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jlechner |
/* PropertyChangeEvent.java -- describes a change in a property
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Copyright (C) 1998, 2000, 2002, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.beans;
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import java.util.EventObject;
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/**
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* PropertyChangeEvents are fired in the PropertyChange and VetoableChange
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* event classes. They represent the old and new values as well as the
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* source Bean. If the old or new value is a primitive type, it must be
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* wrapped in the appropriate wrapper type (java.lang.Integer for int, etc.,
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* etc.).
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*
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* <p>If the old or new values are unknown (although why that would be I do
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* not know), they may be null. Also, if the set of properties itself has
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* changed, the name should be null, and the old and new values may also be
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* null. Right now Sun put in a propagationId, reserved for future use. Read
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* the comments on the constructor and on setPropagationId for more
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* information.
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*
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* @author John Keiser
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* @author Eric Blake (ebb9@email.byu.edu)
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* @since 1.1
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* @status udpated to 1.4
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*/
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public class PropertyChangeEvent extends EventObject
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{
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/**
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* Compatible with JDK 1.1+.
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*/
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private static final long serialVersionUID = 7042693688939648123L;
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/**
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* The name of the property that changed, may be null. Package visible for
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* use by PropertyChangeSupport.
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*
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* @serial the changed property name
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*/
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final String propertyName;
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/**
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* The new value of the property, may be null. Package visible for use by
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* PropertyChangeSupport.
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*
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* @serial the new property value
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*/
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final Object newValue;
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/**
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* The old value of the property, may be null. Package visible for use by
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* PropertyChangeSupport.
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*
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* @serial the old property value
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*/
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final Object oldValue;
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/**
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* The propagation ID, reserved for future use. May be null.
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*
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* @see #getPropagationId()
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* @serial the Propagation ID
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*/
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private Object propagationId;
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/**
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* Create a new PropertyChangeEvent. Remember that if you received a
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* PropertyChangeEvent and are sending a new one, you should also set the
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* propagation ID from the old PropertyChangeEvent.
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*
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* @param source the Bean containing the property
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* @param propertyName the property's name
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* @param oldVal the old value of the property
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* @param newVal the new value of the property
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* @throws IllegalArgumentException if source is null
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*/
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public PropertyChangeEvent(Object source, String propertyName,
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Object oldVal, Object newVal)
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{
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super(source);
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this.propertyName = propertyName;
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oldValue = oldVal;
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newValue = newVal;
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}
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/**
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* Get the property name. May be null if multiple properties changed.
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*
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* @return the property name
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*/
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public String getPropertyName()
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{
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return propertyName;
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}
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/**
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* Get the property's new value. May be null if multiple properties changed.
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*
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* @return the property's new value
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*/
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public Object getNewValue()
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{
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return newValue;
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}
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/**
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* Get the property's old value. May be null if multiple properties changed.
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*
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* @return the property's old value
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*/
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public Object getOldValue()
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{
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return oldValue;
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}
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/**
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* Set the propagation ID. This is a way for the event to be passed from
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* hand to hand and retain a little extra state. Right now it is unused,
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* but it should be propagated anyway so that future versions of JavaBeans
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* can use it, for God knows what.
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*
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* @param propagationId the propagation ID
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* @see #getPropagationId()
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*/
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public void setPropagationId(Object propagationId)
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{
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this.propagationId = propagationId;
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}
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/**
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* Get the propagation ID. Right now, it is not used for anything.
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*
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* @return the propagation ID
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* @see #setPropagationId(Object)
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*/
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public Object getPropagationId()
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{
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return propagationId;
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}
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/**
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* Utility method to rollback a change.
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*
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* @param event the event to rollback
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* @return a new event with old and new swapped
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*/
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PropertyChangeEvent rollback()
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{
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PropertyChangeEvent result
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= new PropertyChangeEvent(source, propertyName, newValue, oldValue);
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result.propagationId = propagationId;
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return result;
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}
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} // class PropertyChangeEvent
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