporetto

Although this explains why it is not possible, it does not give an actual answer to the question. – Superphosphate

Answer 3

Container will not allow for timerService in method annotated with @PostConstruct of Stateless Session Bean. If you want to use timerService in method annotated with @PostConstruct the go for Singleton session bean(@Singleton).

Cotta