Examples of org.hibernate.collection.PersistentCollection

org.hibernate.collection.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


    if (collection!=null) {


      SessionImplementor session = getSession();


      final PersistentCollection persistentCollection;
      if ( type.isArrayType() ) {
         persistentCollection = session.getPersistenceContext().getCollectionHolder(collection);
        // if no array holder we found an unwrappered array (this can't occur,
        // because we now always call wrap() before getting to here)
        // return (ah==null) ? true : searchForDirtyCollections(ah, type);
      }
      else {
        // if not wrappered yet, its dirty (this can't occur, because
        // we now always call wrap() before getting to here)
        // return ( ! (obj instanceof PersistentCollection) ) ?
        //true : searchForDirtyCollections( (PersistentCollection) obj, type );
        persistentCollection = (PersistentCollection) collection;
      }


      if ( persistentCollection.isDirty() ) { //we need to check even if it was not initialized, because of delayed adds!
        dirty=true;
        return null; //NOTE: EARLY EXIT!
      }
    }

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    }
    else {
      return; //EARLY EXIT!
    }


    PersistentCollection collection = (PersistentCollection) pc;
    if ( collection.unsetSession( getSession() ) ) evictCollection(collection);
  }

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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 );
    CollectionKey collectionKey = new CollectionKey( entry.getLoadedPersister(), key, session.getEntityMode() );
    PersistentCollection old = ( PersistentCollection ) 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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   * Get the collection entry for a collection passed to filter,
   * which might be a collection wrapper, an array, or an unwrapped
   * collection. Return null if there is no entry.
   */
  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)
        Iterator wrappers = IdentityMap.keyIterator(collectionEntries);
        while ( wrappers.hasNext() ) {
          PersistentCollection pc = (PersistentCollection) wrappers.next();
          if ( pc.isWrapper(collection) ) {
            coll = pc;
            break;
          }
        }
      }

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      count = ois.readInt();
      log.trace( "staring deserialization of [" + count + "] collectionEntries entries" );
      rtn.collectionEntries = IdentityMap.instantiateSequenced( count < INIT_COLL_SIZE ? INIT_COLL_SIZE : count );
      for ( int i = 0; i < count; i++ ) {
        final PersistentCollection pc = ( PersistentCollection ) ois.readObject();
        final CollectionEntry ce = CollectionEntry.deserialize( ois, session );
        pc.setCurrentSession( session );
        rtn.collectionEntries.put( pc, ce );
      }


      count = ois.readInt();
      log.trace( "staring deserialization of [" + count + "] arrayHolders entries" );

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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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   * @param key The key of the collection's entry.
   */
  private void addCollection(PersistentCollection coll, CollectionEntry entry, Serializable key) {
    collectionEntries.put( coll, entry );
    CollectionKey collectionKey = new CollectionKey( entry.getLoadedPersister(), key, session.getEntityMode() );
    PersistentCollection old = ( PersistentCollection ) 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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   * Get the collection entry for a collection passed to filter,
   * which might be a collection wrapper, an array, or an unwrapped
   * collection. Return null if there is no entry.
   */
  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)
        Iterator wrappers = IdentityMap.keyIterator(collectionEntries);
        while ( wrappers.hasNext() ) {
          PersistentCollection pc = (PersistentCollection) wrappers.next();
          if ( pc.isWrapper(collection) ) {
            coll = pc;
            break;
          }
        }
      }

View Full Code Here


      count = ois.readInt();
      log.trace( "staring deserialization of [" + count + "] collectionEntries entries" );
      rtn.collectionEntries = IdentityMap.instantiateSequenced( count < INIT_COLL_SIZE ? INIT_COLL_SIZE : count );
      for ( int i = 0; i < count; i++ ) {
        final PersistentCollection pc = ( PersistentCollection ) ois.readObject();
        final CollectionEntry ce = CollectionEntry.deserialize( ois, session );
        pc.setCurrentSession( session );
        rtn.collectionEntries.put( pc, ce );
      }


      count = ois.readInt();
      log.trace( "staring deserialization of [" + count + "] arrayHolders entries" );

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    if (collection==CollectionType.UNFETCHED_COLLECTION) {
      return null;
    }


    if (collection!=null) {
      final PersistentCollection coll;
      if ( type.hasHolder( getSession().getEntityMode() ) ) {
        coll = getSession().getPersistenceContext().getCollectionHolder(collection);
      }
      else {
        coll = (PersistentCollection) collection;

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