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.servlet.resource; 018 019import java.io.IOException; 020 021import javax.servlet.http.HttpServletRequest; 022 023import org.apache.commons.logging.Log; 024import org.apache.commons.logging.LogFactory; 025 026import org.springframework.cache.Cache; 027import org.springframework.cache.CacheManager; 028import org.springframework.core.io.Resource; 029import org.springframework.util.Assert; 030 031/** 032 * A {@link org.springframework.web.servlet.resource.ResourceTransformer} that checks a 033 * {@link org.springframework.cache.Cache} to see if a previously transformed resource 034 * exists in the cache and returns it if found, and otherwise delegates to the resolver 035 * chain and saves the result in the cache. 036 * 037 * @author Rossen Stoyanchev 038 * @since 4.1 039 */ 040public class CachingResourceTransformer implements ResourceTransformer { 041 042 private static final Log logger = LogFactory.getLog(CachingResourceTransformer.class); 043 044 private final Cache cache; 045 046 047 public CachingResourceTransformer(Cache cache) { 048 Assert.notNull(cache, "Cache is required"); 049 this.cache = cache; 050 } 051 052 public CachingResourceTransformer(CacheManager cacheManager, String cacheName) { 053 Cache cache = cacheManager.getCache(cacheName); 054 if (cache == null) { 055 throw new IllegalArgumentException("Cache '" + cacheName + "' not found"); 056 } 057 this.cache = cache; 058 } 059 060 061 /** 062 * Return the configured {@code Cache}. 063 */ 064 public Cache getCache() { 065 return this.cache; 066 } 067 068 069 @Override 070 public Resource transform(HttpServletRequest request, Resource resource, ResourceTransformerChain transformerChain) 071 throws IOException { 072 073 Resource transformed = this.cache.get(resource, Resource.class); 074 if (transformed != null) { 075 logger.trace("Resource resolved from cache"); 076 return transformed; 077 } 078 079 transformed = transformerChain.transform(request, resource); 080 this.cache.put(resource, transformed); 081 082 return transformed; 083 } 084 085}