Runnable classes

[tmiranda]

Before I start banking my head against the wall in trying to figure out how to get a runnable class to work I'm hoping to get answers to some very basic questions. Help greatly appreciated.

Can somebody confirm that the general stun of the code should look like this:

public class MyClassName implements Runnable {

     public void run () {

     }

}

It seems too easy, so I know I'm missing something Anything special needed in run()?

For my purposes I want the thread to stay alive as long as the sage server is running. Is it safe to create an endless loop (it will sleep for long periods of time) or do I need to put in some type of checks for sage shutting down?

Do I need to do anything special in the IDE (NetBeans) or do I just compile the code like a normal .JAR file?

[PLUCKYHD]

Looks okay you need a stop() as well so it knows what to do when it stops.

I sleep then loop repeat. Sean prefers timers which work as well. I found sleeping works pretty well and it acceptable.

Just make sure and catch your exceptions and do something with them.

Also I prefer to make it a Deamon thread so it gets lower priority and doesn't stop sage from shutting it down if the service is stopped.

[stuckless]

Tom, if you are going to create a thread that basically "polls" every n # of seconds, then I'd suggest you take advantage of the Java Timer and TimerTask classes. These are there to simplify your dealing with threads, etc, for the simple purpose of polling.

Timer timer = new Timer();
TimerTask mytask = new TimerTask() {
    public void run() {
        // do your work
    }
};
timer.scheduleAtFixedRate(mytask, 0, 60*1000); // repeats every 60 seconds, starts immediatly

EDIT: Looks like I'm getting predictable Plucky is predicting my responses now

[Slugger]

Don't worry about the stop() method, it'll never be called. That method's long since been deprecated because it can cause deadlock. If you're going to go with the work, sleep, work loop, it should look something like this:

public void run() {
   while(true) {
      // Do your work
      try {
         Thread.sleep(300000); // Sleep for 5 mins
      } catch(InterruptedException e) {
         e.printStackTrace(); // Log who killed your thread, if you like
         Thread.currentThread().interrupt(); // Make sure outer loops also get the signal (not necessary in this example, but never a bad idea)
         break; // Exit the while loop
      }
   }
}

So your thread will run until someone interrupts (presumably, that'll be the Sage core at Sage shutdown).

[tmiranda]

I created a basic runnable class that just prints a line to the sage log and, much to my amazement, it worked on the first try. It just goes to show you that even a blind squirrel finds a nut every once in a while.

Plucky - I'm not sure I know what you mean by needing a stop(). When Sage ends I want the runnable class to end. The thread will not have to do anything special. What would normally be done by stop()?

Why does the runnable class stop sage from shutting down? (i.e. Why do I need a daemon thread?)

Thanks for the info on catching exceptions. I haven't done that yet so I guess it's about time I learned how....

Sean - It doesn't really "poll". It sleeps for several hours and then wakes up to do some work, then goes back to sleep. It should do this as long as the sage server is up and running.

The "work" it does is to look for favorite podcasts and then if they need to be downloaded, send a message to my servlet that will download them.

Using timers seems straight forward (famous last words) so I'll go down that path if it's better than looping and sleeping.

[tmiranda]

Slugger - Thanks for the info. I think we were both typing at the same time.

[stuckless]

Originally Posted by tmiranda

Using timers seems straight forward (famous last words) so I'll go down that path if it's better than looping and sleeping.

Basically the timers do the looping and sleeping for you