identifierbag.java

用Java实现的23个常用设计模式源代码

package net.sf.hibernate.collection;

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.JDBCException;
import net.sf.hibernate.engine.SessionImplementor;
import net.sf.hibernate.type.Type;

/**
 * An <tt>IdentifierBag</tt> implements "bag" semantics more efficiently than
 * a regular <tt>Bag</tt> by adding a synthetic identifier column to the
 * table. This identifier is unique for all rows in the table, allowing very
 * efficient updates and deletes. The value of the identifier is never exposed
 * to the application.<br>
 * <br>
 * <tt>IdentifierBag</tt>s may not be used for a many-to-one association.
 * Furthermore, there is no reason to use <tt>inverse="true"</tt>.
 * 
 * @author Gavin King
 */
public class IdentifierBag extends ODMGCollection implements java.util.List {
	
	private java.util.List values;
	private java.util.Map identifiers; //element -> id
	
	public IdentifierBag(SessionImplementor session) {
		super(session);
	}

	public IdentifierBag() {} //needed for SOAP libraries, etc

	public IdentifierBag(SessionImplementor session, java.util.Collection coll) {
		super(session);
		if (coll instanceof java.util.List) {
			values = (java.util.List) coll;
		}
		else {
			values = new ArrayList();
			Iterator iter = coll.iterator();
			while ( iter.hasNext() ) {
				values.add( iter.next() );
			}
		}
		setInitialized(true);
		setDirectlyAccessible(true);
		identifiers = new HashMap();
	}
	
	public IdentifierBag(SessionImplementor session, CollectionPersister persister, Serializable disassembled, Object owner)
	throws HibernateException {
		super(session);
		beforeInitialize(persister);
		Serializable[] array = (Serializable[]) disassembled;
		for (int i=0; i<array.length; i+=2 ) {
			Object value = persister.getElementType().assemble( array[i+1], session, owner );
			identifiers.put(
				value,
				persister.getIdentifierType().assemble( array[i], session, owner )
			);
			values.add(value);
		}
		setInitialized(true);
	}
	
	public boolean isWrapper(Object collection) {
		return values==collection;
	}
	public boolean add(Object o) {
		write();
		values.add(o);
		return true;
	}
	
	public void clear() {
		write();
		values.clear();
		identifiers.clear();
	}

	public boolean contains(Object o) {
		read();
		return values.contains(o);
	}

	public boolean containsAll(Collection c) {
		read();
		return values.containsAll(c);
	}

	public boolean isEmpty() {
		read();
		return values.isEmpty();
	}

	public Iterator iterator() {
		read();
		return values.iterator();
	}

	public boolean remove(Object o) {
		write();
		return values.remove(o);
	}

	public boolean removeAll(Collection c) {
		if ( c.size()>0 ) {
			write();
			return values.removeAll(c);
		}
		else {
			return false;
		}
	}

	public boolean retainAll(Collection c) {
		write();
		return values.retainAll(c);
	}

	public int size() {
		read();
		return values.size();
	}

	public Object[] toArray() {
		read();
		return values.toArray();
	}

	public Object[] toArray(Object[] a) {
		read();
		return values.toArray();
	}

	public void beforeInitialize(CollectionPersister persister) {
		identifiers = new HashMap();
		values = new ArrayList();
	}

	public Serializable disassemble(CollectionPersister persister)
		throws HibernateException {
		
		Serializable[] result = new Serializable[ values.size() * 2 ];
		Iterator iter = values.iterator();
		int i=0;
		while ( iter.hasNext() ) {
			Object value = iter.next();
			result[i++] = persister.getIdentifierType().disassemble( identifiers.get(value), getSession() );
			result[i++] = persister.getElementType().disassemble( value, getSession() );
		}
		return result;
	}

	public boolean empty() {
		return values.isEmpty();
	}

	public Iterator entries() {
		return values.iterator();
	}

	public boolean entryExists(Object entry, int i) {
		return entry!=null;
	}

	public boolean equalsSnapshot(Type elementType) throws HibernateException {
		java.util.Map snap = (java.util.Map) getSnapshot();
		if ( snap.size()!= values.size() ) return false;
		Iterator iter = values.iterator();
		int i=0;
		while ( iter.hasNext() ) {
			Object value = iter.next();
			Object id = identifiers.get( new Integer(i++) );
			if (id==null) return false;
			Object old = snap.get(id);
			if ( elementType.isDirty( old, value, getSession() ) ) return false;
		}
		return true;
	}

	public Iterator getDeletes(Type elemType) throws HibernateException {
		java.util.Map snap = (java.util.Map) getSnapshot();
		java.util.List deletes = new ArrayList( snap.keySet() );
		Iterator iter = values.iterator();
		int i=0;
		while ( iter.hasNext() ) {
			if ( iter.next()!=null ) deletes.remove( identifiers.get( new Integer(i++) ) );
		}
		return deletes.iterator();
	}

	public Object getIndex(Object entry, int i) {
		throw new UnsupportedOperationException("Bags don't have indexes");
	}

	public boolean needsInserting(Object entry, int i, Type elemType)
		throws HibernateException {
		
		java.util.Map snap = (java.util.Map) getSnapshot();
		Object id = identifiers.get( new Integer(i) );
		return entry!=null && ( id==null || snap.get(id)==null );
	}

	public boolean needsUpdating(Object entry, int i, Type elemType) throws HibernateException {
		
		if (entry==null) return false;
		java.util.Map snap = (java.util.Map) getSnapshot();
		Object id = identifiers.get( new Integer(i) );
		if (id==null) return false;
		Object old = snap.get(id);
		return old!=null && elemType.isDirty( old, entry, getSession() );
	}


	public Object readFrom(
		ResultSet rs,
		CollectionPersister persister,
		Object owner)
		throws HibernateException, SQLException {
		
		Object element = persister.readElement( rs, owner, getSession() );
		Object old = identifiers.put( 
			new Integer( values.size() ), 
			persister.readIdentifier( rs, getSession() )
		);
		if ( old==null ) values.add(element); //maintain correct duplication if loaded in a cartesian product
		return element;
	}

	protected Serializable snapshot(CollectionPersister persister)
		throws HibernateException {
			
		HashMap map = new HashMap( values.size() );
		Iterator iter = values.iterator();
		int i=0;
		while ( iter.hasNext() ) {
			Object value = iter.next();
			map.put( 
				identifiers.get( new Integer(i++) ), 
				persister.getElementType().deepCopy(value) 
			);
		}
		return map;
	}
	
	public Collection getOrphans(Serializable snapshot) throws HibernateException {
		java.util.Map sn = (java.util.Map) snapshot;
		ArrayList result = new ArrayList( sn.values() );
		PersistentCollection.identityRemoveAll( result, values, getSession() );
		return result;
	}
	
	public void preInsert(CollectionPersister persister) throws HibernateException {
		try {
			Iterator iter = entries();
			int i=0;
			while ( iter.hasNext() ) {
				Object entry = iter.next();
				Integer loc = new Integer(i++);
				if ( !identifiers.containsKey(loc) ) { //TODO: native ids
					Serializable id = persister.getIdentifierGenerator().generate( getSession(), entry );
					identifiers.put(loc, id);
				}
			}
		}
		catch (SQLException sqle) {
			throw new JDBCException("could not generate idbag row id", sqle);
		}
	}
	
	public void writeTo(
		PreparedStatement st,
		CollectionPersister persister,
		Object entry,
		int i,
		boolean writeOrder)
		throws HibernateException, SQLException {
		
		persister.writeElement( st, entry, writeOrder, getSession() );
		//TODO: if not using identity columns:
		persister.writeIdentifier( st, identifiers.get( new Integer(i) ), writeOrder, getSession() );

	}

	public void add(int index, Object element) {
		write();
		values.add(index, element);
	}

	public boolean addAll(int index, Collection c) {
		if ( c.size()>0 ) {
			write();
			return values.addAll(index, c);
		}
		else {
			return false;
		}
	}

	public Object get(int index) {
		read();
		return values.get(index);
	}

	public int indexOf(Object o) {
		read();
		return values.indexOf(o);
	}

	public int lastIndexOf(Object o) {
		read();
		return values.lastIndexOf(o);
	}

	public ListIterator listIterator() {
		read();
		return values.listIterator();
	}

	public ListIterator listIterator(int index) {
		read();
		return values.listIterator(index);
	}

	public Object remove(int index) {
		write();
		return values.remove(index);
	}

	public Object set(int index, Object element) {
		write();
		return values.set(index, element);
	}

	public List subList(int fromIndex, int toIndex) {
		read();
		return values.subList(fromIndex, toIndex);
	}
	
	public boolean addAll(Collection c) {
		if ( c.size()> 0 ) {
			write();
			return values.addAll(c);
		}
		else {
			return false;
		}
	}

	public void afterRowInsert(
		CollectionPersister persister,
		Object entry,
		int i)
		throws HibernateException {
		//TODO: if we are using identity columns, fetch the identifier
	}

}