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.Collection;
30
31 import org.apache.hc.client5.http.cache.HeaderConstants;
32 import org.apache.hc.client5.http.cache.HttpCacheEntry;
33 import org.apache.hc.client5.http.cache.ResponseCacheControl;
34 import org.apache.hc.client5.http.validator.ETag;
35 import org.apache.hc.core5.function.Factory;
36 import org.apache.hc.core5.http.Header;
37 import org.apache.hc.core5.http.HttpHeaders;
38 import org.apache.hc.core5.http.HttpRequest;
39 import org.apache.hc.core5.http.message.BufferedHeader;
40 import org.apache.hc.core5.util.CharArrayBuffer;
41
42 class ConditionalRequestBuilder<T extends HttpRequest> {
43
44 private final Factory<T, T> messageCopier;
45
46 ConditionalRequestBuilder(final Factory<T, T> messageCopier) {
47 this.messageCopier = messageCopier;
48 }
49
50 /**
51 * When a {@link HttpCacheEntry} is stale but 'might' be used as a response
52 * to an {@link org.apache.hc.core5.http.HttpRequest} we will attempt to revalidate
53 * the entry with the origin. Build the origin {@link org.apache.hc.core5.http.HttpRequest}
54 * here and return it.
55 *
56 * @param cacheControl the cache control directives.
57 * @param request the original request from the caller
58 * @param cacheEntry the entry that needs to be re-validated
59 * @return the wrapped request
60 */
61 public T buildConditionalRequest(final ResponseCacheControl cacheControl, final T request, final HttpCacheEntry cacheEntry) {
62 final T newRequest = messageCopier.create(request);
63
64 final ETag eTag = cacheEntry.getETag();
65 if (eTag != null) {
66 newRequest.setHeader(HttpHeaders.IF_NONE_MATCH, eTag.toString());
67 }
68 final Header lastModified = cacheEntry.getFirstHeader(HttpHeaders.LAST_MODIFIED);
69 if (lastModified != null) {
70 newRequest.setHeader(HttpHeaders.IF_MODIFIED_SINCE, lastModified.getValue());
71 }
72 if (cacheControl.isMustRevalidate() || cacheControl.isProxyRevalidate()) {
73 newRequest.addHeader(HttpHeaders.CACHE_CONTROL, HeaderConstants.CACHE_CONTROL_MAX_AGE + "=0");
74 }
75 return newRequest;
76
77 }
78
79 /**
80 * When a {@link HttpCacheEntry} does not exist for a specific
81 * {@link org.apache.hc.core5.http.HttpRequest} we attempt to see if an existing
82 * {@link HttpCacheEntry} is appropriate by building a conditional
83 * {@link org.apache.hc.core5.http.HttpRequest} using the variants' ETag values.
84 * If no such values exist, the request is unmodified
85 *
86 * @param request the original request from the caller
87 * @param variants
88 * @return the wrapped request
89 */
90 public T buildConditionalRequestFromVariants(final T request, final Collection<ETag> variants) {
91 final T newRequest = messageCopier.create(request);
92 final CharArrayBuffer buffer = new CharArrayBuffer(256);
93 buffer.append(HttpHeaders.IF_NONE_MATCH);
94 buffer.append(": ");
95 int i = 0;
96 for (final ETag variant : variants) {
97 if (i > 0) {
98 buffer.append(", ");
99 }
100 variant.format(buffer);
101 i++;
102 }
103 newRequest.setHeader(BufferedHeader.create(buffer));
104 return newRequest;
105 }
106
107 /**
108 * Returns a request to unconditionally validate a cache entry with
109 * the origin. In certain cases (due to multiple intervening caches)
110 * our cache may actually receive a response to a normal conditional
111 * validation where the Date header is actually older than that of
112 * our current cache entry. In this case, the protocol recommendation
113 * is to retry the validation and force syncup with the origin.
114 * @param request client request we are trying to satisfy
115 * @return an unconditional validation request
116 */
117 public T buildUnconditionalRequest(final T request) {
118 final T newRequest = messageCopier.create(request);
119 newRequest.addHeader(HttpHeaders.CACHE_CONTROL,HeaderConstants.CACHE_CONTROL_NO_CACHE);
120 newRequest.removeHeaders(HttpHeaders.IF_RANGE);
121 newRequest.removeHeaders(HttpHeaders.IF_MATCH);
122 newRequest.removeHeaders(HttpHeaders.IF_NONE_MATCH);
123 newRequest.removeHeaders(HttpHeaders.IF_UNMODIFIED_SINCE);
124 newRequest.removeHeaders(HttpHeaders.IF_MODIFIED_SINCE);
125 return newRequest;
126 }
127
128 }