BeanCollection.java

/*
 Copyright (C) 2006 EBI
 
 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
 License as published by the Free Software Foundation; either
 version 2.1 of the License, or (at your option) any later version.
 
 This library is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the itmplied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 Lesser General Public License for more details.
 
 You should have received a copy of the GNU Lesser General Public
 License along with this library; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.biomart.common.utils;

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Collection;
import java.util.Iterator;

/**
 * This class wraps an existing collection, and causes
 * {@link PropertyChangeEvent} events to be fired whenever it changes.
 * <p>
 * Adding objects to the collection will result in events where the before value
 * is null and the after value is the value being added.
 * <p>
 * Removing them will result in events where the before value is they value
 * being removed and the after value is null.
 * <p>
 * Multiple add/remove events will have both before and after values of null.
 * <p>
 * All events will have a property of {@link BeanCollection#propertyName}.
 * 
 * @author Richard Holland <holland@ebi.ac.uk>
 * @version $Revision: 1.4 $, $Date: 2007-10-31 10:32:56 $, modified by 	
 * 			$Author: rh4 $
 * @since 0.7
 */
public class BeanCollection extends WeakPropertyChangeSupport implements Collection {

	private static final long serialVersionUID = 1L;

	/**
	 * This field is for use by subclasses which need to access the delegate
	 * directly.
	 */
	protected final Collection delegate;

	/**
	 * The property key used in events generated by this map.
	 */
	public static final String propertyName = "CollectionEntry";

	/**
	 * Construct a new instance that wraps the delegate collection and produces
	 * {@link PropertyChangeEvent} events whenever the delegate collection
	 * changes.
	 * 
	 * @param delegate
	 *            the delegate collection.
	 */
	public BeanCollection(final Collection delegate) {
		super(delegate);
		this.delegate = delegate;
	}

	/**
	 * Construct a new instance that wraps the delegate collection and produces
	 * {@link PropertyChangeEvent} events whenever the delegate collection
	 * changes.
	 * <p>
	 * As the delegate is a {@link BeanCollection} instance, it doesn't wrap the
	 * collection directly, instead it finds out the delegate's delegate and
	 * wraps that instead. It will also notify all listeners that are already
	 * listening to the delegate.
	 * 
	 * @param delegate
	 *            the delegate collection.
	 */
	public BeanCollection(final BeanCollection delegate) {
		this(delegate.delegate);
		final PropertyChangeListener[] listeners = delegate
				.getPropertyChangeListeners();
		for (int i = 0; i < listeners.length; i++)
			this.addPropertyChangeListener(listeners[i]);
	}

	public boolean add(final Object arg0) {
		final boolean result = this.delegate.add(arg0);
		if (result)
			this.firePropertyChange(BeanCollection.propertyName, null, arg0);
		return result;
	}

	public boolean addAll(final Collection arg0) {
		final boolean result = this.delegate.addAll(arg0);
		if (result)
			this.firePropertyChange(BeanCollection.propertyName, null, null);
		return result;
	}

	public void clear() {
		this.delegate.clear();
		this.firePropertyChange(BeanCollection.propertyName, null, null);
	}

	public boolean contains(final Object o) {
		return this.delegate.contains(o);
	}

	public boolean containsAll(final Collection arg0) {
		return this.delegate.containsAll(arg0);
	}

	public boolean isEmpty() {
		return this.delegate.isEmpty();
	}
	
	private final PropertyChangeListener iteratorListener = new PropertyChangeListener() {
		public void propertyChange(final PropertyChangeEvent evt) {
			BeanCollection.this.firePropertyChange(
					BeanCollection.propertyName, evt.getOldValue(), evt
							.getNewValue());
		}
	};

	public Iterator iterator() {
		// Wrap the entry set in a BeanIterator.
		final BeanIterator beanIterator = new BeanIterator(this.delegate
				.iterator());
		// Add a PropertyChangeListener to the BeanSet
		// which fires events as if they came from us.
		beanIterator.addPropertyChangeListener(this.iteratorListener);
		// Return the wrapped entry set.
		return beanIterator;
	}

	public boolean remove(final Object o) {
		final boolean result = this.delegate.remove(o);
		if (result)
			this.firePropertyChange(BeanCollection.propertyName, o, null);
		return result;
	}

	public boolean removeAll(final Collection arg0) {
		final boolean result = this.delegate.removeAll(arg0);
		if (result)
			this.firePropertyChange(BeanCollection.propertyName, null, null);
		return result;
	}

	public boolean retainAll(final Collection arg0) {
		final boolean result = this.delegate.retainAll(arg0);
		if (result)
			this.firePropertyChange(BeanCollection.propertyName, null, null);
		return result;
	}

	public int size() {
		return this.delegate.size();
	}

	public Object[] toArray() {
		return this.delegate.toArray();
	}

	public Object[] toArray(final Object[] arg0) {
		return this.delegate.toArray(arg0);
	}

	protected Object clone() throws CloneNotSupportedException {
		throw new CloneNotSupportedException();
	}

	public boolean equals(final Object obj) {
		if (obj == this)
			return true;
		else if (obj instanceof BeanCollection)
			return this.delegate.equals(((BeanCollection) obj).delegate);
		else if (obj instanceof Collection)
			return this.delegate.equals(obj);
		else
			return false;
	}

	public int hashCode() {
		return this.delegate.hashCode();
	}

	public String toString() {
		return this.delegate.toString();
	}
}