Question

I have java-servlet application +hibernate + streaming server

Flow:

1. user login begin video streaming
2. decrement abonament minutes in data base every 2 seconds
3. if minutes < 0 send request for the new minutes(response may be after
   long time, if so continue decrement )

Problem:

Appears data consistency problem, other words while decrementing minutes,
ex: user.setMinutes(user.getMinutes() - 2) may not see changes maded by new minutes response, and minutes will be corrupted

I thought sollution could be create new hibernate transaction and commit it every time when I change minutes, but this didn’t worked:

Transaction t = session.beginTransaction();
user.setMinutes()
session.flush();
t.commit();

Question:

How to solve this problem, when each change get most recent data?

Answer 1

The Hibernate session caches your entities in memory (in your case the User entity). It’s not enough to create a new transaction for changing the remaining minutes, you also have to reload the changes made by other tasks (addditional minutes request). You can achieve this by calling refresh():

session.refresh(user);
user.setMinutes(user.getMinutes() - 2);
session.flush();