libjava/java/beans/VetoableChangeListener.java

   1 /* VetoableChangeListener.java -- listen for a change which can be vetoed
   2    Copyright (C) 1998, 2000, 2002 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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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.EventListener;
  42
  43 /**
  44  * VetoableChangeListener allows a class to monitor proposed changes to
  45  * properties of a Bean and, if desired, prevent them from occurring. A
  46  * vetoableChange() event will be fired <em>after</em> the property change has
  47  * been requested, but before it is permanent. If any listener rejects the
  48  * change by throwing the PropertyChangeException, a new vetoableChange()
  49  * event will be fired to all listeners who received a vetoableChange() event
  50  * in the first place, informing them to revert back to the old value. Thus,
  51  * the listener that threw the exception the first time should be prepared
  52  * to rethrow it the second time. The value, of course, never actually changed.
  53  *
  54  * <p><strong>Note:</strong> This class may not be reliably used to determine
  55  * whether a property has actually changed.  Use the PropertyChangeListener
  56  * interface for that instead.
  57  *
  58  * @author John Keiser
  59  * @see java.beans.PropertyChangeListener
  60  * @see java.beans.VetoableChangeSupport
  61  * @since 1.1
  62  * @status updated to 1.4
  63  */
  64 public interface VetoableChangeListener extends EventListener
  65 {
  66   /**
  67    * Fired before a Bean's property changes.
  68    *
  69    * @param e the change (containing the old and new values)
  70    * @throws PropertyVetoException if the change is vetoed by the listener
  71    */
  72   void vetoableChange(PropertyChangeEvent e) throws PropertyVetoException;
  73 } // interface VetoableChangeListener