Source for java.beans.PropertyChangeEvent

   1: /* PropertyChangeEvent.java -- describes a change in a property
   2:    Copyright (C) 1998, 2000, 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.EventObject;
  42: 
  43: /**
  44:  * PropertyChangeEvents are fired in the PropertyChange and VetoableChange
  45:  * event classes.  They represent the old and new values as well as the
  46:  * source Bean. If the old or new value is a primitive type, it must be
  47:  * wrapped in the appropriate wrapper type (java.lang.Integer for int, etc.,
  48:  * etc.).
  49:  *
  50:  * <p>If the old or new values are unknown (although why that would be I do
  51:  * not know), they may be null. Also, if the set of properties itself has
  52:  * changed, the name should be null, and the old and new values may also be
  53:  * null. Right now Sun put in a propagationId, reserved for future use. Read
  54:  * the comments on the constructor and on setPropagationId for more
  55:  * information.
  56:  *
  57:  * @author John Keiser
  58:  * @author Eric Blake (ebb9@email.byu.edu)
  59:  * @since 1.1
  60:  * @status udpated to 1.4
  61:  */
  62: public class PropertyChangeEvent extends EventObject
  63: {
  64:   /**
  65:    * Compatible with JDK 1.1+.
  66:    */
  67:   private static final long serialVersionUID = 7042693688939648123L;
  68: 
  69:   /**
  70:    * The name of the property that changed, may be null. Package visible for
  71:    * use by PropertyChangeSupport.
  72:    *
  73:    * @serial the changed property name
  74:    */
  75:   final String propertyName;
  76: 
  77:   /**
  78:    * The new value of the property, may be null. Package visible for use by
  79:    * PropertyChangeSupport.
  80:    *
  81:    * @serial the new property value
  82:    */
  83:   final Object newValue;
  84: 
  85:   /**
  86:    * The old value of the property, may be null. Package visible for use by
  87:    * PropertyChangeSupport.
  88:    *
  89:    * @serial the old property value
  90:    */
  91:   final Object oldValue;
  92: 
  93:   /**
  94:    * The propagation ID, reserved for future use. May be null.
  95:    *
  96:    * @see #getPropagationId()
  97:    * @serial the Propagation ID
  98:    */
  99:   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