org.springframework.web.accept.ContentNegotiationManager Maven / Gradle / Ivy
/*
* 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.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.accept;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.web.HttpMediaTypeNotAcceptableException;
import org.springframework.web.context.request.NativeWebRequest;
/**
* Central class to determine requested {@linkplain MediaType media types}
* for a request. This is done by delegating to a list of configured
* {@code ContentNegotiationStrategy} instances.
*
* Also provides methods to look up file extensions for a media type.
* This is done by delegating to the list of configured
* {@code MediaTypeFileExtensionResolver} instances.
*
* @author Rossen Stoyanchev
* @author Juergen Hoeller
* @since 3.2
*/
public class ContentNegotiationManager implements ContentNegotiationStrategy, MediaTypeFileExtensionResolver {
private final List strategies = new ArrayList<>();
private final Set resolvers = new LinkedHashSet<>();
/**
* Create an instance with the given list of
* {@code ContentNegotiationStrategy} strategies each of which may also be
* an instance of {@code MediaTypeFileExtensionResolver}.
* @param strategies the strategies to use
*/
public ContentNegotiationManager(ContentNegotiationStrategy... strategies) {
this(Arrays.asList(strategies));
}
/**
* A collection-based alternative to
* {@link #ContentNegotiationManager(ContentNegotiationStrategy...)}.
* @param strategies the strategies to use
* @since 3.2.2
*/
public ContentNegotiationManager(Collection strategies) {
Assert.notEmpty(strategies, "At least one ContentNegotiationStrategy is expected");
this.strategies.addAll(strategies);
for (ContentNegotiationStrategy strategy : this.strategies) {
if (strategy instanceof MediaTypeFileExtensionResolver) {
this.resolvers.add((MediaTypeFileExtensionResolver) strategy);
}
}
}
/**
* Create a default instance with a {@link HeaderContentNegotiationStrategy}.
*/
public ContentNegotiationManager() {
this(new HeaderContentNegotiationStrategy());
}
/**
* Return the configured content negotiation strategies.
* @since 3.2.16
*/
public List getStrategies() {
return this.strategies;
}
/**
* Find a {@code ContentNegotiationStrategy} of the given type.
* @param strategyType the strategy type
* @return the first matching strategy, or {@code null} if none
* @since 4.3
*/
@SuppressWarnings("unchecked")
@Nullable
public T getStrategy(Class strategyType) {
for (ContentNegotiationStrategy strategy : getStrategies()) {
if (strategyType.isInstance(strategy)) {
return (T) strategy;
}
}
return null;
}
/**
* Register more {@code MediaTypeFileExtensionResolver} instances in addition
* to those detected at construction.
* @param resolvers the resolvers to add
*/
public void addFileExtensionResolvers(MediaTypeFileExtensionResolver... resolvers) {
Collections.addAll(this.resolvers, resolvers);
}
@Override
public List resolveMediaTypes(NativeWebRequest request) throws HttpMediaTypeNotAcceptableException {
for (ContentNegotiationStrategy strategy : this.strategies) {
List mediaTypes = strategy.resolveMediaTypes(request);
if (mediaTypes.equals(MEDIA_TYPE_ALL_LIST)) {
continue;
}
return mediaTypes;
}
return MEDIA_TYPE_ALL_LIST;
}
@Override
public List resolveFileExtensions(MediaType mediaType) {
return doResolveExtensions(resolver -> resolver.resolveFileExtensions(mediaType));
}
/**
* {@inheritDoc}
* At startup this method returns extensions explicitly registered with
* either {@link PathExtensionContentNegotiationStrategy} or
* {@link ParameterContentNegotiationStrategy}. At runtime if there is a
* "path extension" strategy and its
* {@link PathExtensionContentNegotiationStrategy#setUseRegisteredExtensionsOnly(boolean)
* useRegisteredExtensionsOnly} property is set to "false", the list of extensions may
* increase as file extensions are resolved via
* {@link org.springframework.http.MediaTypeFactory} and cached.
*/
@Override
public List getAllFileExtensions() {
return doResolveExtensions(MediaTypeFileExtensionResolver::getAllFileExtensions);
}
private List doResolveExtensions(Function> extractor) {
List result = null;
for (MediaTypeFileExtensionResolver resolver : this.resolvers) {
List extensions = extractor.apply(resolver);
if (CollectionUtils.isEmpty(extensions)) {
continue;
}
result = (result != null ? result : new ArrayList<>(4));
for (String extension : extensions) {
if (!result.contains(extension)) {
result.add(extension);
}
}
}
return (result != null ? result : Collections.emptyList());
}
/**
* Return all registered lookup key to media type mappings by iterating
* {@link MediaTypeFileExtensionResolver}s.
* @since 5.2.4
*/
public Map getMediaTypeMappings() {
Map result = null;
for (MediaTypeFileExtensionResolver resolver : this.resolvers) {
if (resolver instanceof MappingMediaTypeFileExtensionResolver) {
Map map = ((MappingMediaTypeFileExtensionResolver) resolver).getMediaTypes();
if (CollectionUtils.isEmpty(map)) {
continue;
}
result = (result != null ? result : new HashMap<>(4));
result.putAll(map);
}
}
return (result != null ? result : Collections.emptyMap());
}
}