1 /*
   2  * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.beans;
  27 
  28 import java.util.EventObject;
  29 
  30 /**
  31  * A "PropertyChange" event gets delivered whenever a bean changes a "bound"
  32  * or "constrained" property.  A PropertyChangeEvent object is sent as an
  33  * argument to the PropertyChangeListener and VetoableChangeListener methods.
  34  * <P>
  35  * Normally PropertyChangeEvents are accompanied by the name and the old
  36  * and new value of the changed property.  If the new value is a primitive
  37  * type (such as int or boolean) it must be wrapped as the
  38  * corresponding java.lang.* Object type (such as Integer or Boolean).
  39  * <P>
  40  * Null values may be provided for the old and the new values if their
  41  * true values are not known.
  42  * <P>
  43  * An event source may send a null object as the name to indicate that an
  44  * arbitrary set of if its properties have changed.  In this case the
  45  * old and new values should also be null.
  46  */
  47 public class PropertyChangeEvent extends EventObject {
  48     private static final long serialVersionUID = 7042693688939648123L;
  49 
  50     /**
  51      * Constructs a new {@code PropertyChangeEvent}.
  52      *
  53      * @param source        the bean that fired the event
  54      * @param propertyName  the programmatic name of the property that was changed
  55      * @param oldValue      the old value of the property
  56      * @param newValue      the new value of the property
  57      *
  58      * @throws IllegalArgumentException if {@code source} is {@code null}
  59      */
  60     public PropertyChangeEvent(Object source, String propertyName,
  61                                Object oldValue, Object newValue) {
  62         super(source);
  63         this.propertyName = propertyName;
  64         this.newValue = newValue;
  65         this.oldValue = oldValue;
  66     }
  67 
  68     /**
  69      * Gets the programmatic name of the property that was changed.
  70      *
  71      * @return  The programmatic name of the property that was changed.
  72      *          May be null if multiple properties have changed.
  73      */
  74     public String getPropertyName() {
  75         return propertyName;
  76     }
  77 
  78     /**
  79      * Gets the new value for the property, expressed as an Object.
  80      *
  81      * @return  The new value for the property, expressed as an Object.
  82      *          May be null if multiple properties have changed.
  83      */
  84     public Object getNewValue() {
  85         return newValue;
  86     }
  87 
  88     /**
  89      * Gets the old value for the property, expressed as an Object.
  90      *
  91      * @return  The old value for the property, expressed as an Object.
  92      *          May be null if multiple properties have changed.
  93      */
  94     public Object getOldValue() {
  95         return oldValue;
  96     }
  97 
  98     /**
  99      * Sets the propagationId object for the event.
 100      *
 101      * @param propagationId  The propagationId object for the event.
 102      */
 103     public void setPropagationId(Object propagationId) {
 104         this.propagationId = propagationId;
 105     }
 106 
 107     /**
 108      * The "propagationId" field is reserved for future use.  In Beans 1.0
 109      * the sole requirement is that if a listener catches a PropertyChangeEvent
 110      * and then fires a PropertyChangeEvent of its own, then it should
 111      * make sure that it propagates the propagationId field from its
 112      * incoming event to its outgoing event.
 113      *
 114      * @return the propagationId object associated with a bound/constrained
 115      *          property update.
 116      */
 117     public Object getPropagationId() {
 118         return propagationId;
 119     }
 120 
 121     /**
 122      * name of the property that changed.  May be null, if not known.
 123      * @serial
 124      */
 125     private String propertyName;
 126 
 127     /**
 128      * New value for property.  May be null if not known.
 129      * @serial
 130      */
 131     private Object newValue;
 132 
 133     /**
 134      * Previous value for property.  May be null if not known.
 135      * @serial
 136      */
 137     private Object oldValue;
 138 
 139     /**
 140      * Propagation ID.  May be null.
 141      * @serial
 142      * @see #getPropagationId
 143      */
 144     private Object propagationId;
 145 
 146     /**
 147      * Returns a string representation of the object.
 148      *
 149      * @return a string representation of the object
 150      *
 151      * @since 1.7
 152      */
 153     public String toString() {
 154         StringBuilder sb = new StringBuilder(getClass().getName());
 155         sb.append("[propertyName=").append(getPropertyName());
 156         appendTo(sb);
 157         sb.append("; oldValue=").append(getOldValue());
 158         sb.append("; newValue=").append(getNewValue());
 159         sb.append("; propagationId=").append(getPropagationId());
 160         sb.append("; source=").append(getSource());
 161         return sb.append("]").toString();
 162     }
 163 
 164     void appendTo(StringBuilder sb) {
 165     }
 166 }