public static  void processReachableCollection(PersistentCollection collection,
    CollectionType type,
    Object entity,
    SessionImplementor session) throws HibernateException 
{
		collection.setOwner(entity);
		CollectionEntry ce = session.getPersistenceContext().getCollectionEntry(collection);
		if ( ce == null ) {
			// refer to comment in StatefulPersistenceContext.addCollection()
			throw new HibernateException(
					"Found two representations of same collection: " +
					type.getRole()
			);
		}
		// The CollectionEntry.isReached() stuff is just to detect any silly users  
		// who set up circular or shared references between/to collections.
		if ( ce.isReached() ) {
			// We've been here before
			throw new HibernateException(
					"Found shared references to a collection: " +
					type.getRole()
			);
		}
		ce.setReached(true);
		SessionFactoryImplementor factory = session.getFactory();
		CollectionPersister persister = factory.getCollectionPersister( type.getRole() );
		ce.setCurrentPersister(persister);
		ce.setCurrentKey( type.getKeyOfOwner(entity, session) ); //TODO: better to pass the id in as an argument?
		if ( log.isDebugEnabled() ) {
			log.debug(
					"Collection found: " +
					MessageHelper.collectionInfoString( persister, ce.getCurrentKey(), factory ) +
					", was: " +
					MessageHelper.collectionInfoString( ce.getLoadedPersister(), ce.getLoadedKey(), factory ) +
					( collection.wasInitialized() ? " (initialized)" : " (uninitialized)" )
			);
		}
		prepareCollectionForUpdate( collection, ce, session.getEntityMode(), factory );
}

Initialize the role of the collection.

 public static  void processUnreachableCollection(PersistentCollection coll,
    SessionImplementor session) throws HibernateException 
{
	                   	 
		if ( coll.getOwner()==null ) {
			processNeverReferencedCollection(coll, session);
		}
		else {
			processDereferencedCollection(coll, session);
		}
}

record the fact that this collection was dereferenced