[URLyBird]How to check record validity in LockManager's lock()

[Zhixiong Pan]

Hi all,

In LockManager's lock, my while loop is condition on record's validity.But i dont get a good approach to check that validity. I think there should be two ways:

1. add a method isValid() in Data. And in LockManager's lock, call that method.
2. pass a reference of Data to LockManager through constructor, then synchronize and check Data's ioHand.

Which will be better?Thanks very much for your reply.

[Leo Ho]

This's how I implement my lock:

    
public void lock(int recNo, DBMain dataService) {
  while (lockMap.containsValue(recNo)) {
    try {
      lock.wait();
    } catch (InterruptedException ie) {
      log.info("Interrupted exception");
    }
  }
 
  //this call throws RecordNotFoundException
  dataService.read(recNo); 
  lockMap.put(dataService, recNo);
}

HIH.

Leo

[Zhixiong Pan]

Hi Leo,

1. I choose constructor which take charge of getting a reference of Data object(equals your DBMain).

2. Why call dataServeice.read()? Only check the validity！

3. I think you should scan other posts about how to lock in this forum before coding.

[Leo Ho]

Hi Pan, the method signature of my lock() needs to throw RecordNotFoundException (sorry, I didn't remember to type it in the code of the previous post), thus I need to do a read to make sure that the record do exist before trying to insert the lock into the map.

I don't pass DBMain into the constructor since my DBMainImpl is specific for each client while the LogManager must be singleton - by passing it to the method, I can both check the validity and have a unique instance for locking purpose.

Not sure if the read() is what you meant by "validity"???

Leo