The scenario is simple: a system, as part of its business logic, makes a request to something, and expects a response within 2 seconds (or minutes or days or whatever). If the response is not received, the system must alert an operator.

How do I implement this timer within the J2EE framework?

Have you considered using a JMS service call? I think it is possible to specify a timeout for synchronous calls, which may be exactly what you are looking for.

I do not this it has anything to do with J2EE. In your monitoring application you just implement timeout mechanism and use it to see if the application responds in a timely manner, for example:

  TimedOp op = new CheckSomeFunction(...);
  if(!op.do(2000) {
    ... alert operator here ...
  }

abstract class TimedOp implements Runnable {
  private boolean done = false;
  ...
  public boolean do(timeout) throws InterruptedException {
    boolean ok = false;
    (new Thread(this)).start();
    synchronized(this) {
      if(done) {
        ok = true;
      } else {
        wait(timeout);
        ok = done;
      }
    }
    return ok;
  }

  public void run() {
    doStuff();
    synchronized(this) {
      done = true;
      notify();
    }
  }

  // to be implemented by the user
  public abstract void doStuff();
}

Note, use of thread synchornization is strictly forbidden in EJB. So you cannot use the above approach in a portable way. I reccomend a synchornous JMS call with a timeout.

Dave Wolf
Internet Applications Division
Sybase

When you say "a system, as part of its business logic, makes a request to something, and expects a response within 2 seconds", who is making the asynchronous request? The client or an EJBean?

In either case, to make asynchronous requests and callbacks involving EJBs, you CANNOT use a timer! Plain EJBs are simply synchronous; to make EJBs asynchronous you either have to spice it up with JMS or use EJB 2.0 MessageBeans.

Gene Chuang
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