001/*
002 * Copyright 2002-2018 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 java.util.Collections;
020
021import reactor.core.publisher.Mono;
022
023import org.springframework.core.io.Resource;
024import org.springframework.lang.Nullable;
025import org.springframework.util.StringUtils;
026import org.springframework.web.server.ServerWebExchange;
027
028/**
029 * A base class for a {@code ResourceTransformer} with an optional helper method
030 * for resolving public links within a transformed resource.
031 *
032 * @author Rossen Stoyanchev
033 * @author Brian Clozel
034 * @since 5.0
035 */
036public abstract class ResourceTransformerSupport implements ResourceTransformer {
037
038        @Nullable
039        private ResourceUrlProvider resourceUrlProvider;
040
041
042        /**
043         * Configure a {@link ResourceUrlProvider} to use when resolving the public
044         * URL of links in a transformed resource (e.g. import links in a CSS file).
045         * This is required only for links expressed as full paths and not for
046         * relative links.
047         * @param resourceUrlProvider the URL provider to use
048         */
049        public void setResourceUrlProvider(@Nullable ResourceUrlProvider resourceUrlProvider) {
050                this.resourceUrlProvider = resourceUrlProvider;
051        }
052
053        /**
054         * Return the configured {@code ResourceUrlProvider}.
055         */
056        @Nullable
057        public ResourceUrlProvider getResourceUrlProvider() {
058                return this.resourceUrlProvider;
059        }
060
061
062        /**
063         * A transformer can use this method when a resource being transformed
064         * contains links to other resources. Such links need to be replaced with the
065         * public facing link as determined by the resource resolver chain (e.g. the
066         * public URL may have a version inserted).
067         * @param resourcePath the path to a resource that needs to be re-written
068         * @param exchange the current exchange
069         * @param resource the resource being transformed
070         * @param transformerChain the transformer chain
071         * @return the resolved URL or an empty {@link Mono}
072         */
073        protected Mono<String> resolveUrlPath(String resourcePath, ServerWebExchange exchange,
074                        Resource resource, ResourceTransformerChain transformerChain) {
075
076                if (resourcePath.startsWith("/")) {
077                        // full resource path
078                        ResourceUrlProvider urlProvider = getResourceUrlProvider();
079                        return (urlProvider != null ? urlProvider.getForUriString(resourcePath, exchange) : Mono.empty());
080                }
081                else {
082                        // try resolving as relative path
083                        return transformerChain.getResolverChain()
084                                        .resolveUrlPath(resourcePath, Collections.singletonList(resource));
085                }
086        }
087
088        /**
089         * Transform the given relative request path to an absolute path,
090         * taking the path of the given request as a point of reference.
091         * The resulting path is also cleaned from sequences like "path/..".
092         *
093         * @param path the relative path to transform
094         * @param exchange the current exchange
095         * @return the absolute request path for the given resource path
096         */
097        protected String toAbsolutePath(String path, ServerWebExchange exchange) {
098                String requestPath = exchange.getRequest().getURI().getPath();
099                String absolutePath = (path.startsWith("/") ? path : StringUtils.applyRelativePath(requestPath, path));
100                return StringUtils.cleanPath(absolutePath);
101        }
102
103}