001 /* PropertyChangeListenerProxy.java -- adds a name to a property listener
002 Copyright (C) 2002, 2005 Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
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009 any later version.
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014 General Public License for more details.
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019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
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025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
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036 exception statement from your version. */
037
038
039 package java.beans;
040
041 import 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 */
052 public 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