001/* PropertyChangeListenerProxy.java -- adds a name to a property 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>PropertyChangeListener</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 PropertyChangeListenerProxy extends EventListenerProxy 053 implements PropertyChangeListener 054{ 055 /** 056 * The name of the property to listen for. Package visible for use by 057 * PropertyChangeSupport. 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. A null propertyName 064 * or listener does not fail now, but may cause a NullPointerException down 065 * the road. 066 * 067 * @param propertyName the property's name to filter on 068 * @param listener the delegate listener 069 */ 070 public PropertyChangeListenerProxy(String propertyName, 071 PropertyChangeListener listener) 072 { 073 super(listener); 074 this.propertyName = propertyName; 075 } 076 077 /** 078 * Forwards the event on to the delegate if the property name matches. 079 * 080 * @param event the event to pass on, if it meets the filter 081 * @throws NullPointerException if the delegate this was created with is null 082 */ 083 public void propertyChange(PropertyChangeEvent event) 084 { 085 // Note: Sun does not filter, under the assumption that since 086 // PropertyChangeSupport 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 ((PropertyChangeListener) getListener()).propertyChange(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 PropertyChangeListenerProxy