001/* VetoableChangeListenerProxy.java -- adds a name to a vetoable listener
002   Copyright (C) 2002, 2005  Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package java.beans;
040
041import java.util.EventListenerProxy;
042
043/**
044 * This class provides an extension to <code>VetoableChangeListener</code> -
045 * associating a name with the listener. This can be used to filter the
046 * changes that one is interested in.
047 *
048 * @author Eric Blake (ebb9@email.byu.edu)
049 * @since 1.4
050 * @status udpated to 1.4
051 */
052public class VetoableChangeListenerProxy extends EventListenerProxy
053  implements VetoableChangeListener
054{
055  /**
056   * The name of the property to listen for. Package visible for use by
057   * VetoableChangeSupport.
058   */
059  final String propertyName;
060
061  /**
062   * Create a new proxy which filters property change events and only passes
063   * changes to the named property on to the delegate.
064   *
065   * @param propertyName the property's name to filter on
066   * @param listener the delegate listener
067   */
068  public VetoableChangeListenerProxy(String propertyName,
069                                     VetoableChangeListener listener)
070  {
071    super(listener);
072    this.propertyName = propertyName;
073  }
074
075  /**
076   * Forwards the event on to the delegate if the property name matches.
077   *
078   * @param event the event to pass on, if it meets the filter
079   * @throws NullPointerException if the delegate this was created with is null
080   * @throws PropertyVetoException if the change is vetoed by the listener
081   */
082  public void vetoableChange(PropertyChangeEvent event)
083    throws PropertyVetoException
084  {
085    // Note: Sun does not filter, under the assumption that since
086    // VetoableChangeSupport unwraps proxys, this method should never be
087    // called by normal use of listeners.
088    String name = event == null ? null : event.getPropertyName();
089    if (name == null ? propertyName == null : name.equals(propertyName))
090      ((VetoableChangeListener) getListener()).vetoableChange(event);
091  }
092
093  /**
094   * Gets the name of the property this proxy is filtering on.
095   *
096   * @return the property name
097   */
098  public String getPropertyName()
099  {
100    return propertyName;
101  }
102} // class VetoableChangeListenerProxy