/*
* Copyright 2002-2016 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.accept;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.springframework.http.MediaType;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;
import org.springframework.web.server.NotAcceptableStatusException;
import org.springframework.web.server.ServerWebExchange;
/**
* Abstract base class for {@link MappingContentTypeResolver} implementations.
* Maintains the actual mappings and pre-implements the overall algorithm with
* sub-classes left to provide a way to extract the lookup key (e.g. file
* extension, query parameter, etc) for a given exchange.
*
* @author Rossen Stoyanchev
* @since 5.0
*/
public abstract class AbstractMappingContentTypeResolver implements MappingContentTypeResolver {
/** Primary lookup for media types by key (e.g. "json" -> "application/json") */
private final Map<String, MediaType> mediaTypeLookup = new ConcurrentHashMap<>(64);
/** Reverse lookup for keys associated with a media type */
private final MultiValueMap<MediaType, String> keyLookup = new LinkedMultiValueMap<>(64);
/**
* Create an instance with the given map of file extensions and media types.
*/
public AbstractMappingContentTypeResolver(Map<String, MediaType> mediaTypes) {
if (mediaTypes != null) {
for (Map.Entry<String, MediaType> entry : mediaTypes.entrySet()) {
String extension = entry.getKey().toLowerCase(Locale.ENGLISH);
MediaType mediaType = entry.getValue();
this.mediaTypeLookup.put(extension, mediaType);
this.keyLookup.add(mediaType, extension);
}
}
}
public Map<String, MediaType> getMediaTypes() {
return this.mediaTypeLookup;
}
/**
* Sub-classes can use this method to look up a MediaType by key.
* @param key the key converted to lower case
* @return a MediaType or {@code null}
*/
protected MediaType getMediaType(String key) {
return this.mediaTypeLookup.get(key.toLowerCase(Locale.ENGLISH));
}
/**
* Sub-classes can use this method get all mapped media types.
*/
protected List<MediaType> getAllMediaTypes() {
return new ArrayList<>(this.mediaTypeLookup.values());
}
// RequestedContentTypeResolver implementation
@Override
public List<MediaType> resolveMediaTypes(ServerWebExchange exchange)
throws NotAcceptableStatusException {
String key = extractKey(exchange);
return resolveMediaTypes(key);
}
/**
* An overloaded resolve method with a pre-resolved lookup key.
* @param key the key for looking up media types
* @return a list of resolved media types or an empty list
* @throws NotAcceptableStatusException
*/
public List<MediaType> resolveMediaTypes(String key) throws NotAcceptableStatusException {
if (StringUtils.hasText(key)) {
MediaType mediaType = getMediaType(key);
if (mediaType != null) {
handleMatch(key, mediaType);
return Collections.singletonList(mediaType);
}
mediaType = handleNoMatch(key);
if (mediaType != null) {
MediaType previous = this.mediaTypeLookup.putIfAbsent(key, mediaType);
if (previous == null) {
this.keyLookup.add(mediaType, key);
}
return Collections.singletonList(mediaType);
}
}
return Collections.emptyList();
}
/**
* Extract the key to use to look up a media type from the given exchange,
* e.g. file extension, query parameter, etc.
* @return the key or {@code null}
*/
protected abstract String extractKey(ServerWebExchange exchange);
/**
* Override to provide handling when a key is successfully resolved via
* {@link #getMediaType(String)}.
*/
@SuppressWarnings("UnusedParameters")
protected void handleMatch(String key, MediaType mediaType) {
}
/**
* Override to provide handling when a key is not resolved via.
* {@link #getMediaType(String)}. If a MediaType is returned from
* this method it will be added to the mappings.
*/
@SuppressWarnings("UnusedParameters")
protected MediaType handleNoMatch(String key) throws NotAcceptableStatusException {
return null;
}
// MappingContentTypeResolver implementation
@Override
public Set<String> getKeysFor(MediaType mediaType) {
List<String> keys = this.keyLookup.get(mediaType);
return (keys != null ? new HashSet<>(keys) : Collections.emptySet());
}
@Override
public Set<String> getKeys() {
return new HashSet<>(this.mediaTypeLookup.keySet());
}
}