collectiontype.java

介绍了hibernate的入门有一些基本常用的事例

	 */
	public abstract PersistentCollection wrap(SessionImplementor session, Object collection);

	/**
	 * Note: return true because this type is castable to <tt>AssociationType</tt>. Not because
	 * all collections are associations.
	 */
	public boolean isAssociationType() {
		return true;
	}

	public ForeignKeyDirection getForeignKeyDirection() {
		return ForeignKeyDirection.FOREIGN_KEY_TO_PARENT;
	}

	/**
	 * Get the key value from the owning entity instance, usually the identifier, but might be some
	 * other unique key, in the case of property-ref
	 */
	public Serializable getKeyOfOwner(Object owner, SessionImplementor session) {
		
		EntityEntry e = session.getPersistenceContext().getEntry( owner );
		if ( e == null ) return null; // This just handles a particular case of component
									  // projection, perhaps get rid of it and throw an exception
		
		if ( foreignKeyPropertyName == null ) {
			return e.getId();
		}
		else {
			// TODO: at the point where we are resolving collection references, we don't
			// know if the uk value has been resolved (depends if it was earlier or
			// later in the mapping document) - now, we could try and use e.getStatus()
			// to decide to semiResolve(), trouble is that initializeEntity() reuses
			// the same array for resolved and hydrated values
			Object id = e.getLoadedValue( foreignKeyPropertyName );

			// NOTE VERY HACKISH WORKAROUND!!
			Type keyType = getPersister( session ).getKeyType();
			if ( !keyType.getReturnedClass().isInstance( id ) ) {
				id = (Serializable) keyType.semiResolve(
					e.getLoadedValue( foreignKeyPropertyName ),
					session,
					owner );
			}

			return (Serializable) id;
		}
	}

	public Object hydrate(ResultSet rs, String[] name, SessionImplementor session, Object owner) {
		// can't just return null here, since that would
		// cause an owning component to become null
		return NOT_NULL_COLLECTION;
	}

	public Object resolve(Object value, SessionImplementor session, Object owner)
			throws HibernateException {
		
		return resolveKey( getKeyOfOwner( owner, session ), session, owner );
	}
	
	private Object resolveKey(Serializable key, SessionImplementor session, Object owner) {
		// if (key==null) throw new AssertionFailure("owner identifier unknown when re-assembling
		// collection reference");
		return key == null ? null : // TODO: can this case really occur??
			getCollection( key, session, owner );
	}

	public Object semiResolve(Object value, SessionImplementor session, Object owner)
			throws HibernateException {
		throw new UnsupportedOperationException(
			"collection mappings may not form part of a property-ref" );
	}

	public boolean isArrayType() {
		return false;
	}

	public boolean useLHSPrimaryKey() {
		return foreignKeyPropertyName == null;
	}

	public String getRHSUniqueKeyPropertyName() {
		return null;
	}

	public Joinable getAssociatedJoinable(SessionFactoryImplementor factory)
			throws MappingException {
		return (Joinable) factory.getCollectionPersister( role );
	}

	public boolean isModified(Object old, Object current, SessionImplementor session) throws HibernateException {
		return false;
	}

	public String getAssociatedEntityName(SessionFactoryImplementor factory)
			throws MappingException {
		try {
			
			QueryableCollection collectionPersister = (QueryableCollection) factory
				.getCollectionPersister( role );
			
			if ( !collectionPersister.getElementType().isEntityType() ) {
				throw new MappingException( "collection was not an association: "
					+ collectionPersister.getRole() );
			}
			
			return collectionPersister.getElementPersister().getEntityName();
			
		}
		catch (ClassCastException cce) {
			throw new MappingException( "collection role is not queryable " + role );
		}
	}

	/**
	 * Replace the elements of a collection with the elements of another collection
	 */
	public Object replaceElements(Object original, Object target, Object owner, Map copyCache,
			SessionImplementor session) throws HibernateException {

		// TODO: does not work for EntityMode.DOM4J yet!

		java.util.Collection result = (java.util.Collection) target;

		result.clear();

		// copy elements into newly empty target collection
		Type elemType = getElementType( session.getFactory() );
		Iterator iter = ( (java.util.Collection) original ).iterator();
		while ( iter.hasNext() ) {
			result.add( elemType.replace( iter.next(), null, session, owner, copyCache ) );
		}

		return result;

	}

	/**
	 * Instantiate an empty instance of the "underlying" collection (not a wrapper)
	 */
	public abstract Object instantiate(Object original);

	public Object replace(final Object original, final Object target,
			final SessionImplementor session, final Object owner, final Map copyCache)
			throws HibernateException {

		if ( original == null ) return null;
		if ( !Hibernate.isInitialized( original ) ) return target;
		if ( original == target ) return target; // is this really a Good Thing?

		Object result = target == null ? instantiate( original ) : target;
		return replaceElements( original, result, owner, copyCache, session );

	}

	/**
	 * Get the Hibernate type of the collection elements
	 */
	public final Type getElementType(SessionFactoryImplementor factory) throws MappingException {
		return factory.getCollectionPersister( getRole() ).getElementType();
	}

	public String toString() {
		return getClass().getName() + '(' + getRole() + ')';
	}

	public String getOnCondition(String alias, SessionFactoryImplementor factory, Map enabledFilters)
			throws MappingException {
		return getAssociatedJoinable( factory ).filterFragment( alias, enabledFilters );
	}

	/**
	 * instantiate a collection wrapper (called when loading an object)
	 */
	public Object getCollection(Serializable key, SessionImplementor session, Object owner)
			throws HibernateException {

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

		if (entityMode==EntityMode.DOM4J && !isEmbeddedInXML) {
			return UNFETCHED_COLLECTION;
		}
		
		// check if collection is currently being loaded
		PersistentCollection collection = persistenceContext
			.getCollectionLoadContext()
			.getLoadingCollection( persister, key, entityMode );
		
		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( collection, persister, key, entityMode );
	
				// some collections are not lazy:
				if ( initializeImmediately( entityMode ) ) {
					session.initializeCollection( collection, false );
				}
				else if ( !persister.isLazy() ) {
					persistenceContext.addNonLazyCollection( collection );
				}
	
				if ( hasHolder( entityMode ) ) {
					session.getPersistenceContext().addCollectionHolder( collection );
				}
				
			}
			
		}
		
		collection.setOwner(owner);

		return collection.getValue();
	}

	public boolean hasHolder(EntityMode entityMode) {
		return entityMode == EntityMode.DOM4J;
	}

	protected boolean initializeImmediately(EntityMode entityMode) {
		return entityMode == EntityMode.DOM4J;
	}

	public String getLHSPropertyName() {
		return foreignKeyPropertyName;
	}

	public boolean isXMLElement() {
		return true;
	}

	public Object fromXMLNode(Node xml, Mapping factory) throws HibernateException {
		return xml;
	}

	public void setToXMLNode(Node node, Object value, SessionFactoryImplementor factory) 
	throws HibernateException {
		if ( !isEmbeddedInXML ) {
			node.detach();
		}
		else {
			replaceNode( node, (Element) value );
		}
	}
	
	public boolean isAlwaysDirtyChecked() {
		return true; 
		// because we sometimes need to incremement version number of owner
		// and also because of how assemble/disassemble is implemented for uks
	}
}