Closing Java FileHandler when quitting a routine that runs as a service

Question

I have a little routine that schedules a timer like that:

timer.schedule(new myRoutine(), 1000, 60000);

In the run() method of myRoutine a logger is opened and a FileHandler is attached to it:

FileHandler fh = new FileHandler("app.log"),true);
logger.addHandler(fh);

Since there is no real exit point to the application (as it runs as a service), i have no chance to close and remove the logger´s FileHandler, hence the file lock (app.log.lck) remains, resulting in a new logfile (app.log.1) on next start of the service.

Is there a way to ensure the FileHandler is closed and removed?

Answer 1

You could add shutdown hook like this:

In a method that schedules timer:

public void scheduleFileTask() {
    final FileHandler fh = new FileHandler("app.log"),true);
    Runtime.getRuntime().addShutdownHook(new Thread() {
        @Override
        public void run() {
            fh.close();
        }
    });
    timer.schedule(new MyRoutine(fh), 1000, 60000);
}

And in MyRoutine.java

public class MyRoutine extends TimerTask {
    private final FileHandler handler;

    public MyRoutine(FileHandler hander) {
        this.handler = handler;
    }

    public void run() {
        // use handler here 
        handler.doSomething();
    }
}

For more information you can look up java docs