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.servlet.resource; 018 019import java.util.Collections; 020 021import javax.servlet.http.HttpServletRequest; 022 023import org.springframework.core.io.Resource; 024import org.springframework.lang.Nullable; 025import org.springframework.util.Assert; 026import org.springframework.util.StringUtils; 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 Brian Clozel 033 * @author Rossen Stoyanchev 034 * @author Juergen Hoeller 035 * @since 4.1 036 */ 037public abstract class ResourceTransformerSupport implements ResourceTransformer { 038 039 @Nullable 040 private ResourceUrlProvider resourceUrlProvider; 041 042 043 /** 044 * Configure a {@link ResourceUrlProvider} to use when resolving the public 045 * URL of links in a transformed resource (e.g. import links in a CSS file). 046 * This is required only for links expressed as full paths and not for 047 * relative links. 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 request the current request 069 * @param resource the resource being transformed 070 * @param transformerChain the transformer chain 071 * @return the resolved URL, or {@code} if not resolvable 072 */ 073 @Nullable 074 protected String resolveUrlPath(String resourcePath, HttpServletRequest request, 075 Resource resource, ResourceTransformerChain transformerChain) { 076 077 if (resourcePath.startsWith("/")) { 078 // full resource path 079 ResourceUrlProvider urlProvider = findResourceUrlProvider(request); 080 return (urlProvider != null ? urlProvider.getForRequestUrl(request, resourcePath) : null); 081 } 082 else { 083 // try resolving as relative path 084 return transformerChain.getResolverChain().resolveUrlPath( 085 resourcePath, Collections.singletonList(resource)); 086 } 087 } 088 089 /** 090 * Transform the given relative request path to an absolute path, 091 * taking the path of the given request as a point of reference. 092 * The resulting path is also cleaned from sequences like "path/..". 093 * @param path the relative path to transform 094 * @param request the referer request 095 * @return the absolute request path for the given resource path 096 */ 097 protected String toAbsolutePath(String path, HttpServletRequest request) { 098 String absolutePath = path; 099 if (!path.startsWith("/")) { 100 ResourceUrlProvider urlProvider = findResourceUrlProvider(request); 101 Assert.state(urlProvider != null, "No ResourceUrlProvider"); 102 String requestPath = urlProvider.getUrlPathHelper().getRequestUri(request); 103 absolutePath = StringUtils.applyRelativePath(requestPath, path); 104 } 105 return StringUtils.cleanPath(absolutePath); 106 } 107 108 @Nullable 109 private ResourceUrlProvider findResourceUrlProvider(HttpServletRequest request) { 110 if (this.resourceUrlProvider != null) { 111 return this.resourceUrlProvider; 112 } 113 return (ResourceUrlProvider) request.getAttribute( 114 ResourceUrlProviderExposingInterceptor.RESOURCE_URL_PROVIDER_ATTR); 115 } 116 117}