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UpAndGone
 Post subject: HTTPSession LazyInitializationException or Illegal attempt..
PostPosted: Fri Nov 10, 2006 3:28 pm 
Newbie

Joined: Tue Nov 07, 2006 5:34 pm
Posts: 3
Hi,

Following the one-session-per-request pattern I have a ServletFilter which closes the session after a request. The session factory uses threadlocal.

I have trouble retreiving a persisted object from HTTPSession. The first exception I encoutered was the LazyInitializationException. Okay, storing the object in one session (i.e. first request) and retreiving its collection in another (i.e. second request) doesn't work.

I need to update the object first. And this is the problem. Calling session.saveOrUpdate(instance) as well as session.lock(instance, LockMode.NONE); results in the following error, if I click on the link multiple times (i.e. having more the one thread accessing the object):

Code:
org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
   org.hibernate.collection.AbstractPersistentCollection.setCurrentSession(AbstractPersistentCollection.java:410)
   org.hibernate.event.def.OnUpdateVisitor.processCollection(OnUpdateVisitor.java:40)
   org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:101)
   org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:61)
   org.hibernate.event.def.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:55)
   org.hibernate.event.def.AbstractVisitor.process(AbstractVisitor.java:123)
   org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:267)
   org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:216)
   org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
   org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
   org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:502)
   org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:494)
   org.hibernate.impl.SessionImpl.saveOrUpdate...

Further reading the documentation and understanding that I can't load two intances of the same object in one session, I figured that I need to call merge() instead. However, doing this brings the LazyInitializationException back into place.

What ist the best strategy to store/load persisted objects in HttpSession?
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baliukas
 Post subject:
PostPosted: Fri Nov 10, 2006 4:22 pm 
CGLIB Developer
CGLIB Developer

Joined: Thu Aug 28, 2003 1:44 pm
Posts: 1217
Location: Vilnius, Lithuania
It is better to store object id in httpsession scope, load object and put it to request scope. If reloading is too slow then use global cache. You can make it transparent for application using httpsession wrapper. It helps to avoid many issues.
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UpAndGone
 Post subject:
PostPosted: Fri Nov 10, 2006 4:52 pm 
Newbie

Joined: Tue Nov 07, 2006 5:34 pm
Posts: 3
I thought about storing the object id and reloading before. I didn't like the idea of just getting an id form httpsession instead of an object (like i used to).

However, I didn't consider writing a wrapper. I think that + caching will fit my needs nicely, thanks!
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