abstractpersistentcollection.java

一个Java持久层类库

//$Id: AbstractPersistentCollection.java 11302 2007-03-19 20:44:11Z [e-mail] $
package org.hibernate.collection;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

import org.hibernate.AssertionFailure;
import org.hibernate.HibernateException;
import org.hibernate.LazyInitializationException;
import org.hibernate.engine.CollectionEntry;
import org.hibernate.engine.ForeignKeys;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.engine.TypedValue;
import org.hibernate.persister.collection.CollectionPersister;
import org.hibernate.pretty.MessageHelper;
import org.hibernate.type.Type;
import org.hibernate.util.CollectionHelper;
import org.hibernate.util.EmptyIterator;
import org.hibernate.util.MarkerObject;

/**
 * Base class implementing <tt>PersistentCollection</tt>
 * @see PersistentCollection
 * @author Gavin King
 */
public abstract class AbstractPersistentCollection 
	implements Serializable, PersistentCollection {

	private transient SessionImplementor session;
	private boolean initialized;
	private transient List operationQueue;
	private transient boolean directlyAccessible;
	private transient boolean initializing;
	private Object owner;
	private int cachedSize = -1;
	
	private String role;
	private Serializable key;
	// collections detect changes made via their public interface and mark
	// themselves as dirty as a performance optimization
	private boolean dirty;
	private Serializable storedSnapshot;

	public final String getRole() {
		return role;
	}
	
	public final Serializable getKey() {
		return key;
	}
	
	public final boolean isUnreferenced() {
		return role==null;
	}
	
	public final boolean isDirty() {
		return dirty;
	}
	
	public final void clearDirty() {
		dirty = false;
	}
	
	public final void dirty() {
		dirty = true;
	}
	
	public final Serializable getStoredSnapshot() {
		return storedSnapshot;
	}
	
	//Careful: these methods do not initialize the collection.
	/**
	 * Is the initialized collection empty?
	 */
	public abstract boolean empty();
	/**
	 * Called by any read-only method of the collection interface
	 */
	protected final void read() {
		initialize(false);
	}
	/**
	 * Called by the <tt>size()</tt> method
	 */
	protected boolean readSize() {
		if (!initialized) {
			if ( cachedSize!=-1 && !hasQueuedOperations() ) {
				return true;
			}
			else {
				throwLazyInitializationExceptionIfNotConnected();
				CollectionEntry entry = session.getPersistenceContext().getCollectionEntry(this);
				CollectionPersister persister = entry.getLoadedPersister();
				if ( persister.isExtraLazy() ) {
					if ( hasQueuedOperations() ) {
						session.flush();
					}
					cachedSize = persister.getSize( entry.getLoadedKey(), session );
					return true;
				}
			}
		}
		read();
		return false;
	}
	
	protected Boolean readIndexExistence(Object index) {
		if (!initialized) {
			throwLazyInitializationExceptionIfNotConnected();
			CollectionEntry entry = session.getPersistenceContext().getCollectionEntry(this);
			CollectionPersister persister = entry.getLoadedPersister();
			if ( persister.isExtraLazy() ) {
				if ( hasQueuedOperations() ) {
					session.flush();
				}
				return new Boolean( persister.indexExists( entry.getLoadedKey(), index, session ) );
			}
		}
		read();
		return null;
		
	}
	
	protected Boolean readElementExistence(Object element) {
		if (!initialized) {
			throwLazyInitializationExceptionIfNotConnected();
			CollectionEntry entry = session.getPersistenceContext().getCollectionEntry(this);
			CollectionPersister persister = entry.getLoadedPersister();
			if ( persister.isExtraLazy() ) {
				if ( hasQueuedOperations() ) {
					session.flush();
				}
				return new Boolean( persister.elementExists( entry.getLoadedKey(), element, session ) );
			}
		}
		read();
		return null;
		
	}
	
	protected static final Object UNKNOWN = new MarkerObject("UNKNOWN");
	
	protected Object readElementByIndex(Object index) {
		if (!initialized) {
			throwLazyInitializationExceptionIfNotConnected();
			CollectionEntry entry = session.getPersistenceContext().getCollectionEntry(this);
			CollectionPersister persister = entry.getLoadedPersister();
			if ( persister.isExtraLazy() ) {
				if ( hasQueuedOperations() ) {
					session.flush();
				}
				return persister.getElementByIndex( entry.getLoadedKey(), index, session, owner );
			}
		}
		read();
		return UNKNOWN;
		
	}
	
	protected int getCachedSize() {
		return cachedSize;
	}
	
	/**
	 * Is the collection currently connected to an open session?
	 */
	private final boolean isConnectedToSession() {
		return session!=null && 
				session.isOpen() &&
				session.getPersistenceContext().containsCollection(this);
	}

	/**
	 * Called by any writer method of the collection interface
	 */
	protected final void write() {
		initialize(true);
		dirty();
	}
	/**
	 * Is this collection in a state that would allow us to
	 * "queue" operations?
	 */
	protected boolean isOperationQueueEnabled() {
		return !initialized &&
				isConnectedToSession() &&
				isInverseCollection();
	}
	/**
	 * Is this collection in a state that would allow us to
	 * "queue" puts? This is a special case, because of orphan
	 * delete.
	 */
	protected boolean isPutQueueEnabled() {
		return !initialized &&
				isConnectedToSession() &&
				isInverseOneToManyOrNoOrphanDelete();
	}
	/**
	 * Is this collection in a state that would allow us to
	 * "queue" clear? This is a special case, because of orphan
	 * delete.
	 */
	protected boolean isClearQueueEnabled() {
		return !initialized &&
				isConnectedToSession() &&
				isInverseCollectionNoOrphanDelete();
	}

	/**
	 * Is this the "inverse" end of a bidirectional association?
	 */
	private boolean isInverseCollection() {
		CollectionEntry ce = session.getPersistenceContext().getCollectionEntry(this);
		return ce != null && ce.getLoadedPersister().isInverse();
	}

	/**
	 * Is this the "inverse" end of a bidirectional association with
	 * no orphan delete enabled?
	 */
	private boolean isInverseCollectionNoOrphanDelete() {
		CollectionEntry ce = session.getPersistenceContext().getCollectionEntry(this);
		return ce != null && 
				ce.getLoadedPersister().isInverse() &&
				!ce.getLoadedPersister().hasOrphanDelete();
	}

	/**
	 * Is this the "inverse" end of a bidirectional one-to-many, or 
	 * of a collection with no orphan delete?
	 */
	private boolean isInverseOneToManyOrNoOrphanDelete() {
		CollectionEntry ce = session.getPersistenceContext().getCollectionEntry(this);
		return ce != null && ce.getLoadedPersister().isInverse() && (
				ce.getLoadedPersister().isOneToMany() || 
				!ce.getLoadedPersister().hasOrphanDelete() 
			);
	}

	/**
	 * Queue an addition
	 */
	protected final void queueOperation(Object element) {
		if (operationQueue==null) operationQueue = new ArrayList(10);
		operationQueue.add(element);
		dirty = true; //needed so that we remove this collection from the second-level cache
	}

	/**
	 * After reading all existing elements from the database,
	 * add the queued elements to the underlying collection.
	 */
	protected final void performQueuedOperations() {
		for ( int i=0; i<operationQueue.size(); i++ ) {
			( (DelayedOperation) operationQueue.get(i) ).operate();
		}
	}

	/**
	 * After flushing, re-init snapshot state.
	 */
	public void setSnapshot(Serializable key, String role, Serializable snapshot) {
		this.key = key;
		this.role = role;
		this.storedSnapshot = snapshot;
	}

	/**
	 * After flushing, clear any "queued" additions, since the
	 * database state is now synchronized with the memory state.
	 */
	public void postAction() {
		operationQueue=null;
		cachedSize = -1;
		clearDirty();
	}
	
	/**
	 * Not called by Hibernate, but used by non-JDK serialization,
	 * eg. SOAP libraries.
	 */
	public AbstractPersistentCollection() {}

	protected AbstractPersistentCollection(SessionImplementor session) {
		this.session = session;
	}

	/**
	 * return the user-visible collection (or array) instance
	 */
	public Object getValue() {
		return this;
	}

	/**
	 * Called just before reading any rows from the JDBC result set
	 */
	public void beginRead() {
		// override on some subclasses
		initializing = true;
	}

	/**
	 * Called after reading all rows from the JDBC result set
	 */
	public boolean endRead() {
		//override on some subclasses
		return afterInitialize();
	}
	
	public boolean afterInitialize() {
		setInitialized();
		//do this bit after setting initialized to true or it will recurse
		if (operationQueue!=null) {
			performQueuedOperations();
			operationQueue=null;
			cachedSize = -1;
			return false;
		}
		else {
			return true;
		}
	}

	/**
	 * Initialize the collection, if possible, wrapping any exceptions
	 * in a runtime exception
	 * @param writing currently obsolete
	 * @throws LazyInitializationException if we cannot initialize
	 */
	protected final void initialize(boolean writing) {
		if (!initialized) {
			if (initializing) {
				throw new LazyInitializationException("illegal access to loading collection");
			}
			throwLazyInitializationExceptionIfNotConnected();
			session.initializeCollection(this, writing);
		}
	}
	
	private void throwLazyInitializationExceptionIfNotConnected() {
		if ( !isConnectedToSession() )  {
			throwLazyInitializationException("no session or session was closed");
		}
		if ( !session.isConnected() ) {
            throwLazyInitializationException("session is disconnected");
		}		
	}
	
	private void throwLazyInitializationException(String message) {
		throw new LazyInitializationException(
				"failed to lazily initialize a collection" + 
				( role==null ?  "" : " of role: " + role ) + 
				", " + message
			);
	}

	protected final void setInitialized() {
		this.initializing = false;
		this.initialized = true;
	}

	protected final void setDirectlyAccessible(boolean directlyAccessible) {
		this.directlyAccessible = directlyAccessible;
	}

	/**
	 * Could the application possibly have a direct reference to
	 * the underlying collection implementation?
	 */
	public boolean isDirectlyAccessible() {
		return directlyAccessible;
	}

	/**
	 * Disassociate this collection from the given session.
	 * @return true if this was currently associated with the given session
	 */
	public final boolean unsetSession(SessionImplementor currentSession) {
		if (currentSession==this.session) {
			this.session=null;
			return true;
		}
		else {
			return false;
		}
	}

	/**
	 * Associate the collection with the given session.
	 * @return false if the collection was already associated with the session
	 * @throws HibernateException if the collection was already associated
	 * with another open session
	 */
	public final boolean setCurrentSession(SessionImplementor session) throws HibernateException {
		if (session==this.session) {
			return false;
		}
		else {
			if ( isConnectedToSession() ) {
				CollectionEntry ce = session.getPersistenceContext().getCollectionEntry(this);
				if (ce==null) {
					throw new HibernateException(
							"Illegal attempt to associate a collection with two open sessions"
						);
				}
				else {
					throw new HibernateException(
							"Illegal attempt to associate a collection with two open sessions: " +
							MessageHelper.collectionInfoString( 
									ce.getLoadedPersister(), 
									ce.getLoadedKey(), 
									session.getFactory() 
								)
						);
				}
			}
			else {
				this.session = session;
				return true;
			}
		}
	}

	/**
	 * Do we need to completely recreate this collection when it changes?
	 */
	public boolean needsRecreate(CollectionPersister persister) {
		return false;
	}
	
	/**
	 * To be called internally by the session, forcing
	 * immediate initialization.
	 */
	public final void forceInitialization() throws HibernateException {
		if (!initialized) {
			if (initializing) {
				throw new AssertionFailure("force initialize loading collection");
			}
			if (session==null) {
				throw new HibernateException("collection is not associated with any session");
			}
			if ( !session.isConnected() ) {
				throw new HibernateException("disconnected session");
			}
			session.initializeCollection(this, false);
		}
	}


	/**
	 * Get the current snapshot from the session
	 */
	protected final Serializable getSnapshot() {
		return session.getPersistenceContext().getSnapshot(this);
	}

	/**
	 * Is this instance initialized?
	 */
	public final boolean wasInitialized() {
		return initialized;
	}