001    // Copyright 2004, 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry.event;
016    
017    import java.util.EventObject;
018    
019    import org.apache.hivemind.util.Defense;
020    import org.apache.tapestry.IComponent;
021    
022    /**
023     * Event which describes a change to a particular {@link IComponent}.
024     * 
025     * @author Howard Ship
026     */
027    
028    public class ObservedChangeEvent extends EventObject
029    {
030    
031        private static final long serialVersionUID = -7693394232554811975L;
032    
033        private IComponent _component;
034    
035        private String _propertyName;
036    
037        private Object _newValue;
038    
039        /**
040         * Creates the event. The new value must be null, or be a serializable
041         * object. (It is declared as Object as a concession to the Java 2
042         * collections framework, where the implementations are serializable but the
043         * interfaces (Map, List, etc.) don't extend Serializable ... so we wait
044         * until runtime to check).
045         * 
046         * @param component
047         *            The component (not necessarily a page) whose property changed.
048         * @param propertyName
049         *            the name of the property which was changed.
050         * @param newValue
051         *            The new value of the property.
052         * @throws IllegalArgumentException
053         *             if propertyName is null, or if the new value is not
054         *             serializable
055         */
056    
057        public ObservedChangeEvent(IComponent component, String propertyName, Object newValue)
058        {
059            super(component);
060    
061            Defense.notNull(propertyName, "propertyName");
062    
063            _component = component;
064            _propertyName = propertyName;
065            _newValue = newValue;
066        }
067    
068        public IComponent getComponent()
069        {
070            return _component;
071        }
072    
073        public Object getNewValue()
074        {
075            return _newValue;
076        }
077    
078        public String getPropertyName()
079        {
080            return _propertyName;
081        }
082    
083    }