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.services;
014
015import org.apache.tapestry5.ExceptionHandlerAssistant;
016import org.apache.tapestry5.ioc.annotations.UsesMappedConfiguration;
017
018import java.io.IOException;
019
020/**
021 * Service invoked when an uncaught exception occurs. The error handler is responsible for providing a response to the
022 * user to describe the error.
023 *
024 * The default implementation accepts the configuration, which maps an exception class to a corresponding helper.
025 * The helper is either an instance of {@link ExceptionHandlerAssistant} or is a Class for a page that will be redirected
026 * to, to present the exception.
027 */
028@UsesMappedConfiguration(key = Class.class, value = Object.class)
029public interface RequestExceptionHandler
030{
031    /**
032     * Responsible for handling the error <em>in some way</em> and providing <em>some response</em> to the client. A
033     * default implementation may render an error response page.
034     *
035     *
036     * The handler is also responsible for setting the response status and the X-Tapestry-ErrorMessage response header.
037     * These are very important in Ajax requests to allow the client-side logic to detect the error and present it to
038     * the user.
039     *
040     * @param exception
041     *         uncaught exception to be reported
042     * @throws IOException
043     */
044    void handleRequestException(Throwable exception) throws IOException;
045}