1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.http.impl.client.cache;
28
29 import java.util.Map;
30
31 import org.apache.http.Header;
32 import org.apache.http.HeaderElement;
33 import org.apache.http.ProtocolException;
34 import org.apache.http.annotation.Contract;
35 import org.apache.http.annotation.ThreadingBehavior;
36 import org.apache.http.client.cache.HeaderConstants;
37 import org.apache.http.client.cache.HttpCacheEntry;
38 import org.apache.http.client.methods.HttpRequestWrapper;
39
40 /**
41 * @since 4.1
42 */
43 @Contract(threading = ThreadingBehavior.IMMUTABLE)
44 class ConditionalRequestBuilder {
45
46 /**
47 * When a {@link HttpCacheEntry} is stale but 'might' be used as a response
48 * to an {@link org.apache.http.HttpRequest} we will attempt to revalidate
49 * the entry with the origin. Build the origin {@link org.apache.http.HttpRequest}
50 * here and return it.
51 *
52 * @param request the original request from the caller
53 * @param cacheEntry the entry that needs to be re-validated
54 * @return the wrapped request
55 * @throws ProtocolException when I am unable to build a new origin request.
56 */
57 public HttpRequestWrapper buildConditionalRequest(final HttpRequestWrapper request, final HttpCacheEntry cacheEntry)
58 throws ProtocolException {
59 final HttpRequestWrapper newRequest = HttpRequestWrapper.wrap(request.getOriginal());
60 newRequest.setHeaders(request.getAllHeaders());
61 final Header eTag = cacheEntry.getFirstHeader(HeaderConstants.ETAG);
62 if (eTag != null) {
63 newRequest.setHeader(HeaderConstants.IF_NONE_MATCH, eTag.getValue());
64 }
65 final Header lastModified = cacheEntry.getFirstHeader(HeaderConstants.LAST_MODIFIED);
66 if (lastModified != null) {
67 newRequest.setHeader(HeaderConstants.IF_MODIFIED_SINCE, lastModified.getValue());
68 }
69 boolean mustRevalidate = false;
70 for(final Header h : cacheEntry.getHeaders(HeaderConstants.CACHE_CONTROL)) {
71 for(final HeaderElement elt : h.getElements()) {
72 if (HeaderConstants.CACHE_CONTROL_MUST_REVALIDATE.equalsIgnoreCase(elt.getName())
73 || HeaderConstants.CACHE_CONTROL_PROXY_REVALIDATE.equalsIgnoreCase(elt.getName())) {
74 mustRevalidate = true;
75 break;
76 }
77 }
78 }
79 if (mustRevalidate) {
80 newRequest.addHeader(HeaderConstants.CACHE_CONTROL, HeaderConstants.CACHE_CONTROL_MAX_AGE + "=0");
81 }
82 return newRequest;
83
84 }
85
86 /**
87 * When a {@link HttpCacheEntry} does not exist for a specific
88 * {@link org.apache.http.HttpRequest} we attempt to see if an existing
89 * {@link HttpCacheEntry} is appropriate by building a conditional
90 * {@link org.apache.http.HttpRequest} using the variants' ETag values.
91 * If no such values exist, the request is unmodified
92 *
93 * @param request the original request from the caller
94 * @param variants
95 * @return the wrapped request
96 */
97 public HttpRequestWrapper buildConditionalRequestFromVariants(final HttpRequestWrapper request,
98 final Map<String, Variant> variants) {
99 final HttpRequestWrapper newRequest = HttpRequestWrapper.wrap(request.getOriginal());
100 newRequest.setHeaders(request.getAllHeaders());
101
102 // we do not support partial content so all etags are used
103 final StringBuilder etags = new StringBuilder();
104 boolean first = true;
105 for(final String etag : variants.keySet()) {
106 if (!first) {
107 etags.append(",");
108 }
109 first = false;
110 etags.append(etag);
111 }
112
113 newRequest.setHeader(HeaderConstants.IF_NONE_MATCH, etags.toString());
114 return newRequest;
115 }
116
117 /**
118 * Returns a request to unconditionally validate a cache entry with
119 * the origin. In certain cases (due to multiple intervening caches)
120 * our cache may actually receive a response to a normal conditional
121 * validation where the Date header is actually older than that of
122 * our current cache entry. In this case, the protocol recommendation
123 * is to retry the validation and force syncup with the origin.
124 * @param request client request we are trying to satisfy
125 * @param entry existing cache entry we are trying to validate
126 * @return an unconditional validation request
127 */
128 public HttpRequestWrapper buildUnconditionalRequest(final HttpRequestWrapper request, final HttpCacheEntry entry) {
129 final HttpRequestWrapper newRequest = HttpRequestWrapper.wrap(request.getOriginal());
130 newRequest.setHeaders(request.getAllHeaders());
131 newRequest.addHeader(HeaderConstants.CACHE_CONTROL,HeaderConstants.CACHE_CONTROL_NO_CACHE);
132 newRequest.addHeader(HeaderConstants.PRAGMA,HeaderConstants.CACHE_CONTROL_NO_CACHE);
133 newRequest.removeHeaders(HeaderConstants.IF_RANGE);
134 newRequest.removeHeaders(HeaderConstants.IF_MATCH);
135 newRequest.removeHeaders(HeaderConstants.IF_NONE_MATCH);
136 newRequest.removeHeaders(HeaderConstants.IF_UNMODIFIED_SINCE);
137 newRequest.removeHeaders(HeaderConstants.IF_MODIFIED_SINCE);
138 return newRequest;
139 }
140
141 }