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.hc.client5.http.impl.cache;
28
29 import java.util.Iterator;
30 import java.util.Map;
31
32 import org.apache.hc.client5.http.cache.HeaderConstants;
33 import org.apache.hc.client5.http.cache.HttpCacheEntry;
34 import org.apache.hc.core5.function.Factory;
35 import org.apache.hc.core5.http.Header;
36 import org.apache.hc.core5.http.HeaderElement;
37 import org.apache.hc.core5.http.HttpRequest;
38 import org.apache.hc.core5.http.message.MessageSupport;
39
40 class ConditionalRequestBuilder<T extends HttpRequest> {
41
42 private final Factory<T, T> messageCopier;
43
44 ConditionalRequestBuilder(final Factory<T, T> messageCopier) {
45 this.messageCopier = messageCopier;
46 }
47
48 /**
49 * When a {@link HttpCacheEntry} is stale but 'might' be used as a response
50 * to an {@link org.apache.hc.core5.http.HttpRequest} we will attempt to revalidate
51 * the entry with the origin. Build the origin {@link org.apache.hc.core5.http.HttpRequest}
52 * here and return it.
53 *
54 * @param request the original request from the caller
55 * @param cacheEntry the entry that needs to be re-validated
56 * @return the wrapped request
57 */
58 public T buildConditionalRequest(final T request, final HttpCacheEntry cacheEntry) {
59 final T newRequest = messageCopier.create(request);
60
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 final Iterator<HeaderElement> it = MessageSupport.iterate(cacheEntry, HeaderConstants.CACHE_CONTROL);
71 while (it.hasNext()) {
72 final HeaderElement elt = it.next();
73 if (HeaderConstants.CACHE_CONTROL_MUST_REVALIDATE.equalsIgnoreCase(elt.getName())
74 || HeaderConstants.CACHE_CONTROL_PROXY_REVALIDATE.equalsIgnoreCase(elt.getName())) {
75 mustRevalidate = true;
76 break;
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.hc.core5.http.HttpRequest} we attempt to see if an existing
89 * {@link HttpCacheEntry} is appropriate by building a conditional
90 * {@link org.apache.hc.core5.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 T buildConditionalRequestFromVariants(final T request, final Map<String, Variant> variants) {
98 final T newRequest = messageCopier.create(request);
99
100 // we do not support partial content so all etags are used
101 final StringBuilder etags = new StringBuilder();
102 boolean first = true;
103 for(final String etag : variants.keySet()) {
104 if (!first) {
105 etags.append(",");
106 }
107 first = false;
108 etags.append(etag);
109 }
110
111 newRequest.setHeader(HeaderConstants.IF_NONE_MATCH, etags.toString());
112 return newRequest;
113 }
114
115 /**
116 * Returns a request to unconditionally validate a cache entry with
117 * the origin. In certain cases (due to multiple intervening caches)
118 * our cache may actually receive a response to a normal conditional
119 * validation where the Date header is actually older than that of
120 * our current cache entry. In this case, the protocol recommendation
121 * is to retry the validation and force syncup with the origin.
122 * @param request client request we are trying to satisfy
123 * @return an unconditional validation request
124 */
125 public T buildUnconditionalRequest(final T request) {
126 final T newRequest = messageCopier.create(request);
127 newRequest.addHeader(HeaderConstants.CACHE_CONTROL,HeaderConstants.CACHE_CONTROL_NO_CACHE);
128 newRequest.addHeader(HeaderConstants.PRAGMA,HeaderConstants.CACHE_CONTROL_NO_CACHE);
129 newRequest.removeHeaders(HeaderConstants.IF_RANGE);
130 newRequest.removeHeaders(HeaderConstants.IF_MATCH);
131 newRequest.removeHeaders(HeaderConstants.IF_NONE_MATCH);
132 newRequest.removeHeaders(HeaderConstants.IF_UNMODIFIED_SINCE);
133 newRequest.removeHeaders(HeaderConstants.IF_MODIFIED_SINCE);
134 return newRequest;
135 }
136
137 }