/* PropertyChangeListenerProxy.java -- adds a name to a property listener
   Copyright (C) 2002, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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02111-1307 USA.

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permission to link this library with independent modules to produce an
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package java.beans;

import java.util.EventListenerProxy;

/**
 * This class provides an extension to <code>PropertyChangeListener</code> -
 * associating a name with the listener. This can be used to filter the
 * changes that one is interested in.
 *
 * @author Eric Blake (ebb9@email.byu.edu)
 * @since 1.4
 * @status udpated to 1.4
 */
public class PropertyChangeListenerProxy extends EventListenerProxy
  implements PropertyChangeListener
{
  /**
   * The name of the property to listen for. Package visible for use by
   * PropertyChangeSupport.
   */
  final String propertyName;

  /**
   * Create a new proxy which filters property change events and only passes
   * changes to the named property on to the delegate. A null propertyName
   * or listener does not fail now, but may cause a NullPointerException down
   * the road.
   *
   * @param propertyName the property's name to filter on
   * @param listener the delegate listener
   */
  public PropertyChangeListenerProxy(String propertyName,
                                     PropertyChangeListener listener)
  {
    super(listener);
    this.propertyName = propertyName;
  }

  /**
   * Forwards the event on to the delegate if the property name matches.
   *
   * @param event the event to pass on, if it meets the filter
   * @throws NullPointerException if the delegate this was created with is null
   */
  public void propertyChange(PropertyChangeEvent event)
  {
    // Note: Sun does not filter, under the assumption that since
    // PropertyChangeSupport unwraps proxys, this method should never be
    // called by normal use of listeners.
    String name = event == null ? null : event.getPropertyName();
    if (name == null ? propertyName == null : name.equals(propertyName))
      ((PropertyChangeListener) getListener()).propertyChange(event);
  }

  /**
   * Gets the name of the property this proxy is filtering on.
   *
   * @return the property name
   */
  public String getPropertyName()
  {
    return propertyName;
  }
} // class PropertyChangeListenerProxy