/*
* Copyright 2002-2015 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.servlet.resource;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import org.springframework.cache.Cache;
import org.springframework.cache.CacheManager;
import org.springframework.core.io.Resource;
import org.springframework.util.Assert;
/**
* A {@link org.springframework.web.servlet.resource.ResourceResolver} that
* resolves resources from a {@link org.springframework.cache.Cache} or otherwise
* delegates to the resolver chain and saves the result in the cache.
*
* @author Rossen Stoyanchev
* @author Brian Clozel
* @since 4.1
*/
public class CachingResourceResolver extends AbstractResourceResolver {
public static final String RESOLVED_RESOURCE_CACHE_KEY_PREFIX = "resolvedResource:";
public static final String RESOLVED_URL_PATH_CACHE_KEY_PREFIX = "resolvedUrlPath:";
private final Cache cache;
public CachingResourceResolver(CacheManager cacheManager, String cacheName) {
this(cacheManager.getCache(cacheName));
}
public CachingResourceResolver(Cache cache) {
Assert.notNull(cache, "Cache is required");
this.cache = cache;
}
/**
* Return the configured {@code Cache}.
*/
public Cache getCache() {
return this.cache;
}
@Override
protected Resource resolveResourceInternal(HttpServletRequest request, String requestPath,
List<? extends Resource> locations, ResourceResolverChain chain) {
String key = computeKey(request, requestPath);
Resource resource = this.cache.get(key, Resource.class);
if (resource != null) {
if (logger.isTraceEnabled()) {
logger.trace("Found match: " + resource);
}
return resource;
}
resource = chain.resolveResource(request, requestPath, locations);
if (resource != null) {
if (logger.isTraceEnabled()) {
logger.trace("Putting resolved resource in cache: " + resource);
}
this.cache.put(key, resource);
}
return resource;
}
protected String computeKey(HttpServletRequest request, String requestPath) {
StringBuilder key = new StringBuilder(RESOLVED_RESOURCE_CACHE_KEY_PREFIX);
key.append(requestPath);
if (request != null) {
String encoding = request.getHeader("Accept-Encoding");
if (encoding != null && encoding.contains("gzip")) {
key.append("+encoding=gzip");
}
}
return key.toString();
}
@Override
protected String resolveUrlPathInternal(String resourceUrlPath,
List<? extends Resource> locations, ResourceResolverChain chain) {
String key = RESOLVED_URL_PATH_CACHE_KEY_PREFIX + resourceUrlPath;
String resolvedUrlPath = this.cache.get(key, String.class);
if (resolvedUrlPath != null) {
if (logger.isTraceEnabled()) {
logger.trace("Found match: \"" + resolvedUrlPath + "\"");
}
return resolvedUrlPath;
}
resolvedUrlPath = chain.resolveUrlPath(resourceUrlPath, locations);
if (resolvedUrlPath != null) {
if (logger.isTraceEnabled()) {
logger.trace("Putting resolved resource URL path in cache: \"" + resolvedUrlPath + "\"");
}
this.cache.put(key, resolvedUrlPath);
}
return resolvedUrlPath;
}
}