取消部署应用程序时，计时器Java不会停止在Netbeans中显示结果吗？

Question

I do create a timer which start when i deploy my application, what i note is this timer not stop when i Undeploy my application?

1. How can this happen, and show me the result in Output netbeans?
2. Should i restart my server every time that i Undeploy my application?

Singleton

@Singleton
@Startup
public class StartWhenDeploy {

    private static final int PERIOD = 3000;

    @PostConstruct
    public void init() {
        System.out.println("I will set information to start my task");
        Timer timer = new Timer();
        timer.schedule(new TimerAction(1), new Date(), PERIOD);
    }
}

TimerTask

public class TimerAction extends TimerTask {

    public int nbrUsers;

    public TimerAction(int nbrUsers) {
        this.nbrUsers = nbrUsers;
    }

    @Override
    public void run() {
        System.out.println("This task is planified to execute at " + new Date());
        System.out.println("Creation " + (createUser() ? "------------Success------------" : "------------Failed------------"));
    }

    public boolean createUser() {
        try {
            System.out.println("-------------->" + nbrUsers);
            for (int i = 0; i < nbrUsers; i++) {
                System.out.println("Create user >>>>" + i);
            }
            return true;
        } catch (Exception e) {
            System.out.println("Exception " + e);
            return false;
        }
    }
}

It still show me the result like this in Output netbeans :

...
Infos: This task is planified to execute at Wed Nov 16 14:40:29 GMT+01:00 2016
Infos: -------------->1
Infos: Create user >>>>0
Infos: Creation ------------Success------------
...

Someone have an idea about this issue?

Thank you.

Answer 1

TimerTask spawns a new thread whose lifecycle is unaffected by undeploying your application.

A better way to do this would be to use a proper EJB timer with @Schedule like this example :

@Singleton
@Startup
public class SimpleTimerBean {

    static Logger logger = Logger.getLogger(SimpleTimerBean.class.getCanonicalName());

    @Schedule(hour = "*", minute = "*", second = "*/3", info = "Create user every 3 seconds", timezone = "UTC")
    public boolean createUser() {
        try {
            System.out.println("-------------->" + nbrUsers);
            for (int i = 0; i < nbrUsers; i++) {
                System.out.println("Create user >>>>" + i);
            }
            return true;
        } catch (Exception e) {
            System.out.println("Exception " + e);
            return false;
        }
    }
}

Answer 2

In GlassFish (in JavaEE in general), you should use the TimerService from the EJB specification for scheduling. I assume you are using java.util.Timer , which just runs in a separate thread. GlassFish does not know anything about the thread, so it cannot stop it with undeploy.

You should rewrite your Singleton to something like this:

@Singleton
@Startup
public class StartWhenDeploy {

    private static final int PERIOD = 3000;

    // Inject the TimerService into this EJB
    @Resource
    private TimerService timer;

    private TimerAction action;

    @PostConstruct
    public void init() {
        System.out.println("I will set information to start my task");
        // the action object is created before the timer
        action = new TimerAction(1);
        timer.createTimer(new Date(), PERIOD, "My timer");
    }

    // this method will be executed when the timer fires - it needs to wrap your `TimerAction` created once per this singleton instance (`TimerAction` does not have to extend `TimerTask` now)
    @Timeout
    public void runTimerAction() {
        action.run();
    }

}