Automatic timer @Schedule Java EE

Question

I'm a new user of Java EE and I'm developing an application that has to update weather periodically. I created an automatic timer using the annotation, in order to update every 5 minutes. I would like to change to time dinamically ( an administrator can change it):

@Schedule(minute="*/5",hour = "*", persistent = false)
public void weatherUpdate(){
}

I would need an integer variable called frequency that contains the frequency of weather updates. I tried to do something like this, but this didn't worked:

int freq=5;

@Schedule(minute="*/freq",hour = "*", persistent = false)
public void weatherUpdate(){
}

Do you know any solution?

Answer 1

A possible solution is use a TimerService , for example you can create programmatic timers.

Eg.

@Singleton 
@Startup 
public class ProgrammaticTimer { 

    @Resource 
    TimerService timerService; 

    public void createTimer(String timerId, int frec){ 
        ScheduleExpression expression = new ScheduleExpression(); 
        expression.minute("*/"+freq).hour("*"); 
        timerService.createCalendarTimer(expression, new TimerConfig(timerId, true)); 
    } 

    @Timeout 
    public void execute(){ 
        System.out.println("----Invoked: " + System.currentTimeMillis()); 
    } 
}

To edit a frequency of a timer, first you need cancel the current timer and create new timer with the new value.

Eg.

@Singleton 
@Startup 
public class ProgrammaticTimer { 

    @Resource 
    TimerService timerService; 

    public void createTimer(String timerId, int freq){ 
        ScheduleExpression expression = new ScheduleExpression(); 
        expression.minute("*/"+freq).hour("*"); 
        timerService.createCalendarTimer(expression, new TimerConfig(timerId, true)); 
    } 

    public void editTimer(String timerId, int freq){ 
        cancelTimer(timerId)
        ScheduleExpression expression = new ScheduleExpression(); 
        expression.minute("*/"+freq).hour("*"); 
        timerService.createCalendarTimer(expression, new TimerConfig(timerId, true)); 
    } 

    public void cancelTimer(String timerId) {
        if (timerService.getTimers() != null) {
            for (Timer timer : timerService.getTimers()) {
                if (timer.getInfo().equals(timerId)) {
                    timer.cancel();
                }
            }
        }
    }

    @Timeout 
    public void execute(){ 
        System.out.println("----Invoked: " + System.currentTimeMillis()); 
    } 
}

See also: Using the Timer Service

I hope this help.