001/*
002 * Copyright 2002-2014 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.method.annotation;
018
019import java.util.ArrayList;
020
021import org.springframework.core.MethodParameter;
022import org.springframework.ui.ModelMap;
023import org.springframework.validation.BindingResult;
024import org.springframework.validation.Errors;
025import org.springframework.web.bind.support.WebDataBinderFactory;
026import org.springframework.web.context.request.NativeWebRequest;
027import org.springframework.web.method.support.HandlerMethodArgumentResolver;
028import org.springframework.web.method.support.ModelAndViewContainer;
029
030/**
031 * Resolves {@link Errors} method arguments.
032 *
033 * <p>An {@code Errors} method argument is expected to appear immediately after
034 * the model attribute in the method signature. It is resolved by expecting the
035 * last two attributes added to the model to be the model attribute and its
036 * {@link BindingResult}.
037 *
038 * @author Rossen Stoyanchev
039 * @since 3.1
040 */
041public class ErrorsMethodArgumentResolver implements HandlerMethodArgumentResolver {
042
043        @Override
044        public boolean supportsParameter(MethodParameter parameter) {
045                Class<?> paramType = parameter.getParameterType();
046                return Errors.class.isAssignableFrom(paramType);
047        }
048
049        @Override
050        public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
051                        NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
052
053                ModelMap model = mavContainer.getModel();
054                if (model.size() > 0) {
055                        int lastIndex = model.size()-1;
056                        String lastKey = new ArrayList<String>(model.keySet()).get(lastIndex);
057                        if (lastKey.startsWith(BindingResult.MODEL_KEY_PREFIX)) {
058                                return model.get(lastKey);
059                        }
060                }
061
062                throw new IllegalStateException(
063                                "An Errors/BindingResult argument is expected to be declared immediately after the model attribute, " +
064                                "the @RequestBody or the @RequestPart arguments to which they apply: " + parameter.getMethod());
065        }
066
067}