001/*
002 * Copyright 2002-2017 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.servlet.handler;
018
019import javax.servlet.http.HttpServletRequest;
020import javax.servlet.http.HttpServletResponse;
021
022import org.springframework.lang.Nullable;
023import org.springframework.web.method.HandlerMethod;
024import org.springframework.web.servlet.ModelAndView;
025
026/**
027 * Abstract base class for
028 * {@link org.springframework.web.servlet.HandlerExceptionResolver HandlerExceptionResolver}
029 * implementations that support handling exceptions from handlers of type {@link HandlerMethod}.
030 *
031 * @author Rossen Stoyanchev
032 * @since 3.1
033 */
034public abstract class AbstractHandlerMethodExceptionResolver extends AbstractHandlerExceptionResolver {
035
036        /**
037         * Checks if the handler is a {@link HandlerMethod} and then delegates to the
038         * base class implementation of {@code #shouldApplyTo(HttpServletRequest, Object)}
039         * passing the bean of the {@code HandlerMethod}. Otherwise returns {@code false}.
040         */
041        @Override
042        protected boolean shouldApplyTo(HttpServletRequest request, @Nullable Object handler) {
043                if (handler == null) {
044                        return super.shouldApplyTo(request, null);
045                }
046                else if (handler instanceof HandlerMethod) {
047                        HandlerMethod handlerMethod = (HandlerMethod) handler;
048                        handler = handlerMethod.getBean();
049                        return super.shouldApplyTo(request, handler);
050                }
051                else {
052                        return false;
053                }
054        }
055
056        @Override
057        @Nullable
058        protected final ModelAndView doResolveException(
059                        HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex) {
060
061                return doResolveHandlerMethodException(request, response, (HandlerMethod) handler, ex);
062        }
063
064        /**
065         * Actually resolve the given exception that got thrown during on handler execution,
066         * returning a ModelAndView that represents a specific error page if appropriate.
067         * <p>May be overridden in subclasses, in order to apply specific exception checks.
068         * Note that this template method will be invoked <i>after</i> checking whether this
069         * resolved applies ("mappedHandlers" etc), so an implementation may simply proceed
070         * with its actual exception handling.
071         * @param request current HTTP request
072         * @param response current HTTP response
073         * @param handlerMethod the executed handler method, or {@code null} if none chosen at the time
074         * of the exception (for example, if multipart resolution failed)
075         * @param ex the exception that got thrown during handler execution
076         * @return a corresponding ModelAndView to forward to, or {@code null} for default processing
077         */
078        @Nullable
079        protected abstract ModelAndView doResolveHandlerMethodException(
080                        HttpServletRequest request, HttpServletResponse response, @Nullable HandlerMethod handlerMethod, Exception ex);
081
082}