Question

I am using hibernate and Spring to control the transactions.

I currently have a Object Foo that I want to read from database before I update it. Something like that

@Transactional(isolation = Isolation.READ_COMMITTED)
public void update(Foo beingUpdated) {
   Foo beforeUpdate = fooDao.read(beingUpdated.getId());

   checkDifferences(beingUpdated, beforeUpdate);
   fooDao.update(beingUpdated);
}

but my problem is that when I read Foo, the returned object is the one being updated, not the commited. Am I misunderstanding the use of Isolation? How can I read the object committed at database, not the one being updated?

Appreciate any help.

Answer 1

Here are some options for you:

1. Re-read the entity in another session, perhaps using a method annotated with @Transactional(propgation=REQUIRES_NEW) which will give you a new session for that method. This adds DB overhead though: you will need to re-load the entity.
2. Delve into the Hibernate internals using something like PostUpdateEvent.getOldState().
3. Save off the state you’re interested in with a LoadEventListener. If you put the information into transient fields you can access it later.

None of these options are very palatable, but I have used 1 and 3 successfully in a few places.