    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005// http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5;
    014
    015/**
    016 * Callback interface for a {@linkplain org.apache.tapestry5.runtime.Event render phase event} or
    017 *
    018 * {@link org.apache.tapestry5.runtime.ComponentEvent}, notified when a non-null value is returned from some event
    019 *       handler method.
    020 */
    021public interface ComponentEventCallback<T>
    022{
    023    /**
    024     * Invoked to handle a non-null event handler method result. The handler should determine whether the value is
    025     * acceptable, and throw an exception if not. Any thrown exception will be wrapped to identify the component and
    026     * method from which the value was returned.
    027     *
    028     * Boolean values are <em>not</em> passed to the callback. Booleans are used to indicate that the event has been
    029     * handled (true, meaning the event is handled and aborted) or that a further search for handlers should continue
    030     * (false, meaning the event was not handled, is not aborted, and the search up the component hierarchy for event
    031     * handler methods should continue). If a component event method returns true, then
    032     * {@link org.apache.tapestry5.runtime.Event#isAborted()} will return true.
    033     *
    034     * @param result
    035     *            the result value returned from the event handler method
    036     * @return true if the event is aborted, false if the event may continue
    037     */
    038    boolean handleResult(T result);
    039}