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.reactive.resource;
018
019import org.apache.commons.logging.Log;
020import org.apache.commons.logging.LogFactory;
021import reactor.core.publisher.Mono;
022
023import org.springframework.cache.Cache;
024import org.springframework.cache.CacheManager;
025import org.springframework.core.io.Resource;
026import org.springframework.util.Assert;
027import org.springframework.web.server.ServerWebExchange;
028
029/**
030 * A {@link ResourceTransformer} that checks a {@link Cache} to see if a
031 * previously transformed resource exists in the cache and returns it if found,
032 * or otherwise delegates to the resolver chain and caches the result.
033 *
034 * @author Rossen Stoyanchev
035 * @since 5.0
036 */
037public class CachingResourceTransformer implements ResourceTransformer {
038
039        private static final Log logger = LogFactory.getLog(CachingResourceTransformer.class);
040
041        private final Cache cache;
042
043
044        public CachingResourceTransformer(Cache cache) {
045                Assert.notNull(cache, "Cache is required");
046                this.cache = cache;
047        }
048
049        public CachingResourceTransformer(CacheManager cacheManager, String cacheName) {
050                Cache cache = cacheManager.getCache(cacheName);
051                if (cache == null) {
052                        throw new IllegalArgumentException("Cache '" + cacheName + "' not found");
053                }
054                this.cache = cache;
055        }
056
057
058        /**
059         * Return the configured {@code Cache}.
060         */
061        public Cache getCache() {
062                return this.cache;
063        }
064
065
066        @Override
067        public Mono<Resource> transform(ServerWebExchange exchange, Resource resource,
068                        ResourceTransformerChain transformerChain) {
069
070                Resource cachedResource = this.cache.get(resource, Resource.class);
071                if (cachedResource != null) {
072                        if (logger.isTraceEnabled()) {
073                                logger.trace(exchange.getLogPrefix() + "Resource resolved from cache");
074                        }
075                        return Mono.just(cachedResource);
076                }
077
078                return transformerChain.transform(exchange, resource)
079                                .doOnNext(transformed -> this.cache.put(resource, transformed));
080        }
081
082}