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
005// http://www.apache.org/licenses/LICENSE-2.0
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.
013package org.apache.tapestry5;
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>
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);