001// Copyright 2006, 2008, 2010 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
015package org.apache.tapestry5;
016
017/**
018 * Callback interface for a {@linkplain org.apache.tapestry5.runtime.Event render phase event} or
019 * 
020 * {@link org.apache.tapestry5.runtime.ComponentEvent}, notified when a non-null value is returned from some event
021 *       handler method.
022 */
023public interface ComponentEventCallback<T>
024{
025    /**
026     * Invoked to handle a non-null event handler method result. The handler should determine whether the value is
027     * acceptable, and throw an exception if not. Any thrown exception will be wrapped to identify the component and
028     * method from which the value was returned.
029     * <p/>
030     * Boolean values are <em>not</em> passed to the callback. Booleans are used to indicate that the event has been
031     * handled (true, meaning the event is handled and aborted) or that a further search for handlers should continue
032     * (false, meaning the event was not handled, is not aborted, and the search up the component hierarchy for event
033     * handler methods should continue). If a component event method returns true, then
034     * {@link org.apache.tapestry5.runtime.Event#isAborted()} will return true.
035     * 
036     * @param result
037     *            the result value returned from the event handler method
038     * @return true if the event is aborted, false if the event may continue
039     */
040    boolean handleResult(T result);
041}