001    /* PropertyChangeEvent.java -- describes a change in a property
002       Copyright (C) 1998, 2000, 2002, 2005  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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
023    conditions of the GNU General Public License cover the whole
024    combination.
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
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package java.beans;
040    
041    import java.util.EventObject;
042    
043    /**
044     * PropertyChangeEvents are fired in the PropertyChange and VetoableChange
045     * event classes.  They represent the old and new values as well as the
046     * source Bean. If the old or new value is a primitive type, it must be
047     * wrapped in the appropriate wrapper type (java.lang.Integer for int, etc.,
048     * etc.).
049     *
050     * <p>If the old or new values are unknown (although why that would be I do
051     * not know), they may be null. Also, if the set of properties itself has
052     * changed, the name should be null, and the old and new values may also be
053     * null. Right now Sun put in a propagationId, reserved for future use. Read
054     * the comments on the constructor and on setPropagationId for more
055     * information.
056     *
057     * @author John Keiser
058     * @author Eric Blake (ebb9@email.byu.edu)
059     * @since 1.1
060     * @status udpated to 1.4
061     */
062    public class PropertyChangeEvent extends EventObject
063    {
064      /**
065       * Compatible with JDK 1.1+.
066       */
067      private static final long serialVersionUID = 7042693688939648123L;
068    
069      /**
070       * The name of the property that changed, may be null. Package visible for
071       * use by PropertyChangeSupport.
072       *
073       * @serial the changed property name
074       */
075      final String propertyName;
076    
077      /**
078       * The new value of the property, may be null. Package visible for use by
079       * PropertyChangeSupport.
080       *
081       * @serial the new property value
082       */
083      final Object newValue;
084    
085      /**
086       * The old value of the property, may be null. Package visible for use by
087       * PropertyChangeSupport.
088       *
089       * @serial the old property value
090       */
091      final Object oldValue;
092    
093      /**
094       * The propagation ID, reserved for future use. May be null.
095       *
096       * @see #getPropagationId()
097       * @serial the Propagation ID
098       */
099      private Object propagationId;
100    
101      /**
102       * Create a new PropertyChangeEvent. Remember that if you received a
103       * PropertyChangeEvent and are sending a new one, you should also set the
104       * propagation ID from the old PropertyChangeEvent.
105       *
106       * @param source the Bean containing the property
107       * @param propertyName the property's name
108       * @param oldVal the old value of the property
109       * @param newVal the new value of the property
110       * @throws IllegalArgumentException if source is null
111       */
112      public PropertyChangeEvent(Object source, String propertyName,
113                                 Object oldVal, Object newVal)
114      {
115        super(source);
116        this.propertyName = propertyName;
117        oldValue = oldVal;
118        newValue = newVal;
119      }
120    
121      /**
122       * Get the property name. May be null if multiple properties changed.
123       *
124       * @return the property name
125       */
126      public String getPropertyName()
127      {
128        return propertyName;
129      }
130    
131      /**
132       * Get the property's new value. May be null if multiple properties changed.
133       *
134       * @return the property's new value
135       */
136      public Object getNewValue()
137      {
138        return newValue;
139      }
140    
141      /**
142       * Get the property's old value. May be null if multiple properties changed.
143       *
144       * @return the property's old value
145       */
146      public Object getOldValue()
147      {
148        return oldValue;
149      }
150    
151      /**
152       * Set the propagation ID.  This is a way for the event to be passed from
153       * hand to hand and retain a little extra state.  Right now it is unused,
154       * but it should be propagated anyway so that future versions of JavaBeans
155       * can use it, for God knows what.
156       *
157       * @param propagationId the propagation ID
158       * @see #getPropagationId()
159       */
160      public void setPropagationId(Object propagationId)
161      {
162        this.propagationId = propagationId;
163      }
164    
165      /**
166       * Get the propagation ID. Right now, it is not used for anything.
167       *
168       * @return the propagation ID
169       * @see #setPropagationId(Object)
170       */
171      public Object getPropagationId()
172      {
173        return propagationId;
174      }
175    
176      /**
177       * Utility method to rollback a change.
178       *
179       * @param event the event to rollback
180       * @return a new event with old and new swapped
181       */
182      PropertyChangeEvent rollback()
183      {
184        PropertyChangeEvent result
185          = new PropertyChangeEvent(source, propertyName, newValue, oldValue);
186        result.propagationId = propagationId;
187        return result;
188      }
189    } // class PropertyChangeEvent