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
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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.
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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
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