Ending a thread from jsp

[Lilian Chase]

Hi All,

I am having a problem using Timer and the underlaying TimerThread class.

I'm using a Timer to schedule a routine testing class that runs once every day to test output of the server. The timer is started from a JSP page and can be stopped from the same page.

The problems I'm facing are:
1. When I append the stop=1 as parameter to my JSP URL, the instance of Task class is not the same as the Task instance when I start the timer. Therefore I cannot stop the timer using this method.
2. I can iterate through the Thread in the server to find the underlaying TimerThread invoke by the Timer class. But there is no way to cast it to either Task or Timer class in order to stop the timer. TimerThread is an inner class in Timer, and there's no way for me to set the variables within this class.
3. Is it okay to stop the thread using thread.stop() since I cannot get the class instance to use the volatile variable method.

Currently, I'm considering stopping it using thread.stop() but since this method is deprecated and unsafe, is there any other safer and better methods to use?

The scriptlet in my JSP page to start the timer.

 
<%	
	String start = (String)request.getParameter("start");
        String stop = (String)request.getParameter("stop");
	String time = (String)request.getParameter("time"); 
	TaskTimer task = null;	
	if(start != null) {
		task = new TaskTimer(time, 1);
                task.startTask();
	}
       if(stop != null) {
                task.stopTask();
       }
%>

My TaskTimer Class

public class TaskTimer {
    Timer timer;
    Calendar date;
    long delay;
    public TaskTimer(String time, int mins) {
        delay = 1000L * 60L * mins;
        date = Calendar.getInstance();
        DateFormat sdf = new SimpleDateFormat("HH:mm");
        Date dateToBackup = null;
        try {
            dateToBackup = sdf.parse(time);
        } catch (ParseException e) {
            e.printStackTrace();
        } 
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(dateToBackup);
        date.set(Calendar.HOUR, calendar.get(Calendar.HOUR));
        date.set(Calendar.MINUTE, calendar.get(Calendar.MINUTE));
        date.set(Calendar.SECOND, 0);
        date.set(Calendar.MILLISECOND, 0);  
    }

    public void stopTask() { timer.cancel(); }
    public void startTask() { 
        Calendar currDate = Calendar.getInstance();
        if(currDate.after(date)) {
            date.set(Calendar.DAY_OF_YEAR, date.get(Calendar.DAY_OF_YEAR) + 1);
        }
        timer.scheduleAtFixedRate( new TimerTask() {
		public void run() {
                    System.out.println("Start task");
		}
	}, date.getTime(), delay ); 
    }
}

[Vijitha Kumara]

Every time you accesses the JSP it will create a new instance of the "TaskTimer" class so you don't have access to the one(s) created previously. In order to have one and only one instance you may need to look for the Singleton Pattern

[Lilian Chase]

Hi Vijitha,

Thank you so much for the reply! Using the singleton pattern, I'm able to get the same instance and stop the timer.

Thank you so much!

Another question: Is using Timer or ScheduledExecutorService a better choice?

[Vijitha Kumara]

I would go with the latest one