Java EE 6 - Part 6 - Writing EJB TimerService and Interceptors

Project: EJB31-Common


package helloworld.beans;

import javax.ejb.Remote;
import javax.ejb.Timer;

/**
 * Interface to manage the EJB timer service.
 *
 * @author rwatsh
 */
@Remote
public interface AutomaticManagerBeanRemote {
    public void manageTimer(int interval, int threshold);

    void monitorAutomaticTimer(Timer timer);
}

Project:EJB31-ejb


package helloworld.beans;

import javax.annotation.Resource;
import javax.ejb.EJB;
import javax.ejb.Stateless;
import javax.ejb.Timeout;
import javax.ejb.Timer;
import javax.ejb.TimerService;

/**
 * Bean implementation for controlling the timer service EJB.
 *
 * @author rwatsh
 */
@Stateless
public class AutomaticManagerBean implements AutomaticManagerBeanRemote {
    @EJB
    private AutomaticSayHelloBean automaticSayHelloBean;
    @Resource
    private TimerService timerService;
    private int threshold;
 
    @Override
    public void manageTimer(int interval, int threshold) {
        this.threshold= threshold;
        int currentCount = automaticSayHelloBean.getNotificationCount();
        if (currentCount >= threshold){
            automaticSayHelloBean.cancelTimer();
        } else {
            timerService.createIntervalTimer(interval, interval, null);
        }
    }
 
 

    // Add business logic below. (Right-click in editor and choose
    // "Insert Code > Add Business Method")

    @Override
    @Timeout
    public void monitorAutomaticTimer(Timer timer) {      
        int currentCount = automaticSayHelloBean.getNotificationCount();
        if (currentCount >= threshold) {
            automaticSayHelloBean.cancelTimer();
            timer.cancel();
        }
    }

}

-------------------------

package helloworld.beans;

import helloworld.interceptors.PMInterceptor;

import helloworld.vo.GreetingRequest;

import javax.ejb.EJB;

import javax.ejb.Singleton;

import javax.ejb.LocalBean;

import javax.ejb.Schedule;

import javax.ejb.Startup;

import javax.ejb.Timer;

import javax.interceptor.Interceptors;

/**

 * This is a stateless bean using EJB timer service.

 *

 * @author rwatsh

 */

@Singleton

@LocalBean

@Startup

public class AutomaticSayHelloBean {

    @EJB

    private SingletonHelloWorldBean singletonHelloWorldBean;

    private int timerNotifications;

    private boolean cancelTimer = false;

    // Add business logic below. (Right-click in editor and choose

    // "Insert Code > Add Business Method")

    /**

     * Using schedule will cause a timer notification to occur every 5 seconds.

     */

    @Interceptors(PMInterceptor.class)

    @Schedule(second = "*/5", minute = "*", hour = "*")

    public void sayHello(Timer timer) {

        if (!cancelTimer) {

            GreetingRequest request = singletonHelloWorldBean.sayHello();

            System.out.println("AutomaticSayHelloBean.sayHello:- " + request);

            timerNotifications++;

        } else {

            timer.cancel();

            System.out.println("AutomaticSayHelloBean.sayHello: canceled timer");

        }

    }

    public int getNotificationCount() {

        return timerNotifications;

    }

    public void cancelTimer() {

        this.cancelTimer = true;

    }

}

---------------------

package helloworld.interceptors;

import javax.interceptor.AroundTimeout;

import javax.interceptor.InvocationContext;

/**

 * Interceptor to monitor invocations of a method.

 *

 * @author rwatsh

 */

public class PMInterceptor {

    private long numberOfInvocations;

    @AroundTimeout

    public Object monitorInvocations(InvocationContext ic) throws Exception {

        try {

            Object returnValue = ic.proceed();

            numberOfInvocations++;

            System.out.println("PMInterceptor.monitorInvocations: invocation count -" + numberOfInvocations);

            return returnValue;

        } catch (Exception ex) {

            System.err.println("PMInterceptor.monitorInvocations: error occurred -" + ex);

        }

        return null;

    }

}

------------------------

Project: EJB31-app-client

package ejb31;

import helloworld.beans.AutomaticManagerBeanRemote;

import javax.ejb.EJB;

/**

 * Test the automatic timer bean through its session facade

 * AutomaticManagerBean.

 *

 * @author rwatsh

 */

public class MaMApp {

    @EJB

    private static AutomaticManagerBeanRemote automaticManagerBean;

    /**

     * @param args the command line arguments

     */

    public static void main(String[] args) {

        automaticManagerBean.manageTimer(1000 * 60, 50);

        System.out.println("MaMApp.main: started management process");

    }

}

Output:

INFO: TimeBasedHelloWorldBean.postConstruct

INFO: SingletonHelloWorldBean.postConstruct

INFO: AutomaticSayHelloBean.sayHello:- helloworld.vo.GreetingRequest [requestTime=3/15/13 10:49 AM, greeting=Good Morning]

INFO: PMInterceptor.monitorInvocations: invocation count -1

INFO: AutomaticSayHelloBean.sayHello:- helloworld.vo.GreetingRequest [requestTime=3/15/13 10:49 AM, greeting=Good Morning]

INFO: PMInterceptor.monitorInvocations: invocation count -2

INFO: AutomaticSayHelloBean.sayHello:- helloworld.vo.GreetingRequest [requestTime=3/15/13 10:49 AM, greeting=Good Morning]

INFO: PMInterceptor.monitorInvocations: invocation count -3

.....

INFO: helloworld.beans.SingletonHelloWorldBean: @PreDestroy