BeanMap.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.Map;
import java.util.Set;

/**
 * This class wraps an existing map, and causes {@link PropertyChangeEvent}
 * events to be fired whenever it changes.
 * <p>
 * Adding objects to the map will result in events where the before value is
 * null and the after value is the key being added.
 * <p>
 * Removing them will result in events where the before value is they key 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 BeanMap#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 BeanMap extends WeakPropertyChangeSupport implements Map {

	private static final long serialVersionUID = 1L;

	private final Map delegate;

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

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

	/**
	 * Construct a new instance that wraps the delegate map and produces
	 * {@link PropertyChangeEvent} events whenever the delegate map changes.
	 * <p>
	 * As the delegate is a {@link BeanMap} instance, it doesn't wrap the map
	 * 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 map.
	 */
	public BeanMap(final BeanMap delegate) {
		this(delegate.delegate);
		final PropertyChangeListener[] listeners = delegate
				.getPropertyChangeListeners();
		for (int i = 0; i < listeners.length; i++)
			this.addPropertyChangeListener(listeners[i]);
	}

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

	public boolean containsKey(final Object key) {
		return this.delegate.containsKey(key);
	}

	public boolean containsValue(final Object value) {
		return this.delegate.containsValue(value);
	}

	private final PropertyChangeListener entrySetListener = new PropertyChangeListener() {
		public void propertyChange(final PropertyChangeEvent evt) {
			final Map.Entry oldValue = (Map.Entry) evt.getOldValue();
			final Map.Entry newValue = (Map.Entry) evt.getNewValue();
			BeanMap.this.firePropertyChange(BeanMap.propertyName,
					oldValue == null ? null : oldValue.getKey(),
					newValue == null ? null : newValue.getKey());
		}
	};
	
	public Set entrySet() {
		// Wrap the entry set in a BeanCollection.
		final BeanSet beanSet = new BeanSet(this.delegate.entrySet());
		// Add a PropertyChangeListener to the BeanSet
		// which fires events as if they came from us.
		beanSet.addPropertyChangeListener(this.entrySetListener);
		// Return the wrapped entry set.
		return beanSet;
	}

	public Object get(final Object key) {
		return this.delegate.get(key);
	}

	public boolean isEmpty() {
		return this.delegate.isEmpty();
	}

	private final PropertyChangeListener keySetListener = new PropertyChangeListener() {
		public void propertyChange(final PropertyChangeEvent evt) {
			BeanMap.this.firePropertyChange(BeanMap.propertyName, evt
					.getOldValue(), evt.getNewValue());
		}
	};
	
	public Set keySet() {
		// Wrap the entry set in a BeanCollection.
		final BeanSet beanSet = new BeanSet(this.delegate.keySet());
		// Add a PropertyChangeListener to the BeanSet
		// which fires events as if they came from us.
		beanSet.addPropertyChangeListener(this.keySetListener);
		// Return the wrapped entry set.
		return beanSet;
	}

	public Object put(final Object arg0, final Object arg1) {
		final boolean already = this.delegate.containsKey(arg0);
		final Object result = this.delegate.put(arg0, arg1);
		this.firePropertyChange(BeanMap.propertyName, already ? arg0 : null,
				arg0);
		return result;
	}

	public void putAll(final Map arg0) {
		this.delegate.putAll(arg0);
		this.firePropertyChange(BeanMap.propertyName, null, null);
	}

	public Object remove(final Object key) {
		final Object result = this.delegate.remove(key);
		this.firePropertyChange(BeanMap.propertyName, key, null);
		return result;
	}

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

	public Collection values() {
		return this.delegate.values();
	}

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

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

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

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

}