001 /* VetoableChangeListener.java -- listen for a change which can be vetoed 002 Copyright (C) 1998, 2000, 2002 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. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 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. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 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.EventListener; 042 043 /** 044 * VetoableChangeListener allows a class to monitor proposed changes to 045 * properties of a Bean and, if desired, prevent them from occurring. A 046 * vetoableChange() event will be fired <em>after</em> the property change has 047 * been requested, but before it is permanent. If any listener rejects the 048 * change by throwing the PropertyChangeException, a new vetoableChange() 049 * event will be fired to all listeners who received a vetoableChange() event 050 * in the first place, informing them to revert back to the old value. Thus, 051 * the listener that threw the exception the first time should be prepared 052 * to rethrow it the second time. The value, of course, never actually changed. 053 * 054 * <p><strong>Note:</strong> This class may not be reliably used to determine 055 * whether a property has actually changed. Use the PropertyChangeListener 056 * interface for that instead. 057 * 058 * @author John Keiser 059 * @see java.beans.PropertyChangeListener 060 * @see java.beans.VetoableChangeSupport 061 * @since 1.1 062 * @status updated to 1.4 063 */ 064 public interface VetoableChangeListener extends EventListener 065 { 066 /** 067 * Fired before a Bean's property changes. 068 * 069 * @param e the change (containing the old and new values) 070 * @throws PropertyVetoException if the change is vetoed by the listener 071 */ 072 void vetoableChange(PropertyChangeEvent e) throws PropertyVetoException; 073 } // interface VetoableChangeListener