001/* PropertyChangeEvent.java -- describes a change in a property 002 Copyright (C) 1998, 2000, 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.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 */ 062public 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