001/*
002 * Copyright 2002-2020 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 org.springframework.core.MethodParameter;
020import org.springframework.lang.Nullable;
021import org.springframework.ui.Model;
022import org.springframework.util.Assert;
023import org.springframework.web.bind.support.WebDataBinderFactory;
024import org.springframework.web.context.request.NativeWebRequest;
025import org.springframework.web.method.support.HandlerMethodArgumentResolver;
026import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
027import org.springframework.web.method.support.ModelAndViewContainer;
028
029/**
030 * Resolves {@link Model} arguments and handles {@link Model} return values.
031 *
032 * <p>A {@link Model} return type has a set purpose. Therefore this handler
033 * should be configured ahead of handlers that support any return value type
034 * annotated with {@code @ModelAttribute} or {@code @ResponseBody} to ensure
035 * they don't take over.
036 *
037 * @author Rossen Stoyanchev
038 * @since 3.1
039 */
040public class ModelMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {
041
042        @Override
043        public boolean supportsParameter(MethodParameter parameter) {
044                return Model.class.isAssignableFrom(parameter.getParameterType());
045        }
046
047        @Override
048        @Nullable
049        public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
050                        NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
051
052                Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");
053                return mavContainer.getModel();
054        }
055
056        @Override
057        public boolean supportsReturnType(MethodParameter returnType) {
058                return Model.class.isAssignableFrom(returnType.getParameterType());
059        }
060
061        @Override
062        public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
063                        ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
064
065                if (returnValue == null) {
066                        return;
067                }
068                else if (returnValue instanceof Model) {
069                        mavContainer.addAllAttributes(((Model) returnValue).asMap());
070                }
071                else {
072                        // should not happen
073                        throw new UnsupportedOperationException("Unexpected return type [" +
074                                        returnType.getParameterType().getName() + "] in method: " + returnType.getMethod());
075                }
076        }
077
078}