propertychangeevent.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 110 行

/*
 * @(#)PropertyChangeEvent.java	1.21 97/01/03  
 * 
 * Copyright (c) 1996 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 * 
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * 
 * CopyrightVersion bdk_beta
 * 
 */

package java.beans;

/**
 * A "PropertyChange" event gets delivered whenever a bean changes a "bound"
 * or "constrained" property.  A PropertyChangeEvent object is sent as an
 * argument to the PropertyChangeListener and VetoableChangeListener methods.
 * <P>
 * Normally PropertyChangeEvents are accompanied by the name and the old
 * and new value of the changed property.  If the new value is a builtin
 * type (such as int or boolean) it must be wrapped as the 
 * corresponding java.lang.* Object type (such as Integer or Boolean).
 * <P>
 * Null values may be provided for the old and the new values if their
 * true values are not known.
 * <P>
 * An event source may send a null object as the name to indicate that an
 * arbitrary set of if its properties have changed.  In this case the
 * old and new values should also be null.
 */

public class PropertyChangeEvent extends java.util.EventObject {

    /**
     * @param source  The bean that fired the event.
     * @param propertyName  The programmatic name of the property
     *		that was changed.
     * @param oldValue  The old value of the property.
     * @param newValue  The new value of the property.
     */
    public PropertyChangeEvent(Object source, String propertyName,
				     Object oldValue, Object newValue) {
	super(source);
	this.propertyName = propertyName;
	this.newValue = newValue;
	this.oldValue = oldValue;
    }

    /**
     * @return  The programmatic name of the property that was changed.
     *		May be null if multiple properties have changed.
     */
    public String getPropertyName() {
	return propertyName;
    }
    
    /**
     * @return  The new value for the property, expressed as an Object.
     *		May be null if multiple properties have changed.
     */
    public Object getNewValue() {
	return newValue;
    }

    /**
     * @return  The old value for the property, expressed as an Object.
     *		May be null if multiple properties have changed.
     */
    public Object getOldValue() {
	return oldValue;
    }

    /**
     * @param propagationId  The propagationId object for the event.
     */
    public void setPropagationId(Object propagationId) {
	this.propagationId = propagationId;
    }

    /**
     * The "propagationId" field is reserved for future use.  In Beans 1.0
     * the sole requirement is that if a listener catches a PropertyChangeEvent
     * and then fires a PropertyChangeEvent of its own, then it should
     * make sure that it propagates the propagationId field from its
     * incoming event to its outgoing event.
     *
     * @return the propagationId object associated with a bound/constrained
     *		property update.
     */
    public Object getPropagationId() {
	return propagationId;
    }

    private String propertyName;
    private Object newValue;
    private Object oldValue;
    private Object propagationId;
}