How to lock and reload an entity correctly

Question

In my web application I have several threads that potentially access the same data concurrently why I decided to implement optimistic (versioning) and pessimistic locking with Hibernate.

Currently I use the following pattern to lock an entity and perform write operations on it (using Springs Transaction manager and transaction demarcation with @Transactional):

@Transactional
public void doSomething(entity) {
    session.lock(entity, LockMode.UPGRADE);
    session.refresh(entity);

    // I change the entity itself as well as entites in a relationship.
    entity.setBar(...);
    for(Child childEntity : entity.getChildren()) {
        childEntity.setFoo(...);
    }
}

However, sometimes I am getting StaleObjectException when the @Transactional is flushing that tells me that a ChildEntity has been modifed concurrently and now has a wrong version.

I guess I am not correctly refreshing entity and its children so I am working with stale data. Can someone point out how to achieve this? Some thoughts of me included clearing the persistence context (the session) or calling session.lock(entity, LockMode.READ) again, but I am not sure what is correct here.

Thanks for your help!

Answer 1

You may want to take at look at this Hibernate-Issue: LockMode.Upgrade doesn't refresh entity values.

In short: Hibernat does NOT perform a select after a successful lock if the given entity was already preloaded. You need to call refresh for the entity for yourself after you received the lock.