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"Found two representations of same collection"

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shl

Post subject: "Found two representations of same collection"

Posted: Wed Jun 09, 2004 7:27 am

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

In my current project our team got the following HibernateException "Found two representations of same collection". Could anybody clear me the cause of this exception?

I see the comment to the method that throws this exception:

Code:

/**
 * Initialize the role of the collection.
 *
 * The CollectionEntry.reached stuff is just to detect any silly users who set up
 * circular or shared references between/to collections.
 */
void updateReachableCollection(PersistentCollection coll, Type type, Object owner) throws HibernateException {

   CollectionEntry ce = getCollectionEntry(coll);
      
   if (ce==null) {
      // refer to comment in addCollection()
      throw new HibernateException("Found two representations of same collection");
   }
...
}

Does it mean that an object has two collections with the same JVM idenity or only two equal collections?

Before refactoring everything was fine :). Now going to dig hiberante sources and look what is wrong with our model/logic, but any explanation could help a lot.

Thanks,
one of the silly users (Leonid:)

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shl

Post subject:

Posted: Thu Jun 10, 2004 7:22 am

Expert

Joined: Fri Feb 06, 2004 7:49 am
Posts: 255
Location: Moscow, Russia

answers:

First-level cache (session cache) is implemented using
net.sf.hibernate.util.IdentityMap

Code:

SessionImpl(...)
{
...
    entityEntries = IdentityMap.instantiateSequenced(50);
    collectionEntries = IdentityMap.instantiateSequenced(30);
...}

In the project I found the code similar to the following pseudo-code:

Code:

MyClass obj = (MyClass) session.load(MyClass, id);
// do smth with obj
session.saveOrUpdate(obj); // ERROR!

Solution is obvious: don't do inside one Session session.saveOrUpdate(obj) after the obj was put into the session cache (in my case it was put there by session.load(...)). And session.cear() or session.evict(obj) could help too.

--
Leonid

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