Examples of org.hibernate.collection.spi.PersistentCollection

org.hibernate.collection.spi.PersistentCollection
Persistent collections are treated as value objects by Hibernate. ie. they have no independent existence beyond the object holding a reference to them. Unlike instances of entity classes, they are automatically deleted when unreferenced and automatically become persistent when held by a persistent object. Collections can be passed between different objects (change "roles") and this might cause their elements to move from one database table to another.

Hibernate "wraps" a java collection in an instance of PersistentCollection. This mechanism is designed to support tracking of changes to the collection's persistent state and lazy instantiation of collection elements. The downside is that only certain abstract collection types are supported and any extra semantics are lost

Applications should never use classes in this package directly, unless extending the "framework" here.

Changes to structure of the collection are recorded by the collection calling back to the session. Changes to mutable elements (ie. composite elements) are discovered by cloning their state when the collection is initialized and comparing at flush time. @author Gavin King


  @Override
  public void execute() throws HibernateException {
    // this method is called when a new non-null collection is persisted
    // or when an existing (non-null) collection is moved to a new owner
    final PersistentCollection collection = getCollection();
    
    preRecreate();


    getPersister().recreate( collection, getKey(), getSession() );

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          //    with the current Session
          //throw new AssertionFailure("bug loading unowned collection");
        }
      }


      PersistentCollection rowCollection = persistenceContext.getLoadContexts()
          .getCollectionLoadContext( rs )
          .getLoadingCollection( persister, collectionRowKey );


      if ( rowCollection != null ) {
        rowCollection.readFrom( rs, persister, descriptor, owner );
      }


    }
    else if ( optionalKey != null ) {
      // we did not find a collection element in the result set, so we

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          //    with the current Session
          //throw new AssertionFailure("bug loading unowned collection");
        }
      }


      PersistentCollection rowCollection = persistenceContext.getLoadContexts()
          .getCollectionLoadContext( rs )
          .getLoadingCollection( persister, collectionRowKey );


      if ( rowCollection != null ) {
        rowCollection.readFrom( rs, persister, descriptor, owner );
      }


    }
    else if ( optionalKey != null ) {
      // we did not find a collection element in the result set, so we

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    CollectionPersister persister = getPersister( session );
    final PersistenceContext persistenceContext = session.getPersistenceContext();
    final EntityMode entityMode = persister.getOwnerEntityPersister().getEntityMode();


    // check if collection is currently being loaded
    PersistentCollection collection = persistenceContext.getLoadContexts().locateLoadingCollection( persister, key );
    
    if ( collection == null ) {
      
      // check if it is already completely loaded, but unowned
      collection = persistenceContext.useUnownedCollection( new CollectionKey(persister, key, entityMode) );
      
      if ( collection == null ) {
        // create a new collection wrapper, to be initialized later
        collection = instantiate( session, persister, key );
        collection.setOwner(owner);
  
        persistenceContext.addUninitializedCollection( persister, collection, key );
  
        // some collections are not lazy:
        if ( initializeImmediately() ) {
          session.initializeCollection( collection, false );
        }
        else if ( !persister.isLazy() ) {
          persistenceContext.addNonLazyCollection( collection );
        }
  
        if ( hasHolder() ) {
          session.getPersistenceContext().addCollectionHolder( collection );
        }
        
      }
      
    }
    
    collection.setOwner(owner);


    return collection.getValue();
  }

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    LOG.trace( "Scheduling collection removes/(re)creates/updates" );


    ActionQueue actionQueue = session.getActionQueue();
    for ( Map.Entry<PersistentCollection,CollectionEntry> me :
      IdentityMap.concurrentEntries( (Map<PersistentCollection,CollectionEntry>) persistenceContext.getCollectionEntries() )) {
      PersistentCollection coll = me.getKey();
      CollectionEntry ce = me.getValue();


      if ( ce.isDorecreate() ) {
        session.getInterceptor().onCollectionRecreate( coll, ce.getCurrentKey() );
        actionQueue.addAction(

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    persistenceContext.getBatchFetchQueue()
        .clearSubselects(); //the database has changed now, so the subselect results need to be invalidated


    for ( Map.Entry<PersistentCollection, CollectionEntry> me : IdentityMap.concurrentEntries( persistenceContext.getCollectionEntries() ) ) {
      CollectionEntry collectionEntry = me.getValue();
      PersistentCollection persistentCollection = me.getKey();
      collectionEntry.postFlush(persistentCollection);
      if ( collectionEntry.getLoadedPersister() == null ) {
        //if the collection is dereferenced, remove from the session cache
        //iter.remove(); //does not work, since the entrySet is not backed by the set
        persistenceContext.getCollectionEntries()

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          //    with the current Session
          //throw new AssertionFailure("bug loading unowned collection");
        }
      }


      PersistentCollection rowCollection = persistenceContext.getLoadContexts()
          .getCollectionLoadContext( rs )
          .getLoadingCollection( persister, collectionRowKey );


      if ( rowCollection != null ) {
        rowCollection.readFrom( rs, persister, descriptor, owner );
      }


    }
    else if ( optionalKey != null ) {
      // we did not find a collection element in the result set, so we

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        if (LOG.isTraceEnabled()) LOG.trace("Starting attempt to find loading collection ["
                                            + MessageHelper.collectionInfoString(persister.getRole(), key) + "]");
    final LoadingCollectionEntry loadingCollectionEntry = loadContexts.locateLoadingCollectionEntry( collectionKey );
    if ( loadingCollectionEntry == null ) {
      // look for existing collection as part of the persistence context
      PersistentCollection collection = loadContexts.getPersistenceContext().getCollection( collectionKey );
      if ( collection != null ) {
        if ( collection.wasInitialized() ) {
                    LOG.trace("Collection already initialized; ignoring");
          return null; // ignore this row of results! Note the early exit
                }
                LOG.trace("Collection not yet initialized; initializing");
      }
      else {
        Object owner = loadContexts.getPersistenceContext().getCollectionOwner( key, persister );
        final boolean newlySavedEntity = owner != null
            && loadContexts.getPersistenceContext().getEntry( owner ).getStatus() != Status.LOADING
            && em != EntityMode.DOM4J;
        if ( newlySavedEntity ) {
          // important, to account for newly saved entities in query
          // todo : some kind of check for new status...
                    LOG.trace("Owning entity already loaded; ignoring");
          return null;
        }
                // create one
                LOG.trace("Instantiating new collection [key=" + key + ", rs=" + resultSet + "]");
                collection = persister.getCollectionType().instantiate(loadContexts.getPersistenceContext().getSession(),
                                                                       persister,
                                                                       key);
      }
      collection.beforeInitialize( persister, -1 );
      collection.beginRead();
      localLoadingCollectionKeys.add( collectionKey );
      loadContexts.registerLoadingCollectionXRef( collectionKey, new LoadingCollectionEntry( resultSet, persister, key, collection ) );
      return collection;
    }
        if (loadingCollectionEntry.getResultSet() == resultSet) {

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   * @param key The key of the collection's entry.
   */
  private void addCollection(PersistentCollection coll, CollectionEntry entry, Serializable key) {
    collectionEntries.put( coll, entry );
    final CollectionKey collectionKey = new CollectionKey( entry.getLoadedPersister(), key );
    final PersistentCollection old = collectionsByKey.put( collectionKey, coll );
    if ( old != null ) {
      if ( old == coll ) {
        throw new AssertionFailure( "bug adding collection twice" );
      }
      // or should it actually throw an exception?
      old.unsetSession( session );
      collectionEntries.remove( old );
      // watch out for a case where old is still referenced
      // somewhere in the object graph! (which is a user error)
    }
  }

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    return getCollectionEntry( coll ).getSnapshot();
  }


  @Override
  public CollectionEntry getCollectionEntryOrNull(Object collection) {
    PersistentCollection coll;
    if ( collection instanceof PersistentCollection ) {
      coll = (PersistentCollection) collection;
      //if (collection==null) throw new TransientObjectException("Collection was not yet persistent");
    }
    else {
      coll = getCollectionHolder( collection );
      if ( coll == null ) {
        //it might be an unwrapped collection reference!
        //try to find a wrapper (slowish)
        final Iterator<PersistentCollection> wrappers = collectionEntries.keyIterator();
        while ( wrappers.hasNext() ) {
          final PersistentCollection pc = wrappers.next();
          if ( pc.isWrapper( collection ) ) {
            coll = pc;
            break;
          }
        }
      }

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org.hibernate.action.internal.CollectionRecreateAction

org.hibernate.action.internal.CollectionRemoveAction

org.hibernate.action.internal.CollectionUpdateAction

org.hibernate.action.internal.QueuedOperationCollectionAction

org.hibernate.engine.internal.StatefulPersistenceContext

org.hibernate.engine.loading.internal.CollectionLoadContext

org.hibernate.engine.spi.BatchFetchQueue

org.hibernate.event.internal.AbstractFlushingEventListener

org.hibernate.event.internal.DefaultInitializeCollectionEventListener

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