001/*
002 * Copyright 2002-2019 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.mvc.method.annotation;
018
019import org.springframework.core.MethodParameter;
020import org.springframework.web.context.request.NativeWebRequest;
021import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
022import org.springframework.web.method.support.ModelAndViewContainer;
023import org.springframework.web.servlet.RequestToViewNameTranslator;
024import org.springframework.web.servlet.SmartView;
025import org.springframework.web.servlet.View;
026
027/**
028 * Handles return values that are of type {@link View}.
029 *
030 * <p>A {@code null} return value is left as-is leaving it to the configured
031 * {@link RequestToViewNameTranslator} to select a view name by convention.
032 *
033 * <p>A {@link View} return type has a set purpose. Therefore this handler
034 * should be configured ahead of handlers that support any return value type
035 * annotated with {@code @ModelAttribute} or {@code @ResponseBody} to ensure
036 * they don't take over.
037 *
038 * @author Rossen Stoyanchev
039 * @since 3.1
040 */
041public class ViewMethodReturnValueHandler implements HandlerMethodReturnValueHandler {
042
043        @Override
044        public boolean supportsReturnType(MethodParameter returnType) {
045                return View.class.isAssignableFrom(returnType.getParameterType());
046        }
047
048        @Override
049        public void handleReturnValue(Object returnValue, MethodParameter returnType,
050                        ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
051
052                if (returnValue == null) {
053                        return;
054                }
055                else if (returnValue instanceof View) {
056                        View view = (View) returnValue;
057                        mavContainer.setView(view);
058                        if (view instanceof SmartView) {
059                                if (((SmartView) view).isRedirectView()) {
060                                        mavContainer.setRedirectModelScenario(true);
061                                }
062                        }
063                }
064                else {
065                        // should not happen
066                        throw new UnsupportedOperationException("Unexpected return type: " +
067                                        returnType.getParameterType().getName() + " in method: " + returnType.getMethod());
068                }
069        }
070
071}