Shutdown hook from UNIX

Question

I am trying to get my Java program to exit gracefully on my unix server. I have a jar file, which I start through a cron job in the morning. Then in the evening, when I want to shut it down, I have a cron job which calls a script that finds the PID and calls kill -9 <PID>. However, it doesn't seem that my shutdown hook is activated when I terminate this way. I also tried kill <PID> (no -9) and I get the same problem. How can I make sure the shutdown hook gets called? Alternatively, perhaps there is a better way to kill my process daily.

class ShutdownHook {

    ShutdownHook() {}

    public void attachShutDownHook() {

        Runtime.getRuntime().addShutdownHook(new Thread() {
        @Override
        public void run() {
                System.out.println("Shut down hook activating");
         }
        });
        System.out.println("Shut Down Hook Attached.");
    }   
}

Answer 1

You can use code like this on Unix to trap SIGINT (#2) signal:

Signal.handle(new Signal("INT"), new SignalHandler() {
      public void handle(Signal sig) {
      // Forced exit
      System.exit(1);
   }
});