org.springframework.web.reactive.result.view.ViewResolutionResultHandler Maven / Gradle / Ivy

/*
 * Copyright 2002-2017 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
 *
 *      http://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.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.result.view;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Optional;
import java.util.stream.Collectors;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import org.springframework.beans.BeanUtils;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.core.Conventions;
import org.springframework.core.MethodParameter;
import org.springframework.core.Ordered;
import org.springframework.core.ReactiveAdapter;
import org.springframework.core.ReactiveAdapterRegistry;
import org.springframework.core.ResolvableType;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.ui.Model;
import org.springframework.util.StringUtils;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.support.WebExchangeDataBinder;
import org.springframework.web.reactive.BindingContext;
import org.springframework.web.reactive.HandlerResult;
import org.springframework.web.reactive.HandlerResultHandler;
import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
import org.springframework.web.reactive.result.HandlerResultHandlerSupport;
import org.springframework.web.server.NotAcceptableStatusException;
import org.springframework.web.server.ServerWebExchange;

/**
 * {@code HandlerResultHandler} that encapsulates the view resolution algorithm
 * supporting the following return types:
 * 
 * {@link Void} or no value -- default view name
 * {@link String} -- view name unless {@code @ModelAttribute}-annotated
 * 
{@link View} -- View to render with
 * 
{@link Model} -- attributes to add to the model
 * 
{@link Map} -- attributes to add to the model
 * 
{@link Rendering} -- use case driven API for view resolution
 * {@link ModelAttribute @ModelAttribute} -- attribute for the model
 * 
Non-simple value -- attribute for the model
 * 
 *
 * A String-based view name is resolved through the configured
 * {@link ViewResolver} instances into a {@link View} to use for rendering.
 * If a view is left unspecified (e.g. by returning {@code null} or a
 * model-related return value), a default view name is selected.
 *
 * 
By default this resolver is ordered at {@link Ordered#LOWEST_PRECEDENCE}
 * and generally needs to be late in the order since it interprets any String
 * return value as a view name or any non-simple value type as a model attribute
 * while other result handlers may interpret the same otherwise based on the
 * presence of annotations, e.g. for {@code @ResponseBody}.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class ViewResolutionResultHandler extends HandlerResultHandlerSupport
		implements HandlerResultHandler, Ordered {

	private static final Object NO_VALUE = new Object();

	private static final Mono