Configuring an Enterprise Bean With a Java EE Timer

You can configure the following types of enterprise beans to use a Java EE timer:

• EJB 3.0 stateless session beans and message-driven beans.

• EJB 2.1 stateless session beans, entity beans with container-managed persistence, entity beans with bean-managed persistence, and message-driven beans.

To configure an enterprise bean with a Java EE timer, do the following:

1. Acquire the javax.ejb.TimerService in one of the following ways:

   • For an EJB 3.0 enterprise bean, use the @Resource annotation, as Example 25-1 shows.

   • For an EJB 3.0 or EJB 2.1 enterprise bean, use EJBContext or InitalContext method getTimerService, as Example 25-1 shows.

2. Use TimerService method createTimer to create the appropriate type of timer (see the javax.ejb.TimerService API), as Example 25-1 and Example 25-1 show.

   When you create a Timer on an EJB 2.1 entity bean, the container invokes the timeout callback method of that particular entity bean instance identified by its primary key. Timers created for a particular entity bean are removed when the entity bean is removed.

   When you create a Timer on any other type of enterprise beans, the container invokes the timeout callback method on any instance of that type in the pooled state.

3. Implement a timeout callback method.

   This method must not be static or final and must have the following signature:

   void <METHOD>(Timer timer)
   

   You can implement a timeout callback method in one of the following ways:

   • For an EJB 3.0 enterprise bean, annotate any bean method using the @Timeout annotation, as Example 25-1 shows.

   • For an EJB 3.0 or EJB 2.1 enterprise bean, implement the javax.ejb.TimedObject interface, as Example 25-1 shows.

Example 25-1 Configuring a Java EE Timer on an EJB 3.0 Stateless Session Bean

import javax.ejb.Stateless;
import javax.ejb.TimerService;
import javax.ejb.Timeout;

import javax.ejb.Timer;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;

@Stateless;
public class TimerServiceBean implement MyTimerService {
    // injection of TimerService 
    @Resource TimerService timerService;
    
    // implement bean business interface MyTimerService 
    @TransactionAttribute(value=TransactionAttributeType.REQUIRES_NEW) 
    // default TransactionAttributeType.REQUIRED 
    public void createTimer(Serializable timerInfo) {
        timerService.createTimer(timeout, info);   
    } 

    ...   

    // user annotated timeout method   
    @Timeout   
    @TransactionAttribute(value=TransactionAttributeType.REQUIRES_NEW)   
    public void timeoutCallback(Timer timer) {   
        ...   
    }
}

Example 25-2 Configuring a Java EE Timer on an EJB 2.1 Stateless Session Bean

import java.io.Serializable;
import java.rmi.RemoteException;

import javax.ejb.EJBContext;
import javax.ejb.EJBException;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.ejb.TimedObject;
import javax.ejb.Timer;
import javax.ejb.TimerService;

class ServiceBean_2_1 implements SessionBean, MyTimerService, TimedObject {
    EJBContext ctx;
    
    // implement bean business interface MyTimerService
    public void createTimer(long duration, Serializable info) {
        TimerService timerService = ctx.getTimerService();
        timerService.createTimer(duration, info);
    }
    
    // implement TimedObject
    public void ejbTimeout(Timer timer) {
        System.out.println("Timeout: " + timer.getInfo());
    }

    ...
    // implement SessionBean
    public void setSessionContext(SessionContext ctx) throws EJBException,
                    RemoteException {
        this.ctx = ctx;
    }
}