    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
    015    package 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     */
    023    public 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    }