事务内的org.hibernate.LazyInitializationException

Question

Currently using slightly older Hibernate (3.3.2.GA) - and getting org.hibernate.LazyInitializationException within Transaction boundaries. I confirmed that the calling method is marked @Transactional , plus stack trace at the time of exception is showing it too: org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)

Still, an attempt to iterate over @CollectionOfElements promptly throws the LazyInitializationException with " no session or session was closed ".

While debugging it, I see that Hibernate proxy on the relevant collection has a session of null virtually as soon as it is loaded by Hibernate. Is that something to worry about? How can I track this down and resolve it - in other words, while debugging, what's the best way to track down what is happening to the session?

Obviously I understand that changing the collection to Eager fetching will resolve the issue, but I rather figure out why Lazy Load is not working since this (potentially) large collection is not needed in most scenarios.

Thank You!

Answer 1

adir1 I had exactly the same problem. In my case the issue was caused by the fact that the instance which contained the lazy-loaded collection had been manually evicted before (all within transaction boundaries).

Answer 2

Regarding the age of this question, for posterity:

The same problem happened for me because I kept entities cached in memory. The exception was thrown as soon as accessing those entities in a later transaction - different from the one during which the entities were first collected. Hence the lost session problem.

Solved by setting up proper 2nd level caching.

Answer 3

My guess is that when you return from the method fetching the entity and start iterating through it you're already at different transactional contexts, thus leading to the lazy initialization problem; if you're using a DAO try setting both of these methods to the same transaction (ie setting them as REQUIRED).

I might be totally mistaken though. I've just tested this with EJB3 + JPA and got the lazy initialization problems you described when the method fetching the entity was at a different transactional context.

EDIT: Like baba said in his comment, a better solution would be either eager fetching through HQL / Criteria (fetch join clause in HQL) or, less preferably, using Hibernate.initialize before returning it.