001    // Copyright 2006, 2008 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.tapestry5.internal.util;
016    
017    import org.apache.tapestry5.ComponentEventCallback;
018    
019    /**
020     * A {@link org.apache.tapestry5.ComponentEventCallback} used for notification events. Event handler methods may return
021     * true (to abort the event) or false (to allow the event to continue bubbling up), but all other values are forbidden.
022     */
023    public class NotificationEventCallback implements ComponentEventCallback
024    {
025        private final String eventType;
026    
027        private final String completeId;
028    
029        public NotificationEventCallback(String eventType, String completeId)
030        {
031            this.eventType = eventType;
032            this.completeId = completeId;
033        }
034    
035        public boolean handleResult(Object result)
036        {
037            if (result instanceof Boolean) return ((Boolean) result);
038    
039            throw new IllegalArgumentException(
040                    UtilMessages.noReturnValueAccepted(eventType, completeId, result));
041        }
042    
043    }