Source for java.beans.PropertyChangeListenerProxy

   1: /* PropertyChangeListenerProxy.java -- adds a name to a property listener
   2:    Copyright (C) 2002, 2005  Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package java.beans;
  40: 
  41: import java.util.EventListenerProxy;
  42: 
  43: /**
  44:  * This class provides an extension to <code>PropertyChangeListener</code> -
  45:  * associating a name with the listener. This can be used to filter the
  46:  * changes that one is interested in.
  47:  *
  48:  * @author Eric Blake (ebb9@email.byu.edu)
  49:  * @since 1.4
  50:  * @status udpated to 1.4
  51:  */
  52: public class PropertyChangeListenerProxy extends EventListenerProxy
  53:   implements PropertyChangeListener
  54: {
  55:   /**
  56:    * The name of the property to listen for. Package visible for use by
  57:    * PropertyChangeSupport.
  58:    */
  59:   final String propertyName;
  60: 
  61:   /**
  62:    * Create a new proxy which filters property change events and only passes
  63:    * changes to the named property on to the delegate. A null propertyName
  64:    * or listener does not fail now, but may cause a NullPointerException down
  65:    * the road.
  66:    *
  67:    * @param propertyName the property's name to filter on
  68:    * @param listener the delegate listener
  69:    */
  70:   public PropertyChangeListenerProxy(String propertyName,
  71:                                      PropertyChangeListener listener)
  72:   {
  73:     super(listener);
  74:     this.propertyName = propertyName;
  75:   }
  76: 
  77:   /**
  78:    * Forwards the event on to the delegate if the property name matches.
  79:    *
  80:    * @param event the event to pass on, if it meets the filter
  81:    * @throws NullPointerException if the delegate this was created with is null
  82:    */
  83:   public void propertyChange(PropertyChangeEvent event)
  84:   {
  85:     // Note: Sun does not filter, under the assumption that since
  86:     // PropertyChangeSupport unwraps proxys, this method should never be
  87:     // called by normal use of listeners.
  88:     String name = event == null ? null : event.getPropertyName();
  89:     if (name == null ? propertyName == null : name.equals(propertyName))
  90:       ((PropertyChangeListener) getListener()).propertyChange(event);
  91:   }
  92: 
  93:   /**
  94:    * Gets the name of the property this proxy is filtering on.
  95:    *
  96:    * @return the property name
  97:    */
  98:   public String getPropertyName()
  99:   {
 100:     return propertyName;
 101:   }
 102: } // class PropertyChangeListenerProxy