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