I read that we can implement optimistic locking in hibernate using version field using @Version. Then on reading about pessimistic locking, I came to know that org.hibernate.LockMode class which has some options like LockMode.OPTIMISTIC etc which we can specify in session.load().
So my question is do I need to use LockMode.OPTIMISTIC also along with @Version?
Yes. They work together, you can use @Version without LockMode.OPTIMISTIC but you cannot use LockMode.OPTIMISTIC without @Version.
With optimistic locking, whenever you modify an entity then the version column of the entity is incremented. When an entity is saved it ensures that the version column is what it was when the entity was first read and, if not, it throws an OptimisticLockException (which typically results in a restart of the transaction).
There could be times when you need to "change" an entity without really changing it. This tends to be pretty rare. For example, imagine there a Foo object which has a mode field and a Bar object which has a volume field. If the mode is LOUD the volume can be 0-100. If the mode is QUIET the volume can only be 0-10.
It's possible with optimistic locking that you can get in a bad state if one user changes the mode (from LOUD to QUIET) at the same time another user changes the volume (from 5 to 50). This is because the first user increments and checks the version column on the Foo entity and the second user increments and checks the version column on the Bar entity.
One solution for this would be for your changeVolume function to obtain a LockMode.OPTIMISTIC lock on the Foo object. This tells Hibernate that even though this function doesn't modify the Foo object it still needs to increment and check the version field.
