    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}