I am working on a warehouse management system, using JPA 2.0 - EclipseLink and I have come across the need to implement concurrent transactions, currently I am implementing a timestamp difference to validate the last time the quantities are altered: added, removed, transferred.
This strategy seems a bit flawed, and requires a lot of manual verification's, that may create bugs, are there alternative methods of doing this that are provided by the JPA framework?
As far as I understand you are trying to implement an optimistic locking strategy with timestamps.
JPA provides out of the box an optimistic locking mechanism with the help of a version field. Basically you have a version field (short, int, long or Timestamp) in your entities that is incremented/set on every modification of the entity.
If an entity has a different version at save time than the version it had at load time an OptimisticLockingException is thrown meaning that another user/thread modified the entity in between. You can catch this exception and decide what do:
It depends on the usecase.
See also: oracle javaee 6 tutorial on optimistic locking
OptimisticLockingException. There's a possibility the bean is managed by a container, or has a remote interface. You might just get a container-initiated ÈJBException, perhaps not even wrapped around the origin. All that is required by the container is to _log_ OptimisticLockingException. If you need this fine grained control, make sure you call the method EntityManager#flush` in a try/catch block at the end of your business logic. If locking fails, you'll catch the OptimisticLockingException for sure and can do whatever you like with it.