/* VetoableChangeListener.java -- listen for a change which can be vetoed
   Copyright (C) 1998, 2000, 2002 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package java.beans;

import java.util.EventListener;

/**
 * VetoableChangeListener allows a class to monitor proposed changes to
 * properties of a Bean and, if desired, prevent them from occurring. A
 * vetoableChange() event will be fired <em>after</em> the property change has
 * been requested, but before it is permanent. If any listener rejects the
 * change by throwing the PropertyChangeException, a new vetoableChange()
 * event will be fired to all listeners who received a vetoableChange() event
 * in the first place, informing them to revert back to the old value. Thus,
 * the listener that threw the exception the first time should be prepared
 * to rethrow it the second time. The value, of course, never actually changed.
 *
 * <p><strong>Note:</strong> This class may not be reliably used to determine
 * whether a property has actually changed.  Use the PropertyChangeListener
 * interface for that instead.
 *
 * @author John Keiser
 * @see java.beans.PropertyChangeListener
 * @see java.beans.VetoableChangeSupport
 * @since 1.1
 * @status updated to 1.4
 */
public interface VetoableChangeListener extends EventListener
{
  /**
   * Fired before a Bean's property changes.
   *
   * @param e the change (containing the old and new values)
   * @throws PropertyVetoException if the change is vetoed by the listener
   */
  void vetoableChange(PropertyChangeEvent e) throws PropertyVetoException;
} // interface VetoableChangeListener