1 /*
2 * Copyright 2002-2014 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package org.springframework.web.servlet.resource;
17
18 import java.util.Arrays;
19 import javax.servlet.http.HttpServletRequest;
20
21 import org.springframework.core.io.Resource;
22
23 /**
24 * A base class for a {@code ResourceTransformer} with an optional helper method
25 * for resolving public links within a transformed resource.
26 *
27 * @author Brian Clozel
28 * @author Rossen Stoyanchev
29 * @since 4.1
30 */
31 public abstract class ResourceTransformerSupport implements ResourceTransformer {
32
33 private ResourceUrlProvider resourceUrlProvider;
34
35
36 /**
37 * Configure a {@link ResourceUrlProvider} to use when resolving the public
38 * URL of links in a transformed resource (e.g. import links in a CSS file).
39 * This is required only for links expressed as full paths, i.e. including
40 * context and servlet path, and not for relative links.
41 *
42 * <p>By default this property is not set. In that case if a
43 * {@code ResourceUrlProvider} is needed an attempt is made to find the
44 * {@code ResourceUrlProvider} exposed through the
45 * {@link org.springframework.web.servlet.resource.ResourceUrlProviderExposingInterceptor
46 * ResourceUrlProviderExposingInterceptor} (configured by default in the MVC
47 * Java config and XML namespace). Therefore explicitly configuring this
48 * property should not be needed in most cases.
49 * @param resourceUrlProvider the URL provider to use
50 */
51 public void setResourceUrlProvider(ResourceUrlProvider resourceUrlProvider) {
52 this.resourceUrlProvider = resourceUrlProvider;
53 }
54
55 /**
56 * @return the configured {@code ResourceUrlProvider}.
57 */
58 public ResourceUrlProvider getResourceUrlProvider() {
59 return this.resourceUrlProvider;
60 }
61
62
63 /**
64 * A transformer can use this method when a resource being transformed
65 * contains links to other resources. Such links need to be replaced with the
66 * public facing link as determined by the resource resolver chain (e.g. the
67 * public URL may have a version inserted).
68 *
69 * @param resourcePath the path to a resource that needs to be re-written
70 * @param request the current request
71 * @param resource the resource being transformed
72 * @param transformerChain the transformer chain
73 * @return the resolved URL or null
74 */
75 protected String resolveUrlPath(String resourcePath, HttpServletRequest request,
76 Resource resource, ResourceTransformerChain transformerChain) {
77
78 if (resourcePath.startsWith("/")) {
79 // full resource path
80 ResourceUrlProvider urlProvider = findResourceUrlProvider(request);
81 return (urlProvider != null ? urlProvider.getForRequestUrl(request, resourcePath) : null);
82 }
83 else {
84 // try resolving as relative path
85 return transformerChain.getResolverChain().resolveUrlPath(resourcePath, Arrays.asList(resource));
86 }
87 }
88
89 private ResourceUrlProvider findResourceUrlProvider(HttpServletRequest request) {
90 if (this.resourceUrlProvider != null) {
91 return this.resourceUrlProvider;
92 }
93 return (ResourceUrlProvider) request.getAttribute(
94 ResourceUrlProviderExposingInterceptor.RESOURCE_URL_PROVIDER_ATTR);
95 }
96
97 }