Question

I have an application that runs in JBoss. I have an incoming web service request that will update an ArrayList. I want to poll this list from another class every 60 seconds. What would be the most efficient way of doing this?

Could anyone point me to a good example?

Answer 1

I would also recommend ScheduledExecutorService, which offers increased flexibility over Timer and TimerTask including the ability to configure the service with multiple threads. This means that if a specific task takes a long time to run it will not prevent other tasks from commencing.

// Create a service with 3 threads.
ScheduledExecutorService execService = Executors.newScheduledThreadPool(3);

// Schedule a task to run every 5 seconds with no initial delay.
execService.scheduleAtFixedRate(new Runnable() {
  public void run() {
    System.err.println("Hello, World");
  }
}, 0L, 5L, TimeUnit.SECONDS);

Answer 2

As abyx posted, Timer and TimerTask are a good lightweight solution to running a class at a certain interval. If you need a heavy duty scheduler, may I suggest Quartz. It is an enterprise level job scheduler. It can easily handle thousands of scheduled jobs. Like I said, this might be overkill for your situation though.

Answer 3

You can use Timer and TimerTask. An example is shown here.

Answer 4

See java.util.Timer. You ll need to start a robot in a separate thread when your app comes up and have it do the polling.

Answer 5

Check the answers to the question "How to run a task daily from Java" for a list of resources related to your problem.

Answer 6

The other answers are basically advising you do your own threads. Nothing wrong with that, but it isn t in conformance with the EJB spec. If that is a problem, you can use JBoss timer facilities. Here is an example of how to do that.

However, if the EJB spec is at issue, storing state like an ArrayList isn t compliant as well, so if you are just reading some static variable anyway, specifically using a container Timer service is likely overkill.

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