I'm facing a problem i think alot of people faced it.

The problem that i have a table Account and a lot of transaction done on this table update and read so i got inconsistent data problem "two transaction read the account balance the first one commit and update the balance so the second one have a wrong balance now!!"
so i need to lock the object on the transaction and any other transaction wants to acquire that object lock
and exception must be thrown.

I know that there are two ways of locking and i preferred to use pessimistic but no exception is thrown if another transaction tried to acquire that lock.