For example, suppose I want to count the number of currently allocated session beans, and report this count to some GUI in real-time.

I don't want to install, configure and administer a database just so that I can have an Entity Bean to keep track of this count. Plus, it wouldn't exactly fit the bill, since the count should be reset to 0 when the server crashes and comes back up, not restored to its old value.

A Message Bean also sounds too heavy-weight for such a simple task. Plus, what if I want to do something like limit the count to some hard maximum? Suppose I want to put into my session beans' ejbCreate() method something like the following:

			

			if (getSessionCount() > LIMIT) {
			

			throw new RuntimeException( "Connection limit exceeded" );
			

			} else {
			

			incrementSessionCount();
			

			}
			

		

The two *Count() method calls would obviously have to reside within some block that is synchronized on the global count. If I keep the count in a Message Bean, I would have to follow an algorithm kind of like this:

1. MyMessageBean = context.lookup( name );
   

2. 					
   
   					do {
   					
   
   					requestLock( MyMessageBean );
   					
   
   					if (gotLock( MyMessageBean )) {
   					
   
   					break;
   					
   
   					}
   					
   
   					wait for some time (e.g. exponential backoff)
   					
   
   					} while (true);
   				

   
   

3. 					
   
   					if (getSessionCount( MyMessageBean ) > LIMIT) {
   					
   
   					throw new RuntimeException( "Connection limit exceeded" );
   					
   
   					} else {
   					
   
   					incrementSessionCount( MyMessageBean );
   					
   
   					}
   				

   
   
4. releaseLock( MyMessageBean );
   

In other words, "simulate" Java synchronization by using my message bean as a lock manager. But even this is bogus, since what would happen if a bean obtained the lock, then crashed? The message bean would remain locked forever, and the whole application would hang soon thereafter!

Before J2EE, it used to be so simple! I would just have a static counter, and a static lock variable. I would synchronize on the static lock and then do stuff, increment counter, etc. But since J2EE outlawed static variables, it would seem that now such a simple algorithmic requirement cannot be satisfied! Or am I wrong?