/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed 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
 *
 *      https://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.
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package org.springframework.web.method.annotation;

import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;
import org.springframework.ui.Model;
import org.springframework.util.Assert;
import org.springframework.web.bind.support.WebDataBinderFactory;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;

Resolves Model arguments and handles Model return values.

A Model return type has a set purpose. Therefore this handler should be configured ahead of handlers that support any return value type annotated with @ModelAttribute or @ResponseBody to ensure they don't take over.

Author:Rossen Stoyanchev
Since:3.1
/** * Resolves {@link Model} arguments and handles {@link Model} return values. * * <p>A {@link Model} return type has a set purpose. Therefore this handler * should be configured ahead of handlers that support any return value type * annotated with {@code @ModelAttribute} or {@code @ResponseBody} to ensure * they don't take over. * * @author Rossen Stoyanchev * @since 3.1 */
public class ModelMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler { @Override public boolean supportsParameter(MethodParameter parameter) { return Model.class.isAssignableFrom(parameter.getParameterType()); } @Override @Nullable public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer, NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception { Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure"); return mavContainer.getModel(); } @Override public boolean supportsReturnType(MethodParameter returnType) { return Model.class.isAssignableFrom(returnType.getParameterType()); } @Override public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { if (returnValue == null) { return; } else if (returnValue instanceof Model) { mavContainer.addAllAttributes(((Model) returnValue).asMap()); } else { // should not happen throw new UnsupportedOperationException("Unexpected return type [" + returnType.getParameterType().getName() + "] in method: " + returnType.getMethod()); } } }