Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.wicket; import org.apache.wicket.authorization.AuthorizationException; import org.apache.wicket.core.request.handler.IPageRequestHandler; import org.apache.wicket.core.request.handler.ListenerInvocationNotAllowedException; import org.apache.wicket.core.request.handler.PageProvider; import org.apache.wicket.core.request.handler.RenderPageRequestHandler; import org.apache.wicket.core.request.mapper.StalePageException; import org.apache.wicket.markup.html.pages.ExceptionErrorPage; import org.apache.wicket.protocol.http.PageExpiredException; import org.apache.wicket.protocol.http.servlet.ResponseIOException; import org.apache.wicket.request.IExceptionMapper; import org.apache.wicket.request.IRequestHandler; import org.apache.wicket.request.Request; import org.apache.wicket.request.Response; import org.apache.wicket.request.cycle.RequestCycle; import org.apache.wicket.request.handler.EmptyRequestHandler; import org.apache.wicket.request.http.WebRequest; import org.apache.wicket.request.http.WebResponse; import org.apache.wicket.request.http.handler.ErrorCodeRequestHandler; import org.apache.wicket.request.resource.PackageResource; import org.apache.wicket.settings.ExceptionSettings; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * If an exception is thrown when a page is being rendered this mapper will decide which error page * to show depending on the exception type and {@link Application#getExceptionSettings() application * configuration} */ public class DefaultExceptionMapper implements IExceptionMapper { private static final Logger logger = LoggerFactory.getLogger(DefaultExceptionMapper.class); @Override public IRequestHandler map(Exception e) { try { Response response = RequestCycle.get().getResponse(); if (response instanceof WebResponse) { // we don't want to cache an exceptional reply in the browser ((WebResponse) response).disableCaching(); } return internalMap(e); } catch (RuntimeException e2) { if (logger.isDebugEnabled()) { logger.error("An error occurred while handling a previous error: " + e2.getMessage(), e2); } // hmmm, we were already handling an exception! give up logger.error("unexpected exception when handling another exception: " + e.getMessage(), e); return new ErrorCodeRequestHandler(500); } } /** * Maps exceptions to their corresponding {@link IRequestHandler}. * * @param e * the current exception * @return the {@link IRequestHandler} for the current exception */ private IRequestHandler internalMap(Exception e) { final Application application = Application.get(); // check if we are processing an Ajax request and if we want to invoke the failure handler if (isProcessingAjaxRequest()) { switch (application.getExceptionSettings().getAjaxErrorHandlingStrategy()) { case INVOKE_FAILURE_HANDLER: return new ErrorCodeRequestHandler(500); } } IRequestHandler handleExpectedExceptions = mapExpectedExceptions(e, application); if (handleExpectedExceptions != null) { return handleExpectedExceptions; } return mapUnexpectedExceptions(e, application); } /** * Maps expected exceptions (i.e. those internally used by Wicket) to their corresponding * {@link IRequestHandler}. * * @param e * the current exception * @param application * the current application object * @return the {@link IRequestHandler} for the current exception */ protected IRequestHandler mapExpectedExceptions(Exception e, final Application application) { if (e instanceof StalePageException) { // If the page was stale, just re-render it // (the url should always be updated by an redirect in that case) return new RenderPageRequestHandler(new PageProvider(((StalePageException) e).getPage())); } else if (e instanceof PageExpiredException) { return createPageRequestHandler( new PageProvider(Application.get().getApplicationSettings().getPageExpiredErrorPage())); } else if (e instanceof AuthorizationException || e instanceof ListenerInvocationNotAllowedException) { return createPageRequestHandler( new PageProvider(Application.get().getApplicationSettings().getAccessDeniedPage())); } else if (e instanceof ResponseIOException) { logger.debug("Connection lost, give up responding.", e); return new EmptyRequestHandler(); } else if (e instanceof PackageResource.PackageResourceBlockedException && application.usesDeploymentConfig()) { logger.debug(e.getMessage(), e); return new ErrorCodeRequestHandler(404); } return null; } /** * Maps unexpected exceptions to their corresponding {@link IRequestHandler}. * * @param e * the current exception * @param application * the current application object * @return the {@link IRequestHandler} for the current exception */ protected IRequestHandler mapUnexpectedExceptions(Exception e, final Application application) { final ExceptionSettings.UnexpectedExceptionDisplay unexpectedExceptionDisplay = application .getExceptionSettings().getUnexpectedExceptionDisplay(); logger.error("Unexpected error occurred", e); if (ExceptionSettings.SHOW_EXCEPTION_PAGE.equals(unexpectedExceptionDisplay)) { Page currentPage = extractCurrentPage(); return createPageRequestHandler(new PageProvider(new ExceptionErrorPage(e, currentPage))); } else if (ExceptionSettings.SHOW_INTERNAL_ERROR_PAGE.equals(unexpectedExceptionDisplay)) { return createPageRequestHandler( new PageProvider(application.getApplicationSettings().getInternalErrorPage())); } // IExceptionSettings.SHOW_NO_EXCEPTION_PAGE return new ErrorCodeRequestHandler(500); } /** * Creates a {@link RenderPageRequestHandler} for the target page provided by {@code pageProvider}. * * Uses {@link RenderPageRequestHandler.RedirectPolicy#NEVER_REDIRECT} policy to preserve the original page's URL * for non-Ajax requests and {@link RenderPageRequestHandler.RedirectPolicy#AUTO_REDIRECT} for AJAX requests. * * @param pageProvider * the page provider for the target page * @return the request handler for the target page */ protected RenderPageRequestHandler createPageRequestHandler(PageProvider pageProvider) { RequestCycle requestCycle = RequestCycle.get(); if (requestCycle == null) { throw new IllegalStateException("there is no current request cycle attached to this thread"); } RenderPageRequestHandler.RedirectPolicy redirect = RenderPageRequestHandler.RedirectPolicy.NEVER_REDIRECT; if (isProcessingAjaxRequest()) { redirect = RenderPageRequestHandler.RedirectPolicy.AUTO_REDIRECT; } return new RenderPageRequestHandler(pageProvider, redirect); } /** * @return true if current request is an AJAX request, false otherwise. */ protected boolean isProcessingAjaxRequest() { RequestCycle rc = RequestCycle.get(); Request request = rc.getRequest(); if (request instanceof WebRequest) { return ((WebRequest) request).isAjax(); } return false; } /** * @return the page being rendered when the exception was thrown, or {@code null} if it cannot * be extracted */ protected Page extractCurrentPage() { final RequestCycle requestCycle = RequestCycle.get(); IRequestHandler handler = requestCycle.getActiveRequestHandler(); if (handler == null) { handler = requestCycle.getRequestHandlerScheduledAfterCurrent(); } if (handler instanceof IPageRequestHandler) { IPageRequestHandler pageRequestHandler = (IPageRequestHandler) handler; return (Page) pageRequestHandler.getPage(); } return null; } }