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
28 package org.apache.hc.core5.http.impl;
29
30 import java.util.Iterator;
31
32 import org.apache.hc.core5.annotation.Contract;
33 import org.apache.hc.core5.annotation.ThreadingBehavior;
34 import org.apache.hc.core5.http.ConnectionReuseStrategy;
35 import org.apache.hc.core5.http.Header;
36 import org.apache.hc.core5.http.HeaderElements;
37 import org.apache.hc.core5.http.HttpHeaders;
38 import org.apache.hc.core5.http.HttpRequest;
39 import org.apache.hc.core5.http.HttpResponse;
40 import org.apache.hc.core5.http.HttpStatus;
41 import org.apache.hc.core5.http.HttpVersion;
42 import org.apache.hc.core5.http.ProtocolVersion;
43 import org.apache.hc.core5.http.message.BasicTokenIterator;
44 import org.apache.hc.core5.http.message.MessageSupport;
45 import org.apache.hc.core5.http.protocol.HttpContext;
46 import org.apache.hc.core5.util.Args;
47
48 /**
49 * Default implementation of a strategy deciding about connection re-use. The strategy
50 * determines whether a connection is persistent or not based on the message’s protocol
51 * version and {@code Connection} header field if present. Connections will not be
52 * re-used and will close if any of these conditions is met
53 * <ul>
54 * <li>the {@code close} connection option is present in the request message</li>
55 * <li>the response message content body is incorrectly or ambiguously delineated</li>
56 * <li>the {@code close} connection option is present in the response message</li>
57 * <li>If the received protocol is {@code HTTP/1.0} (or earlier) and {@code keep-alive}
58 * connection option is not present</li>
59 * </ul>
60 * In the absence of a {@code Connection} header field, the non-standard but commonly used
61 * {@code Proxy-Connection} header field will be used instead. If no connection options are
62 * explicitly given the default policy for the HTTP version is applied. {@code HTTP/1.1}
63 * (or later) connections are re-used by default. {@code HTTP/1.0} (or earlier) connections
64 * are not re-used by default.
65 *
66 * @since 4.0
67 */
68 @Contract(threading = ThreadingBehavior.IMMUTABLE)
69 public class DefaultConnectionReuseStrategy implements ConnectionReuseStrategy {
70
71 public static final DefaultConnectionReuseStrategyeuseStrategy.html#DefaultConnectionReuseStrategy">DefaultConnectionReuseStrategy INSTANCE = new DefaultConnectionReuseStrategy();
72
73 public DefaultConnectionReuseStrategy() {
74 super();
75 }
76
77 // see interface ConnectionReuseStrategy
78 @Override
79 public boolean keepAlive(
80 final HttpRequest request, final HttpResponse response, final HttpContext context) {
81 Args.notNull(response, "HTTP response");
82
83 if (request != null) {
84 final Iterator<String> ti = new BasicTokenIterator(request.headerIterator(HttpHeaders.CONNECTION));
85 while (ti.hasNext()) {
86 final String token = ti.next();
87 if (HeaderElements.CLOSE.equalsIgnoreCase(token)) {
88 return false;
89 }
90 }
91 }
92
93 // If a HTTP 204 No Content response contains a Content-length with value > 0 or Transfer-Encoding header,
94 // don't reuse the connection. This is to avoid getting out-of-sync if a misbehaved HTTP server
95 // returns content as part of a HTTP 204 response.
96 if (response.getCode() == HttpStatus.SC_NO_CONTENT) {
97 final Header clh = response.getFirstHeader(HttpHeaders.CONTENT_LENGTH);
98 if (clh != null) {
99 try {
100 final long contentLen = Long.parseLong(clh.getValue());
101 if (contentLen > 0) {
102 return false;
103 }
104 } catch (final NumberFormatException ex) {
105 // fall through
106 }
107 }
108 if (response.containsHeader(HttpHeaders.TRANSFER_ENCODING)) {
109 return false;
110 }
111 }
112
113 // Check for a self-terminating entity. If the end of the entity will
114 // be indicated by closing the connection, there is no keep-alive.
115 final Header teh = response.getFirstHeader(HttpHeaders.TRANSFER_ENCODING);
116 if (teh != null) {
117 if (!HeaderElements.CHUNKED_ENCODING.equalsIgnoreCase(teh.getValue())) {
118 return false;
119 }
120 } else {
121 final String method = request != null ? request.getMethod() : null;
122 if (MessageSupport.canResponseHaveBody(method, response)
123 && response.countHeaders(HttpHeaders.CONTENT_LENGTH) != 1) {
124 return false;
125 }
126 }
127
128 // Check for the "Connection" header. If that is absent, check for
129 // the "Proxy-Connection" header. The latter is an unspecified and
130 // broken but unfortunately common extension of HTTP.
131 Iterator<Header> headerIterator = response.headerIterator(HttpHeaders.CONNECTION);
132 if (!headerIterator.hasNext()) {
133 headerIterator = response.headerIterator("Proxy-Connection");
134 }
135
136 final ProtocolVersion ver = context.getProtocolVersion();
137 if (headerIterator.hasNext()) {
138 if (ver.greaterEquals(HttpVersion.HTTP_1_1)) {
139 final Iterator<String> it = new BasicTokenIterator(headerIterator);
140 while (it.hasNext()) {
141 final String token = it.next();
142 if (HeaderElements.CLOSE.equalsIgnoreCase(token)) {
143 return false;
144 }
145 }
146 return true;
147 }
148 final Iterator<String> it = new BasicTokenIterator(headerIterator);
149 while (it.hasNext()) {
150 final String token = it.next();
151 if (HeaderElements.KEEP_ALIVE.equalsIgnoreCase(token)) {
152 return true;
153 }
154 }
155 return false;
156 }
157 return ver.greaterEquals(HttpVersion.HTTP_1_1);
158 }
159
160 }