001/*
002 * Copyright 2002-2016 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.config.annotation;
018
019import java.util.ArrayList;
020import java.util.List;
021
022import org.springframework.cache.Cache;
023import org.springframework.cache.concurrent.ConcurrentMapCache;
024import org.springframework.util.Assert;
025import org.springframework.util.ClassUtils;
026import org.springframework.web.servlet.resource.CachingResourceResolver;
027import org.springframework.web.servlet.resource.CachingResourceTransformer;
028import org.springframework.web.servlet.resource.CssLinkResourceTransformer;
029import org.springframework.web.servlet.resource.PathResourceResolver;
030import org.springframework.web.servlet.resource.ResourceResolver;
031import org.springframework.web.servlet.resource.ResourceTransformer;
032import org.springframework.web.servlet.resource.VersionResourceResolver;
033import org.springframework.web.servlet.resource.WebJarsResourceResolver;
034
035/**
036 * Assists with the registration of resource resolvers and transformers.
037 *
038 * @author Rossen Stoyanchev
039 * @since 4.1
040 */
041public class ResourceChainRegistration {
042
043        private static final String DEFAULT_CACHE_NAME = "spring-resource-chain-cache";
044
045        private static final boolean isWebJarsAssetLocatorPresent = ClassUtils.isPresent(
046                        "org.webjars.WebJarAssetLocator", ResourceChainRegistration.class.getClassLoader());
047
048
049        private final List<ResourceResolver> resolvers = new ArrayList<ResourceResolver>(4);
050
051        private final List<ResourceTransformer> transformers = new ArrayList<ResourceTransformer>(4);
052
053        private boolean hasVersionResolver;
054
055        private boolean hasPathResolver;
056
057        private boolean hasCssLinkTransformer;
058
059        private boolean hasWebjarsResolver;
060
061
062        public ResourceChainRegistration(boolean cacheResources) {
063                this(cacheResources, cacheResources ? new ConcurrentMapCache(DEFAULT_CACHE_NAME) : null);
064        }
065
066        public ResourceChainRegistration(boolean cacheResources, Cache cache) {
067                Assert.isTrue(!cacheResources || cache != null, "'cache' is required when cacheResources=true");
068                if (cacheResources) {
069                        this.resolvers.add(new CachingResourceResolver(cache));
070                        this.transformers.add(new CachingResourceTransformer(cache));
071                }
072        }
073
074
075        /**
076         * Add a resource resolver to the chain.
077         * @param resolver the resolver to add
078         * @return the current instance for chained method invocation
079         */
080        public ResourceChainRegistration addResolver(ResourceResolver resolver) {
081                Assert.notNull(resolver, "The provided ResourceResolver should not be null");
082                this.resolvers.add(resolver);
083                if (resolver instanceof VersionResourceResolver) {
084                        this.hasVersionResolver = true;
085                }
086                else if (resolver instanceof PathResourceResolver) {
087                        this.hasPathResolver = true;
088                }
089                else if (resolver instanceof WebJarsResourceResolver) {
090                        this.hasWebjarsResolver = true;
091                }
092                return this;
093        }
094
095        /**
096         * Add a resource transformer to the chain.
097         * @param transformer the transformer to add
098         * @return the current instance for chained method invocation
099         */
100        public ResourceChainRegistration addTransformer(ResourceTransformer transformer) {
101                Assert.notNull(transformer, "The provided ResourceTransformer should not be null");
102                this.transformers.add(transformer);
103                if (transformer instanceof CssLinkResourceTransformer) {
104                        this.hasCssLinkTransformer = true;
105                }
106                return this;
107        }
108
109        protected List<ResourceResolver> getResourceResolvers() {
110                if (!this.hasPathResolver) {
111                        List<ResourceResolver> result = new ArrayList<ResourceResolver>(this.resolvers);
112                        if (isWebJarsAssetLocatorPresent && !this.hasWebjarsResolver) {
113                                result.add(new WebJarsResourceResolver());
114                        }
115                        result.add(new PathResourceResolver());
116                        return result;
117                }
118                return this.resolvers;
119        }
120
121        protected List<ResourceTransformer> getResourceTransformers() {
122                if (this.hasVersionResolver && !this.hasCssLinkTransformer) {
123                        List<ResourceTransformer> result = new ArrayList<ResourceTransformer>(this.transformers);
124                        boolean hasTransformers = !this.transformers.isEmpty();
125                        boolean hasCaching = hasTransformers && this.transformers.get(0) instanceof CachingResourceTransformer;
126                        result.add(hasCaching ? 1 : 0, new CssLinkResourceTransformer());
127                        return result;
128                }
129                return this.transformers;
130        }
131
132}