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.http.impl;
29
30 import org.apache.http.ConnectionReuseStrategy;
31 import org.apache.http.Header;
32 import org.apache.http.HeaderIterator;
33 import org.apache.http.HttpHeaders;
34 import org.apache.http.HttpRequest;
35 import org.apache.http.HttpResponse;
36 import org.apache.http.HttpStatus;
37 import org.apache.http.HttpVersion;
38 import org.apache.http.ParseException;
39 import org.apache.http.ProtocolVersion;
40 import org.apache.http.TokenIterator;
41 import org.apache.http.annotation.Contract;
42 import org.apache.http.annotation.ThreadingBehavior;
43 import org.apache.http.message.BasicTokenIterator;
44 import org.apache.http.protocol.HTTP;
45 import org.apache.http.protocol.HttpContext;
46 import org.apache.http.protocol.HttpCoreContext;
47 import org.apache.http.util.Args;
48
49 /**
50 * Default implementation of a strategy deciding about connection re-use.
51 * The default implementation first checks some basics, for example
52 * whether the connection is still open or whether the end of the
53 * request entity can be determined without closing the connection.
54 * If these checks pass, the tokens in the {@code Connection} header will
55 * be examined. In the absence of a {@code Connection} header, the
56 * non-standard but commonly used {@code Proxy-Connection} header takes
57 * it's role. A token {@code close} indicates that the connection cannot
58 * be reused. If there is no such token, a token {@code keep-alive}
59 * indicates that the connection should be re-used. If neither token is found,
60 * or if there are no {@code Connection} headers, the default policy for
61 * the HTTP version is applied. Since {@code HTTP/1.1}, connections are
62 * re-used by default. Up until {@code HTTP/1.0}, connections are not
63 * re-used by default.
64 *
65 * @since 4.0
66 */
67 @Contract(threading = ThreadingBehavior.IMMUTABLE)
68 public class DefaultConnectionReuseStrategy implements ConnectionReuseStrategy {
69
70 public static final DefaultConnectionReuseStrategyml#DefaultConnectionReuseStrategy">DefaultConnectionReuseStrategy INSTANCE = new DefaultConnectionReuseStrategy();
71
72 public DefaultConnectionReuseStrategy() {
73 super();
74 }
75
76 // see interface ConnectionReuseStrategy
77 @Override
78 public boolean keepAlive(final HttpResponse response,
79 final HttpContext context) {
80 Args.notNull(response, "HTTP response");
81 Args.notNull(context, "HTTP context");
82
83 // If a HTTP 204 No Content response contains a Content-length with value > 0 or Transfer-Encoding,
84 // don't reuse the connection. This is to avoid getting out-of-sync if a misbehaved HTTP server
85 // returns content as part of a HTTP 204 response.
86 if (response.getStatusLine().getStatusCode() == HttpStatus.SC_NO_CONTENT) {
87 final Header clh = response.getFirstHeader(HTTP.CONTENT_LEN);
88 if (clh != null) {
89 try {
90 final int contentLen = Integer.parseInt(clh.getValue());
91 if (contentLen > 0) {
92 return false;
93 }
94 } catch (final NumberFormatException ex) {
95 // fall through
96 }
97 }
98
99 final Header teh = response.getFirstHeader(HTTP.TRANSFER_ENCODING);
100 if (teh != null) {
101 return false;
102 }
103 }
104
105 final HttpRequest../../org/apache/http/HttpRequest.html#HttpRequest">HttpRequest request = (HttpRequest) context.getAttribute(HttpCoreContext.HTTP_REQUEST);
106 if (request != null) {
107 try {
108 final TokenIterator ti = new BasicTokenIterator(request.headerIterator(HttpHeaders.CONNECTION));
109 while (ti.hasNext()) {
110 final String token = ti.nextToken();
111 if (HTTP.CONN_CLOSE.equalsIgnoreCase(token)) {
112 return false;
113 }
114 }
115 } catch (final ParseException px) {
116 // invalid connection header. do not re-use
117 return false;
118 }
119 }
120
121 // Check for a self-terminating entity. If the end of the entity will
122 // be indicated by closing the connection, there is no keep-alive.
123 final ProtocolVersion ver = response.getStatusLine().getProtocolVersion();
124 final Header teh = response.getFirstHeader(HTTP.TRANSFER_ENCODING);
125 if (teh != null) {
126 if (!HTTP.CHUNK_CODING.equalsIgnoreCase(teh.getValue())) {
127 return false;
128 }
129 } else {
130 if (canResponseHaveBody(request, response)) {
131 final Header[] clhs = response.getHeaders(HTTP.CONTENT_LEN);
132 // Do not reuse if not properly content-length delimited
133 if (clhs.length == 1) {
134 final Header clh = clhs[0];
135 try {
136 final long contentLen = Long.parseLong(clh.getValue());
137 if (contentLen < 0) {
138 return false;
139 }
140 } catch (final NumberFormatException ex) {
141 return false;
142 }
143 } else {
144 return false;
145 }
146 }
147 }
148
149 // Check for the "Connection" header. If that is absent, check for
150 // the "Proxy-Connection" header. The latter is an unspecified and
151 // broken but unfortunately common extension of HTTP.
152 HeaderIterator headerIterator = response.headerIterator(HTTP.CONN_DIRECTIVE);
153 if (!headerIterator.hasNext()) {
154 headerIterator = response.headerIterator("Proxy-Connection");
155 }
156
157 // Experimental usage of the "Connection" header in HTTP/1.0 is
158 // documented in RFC 2068, section 19.7.1. A token "keep-alive" is
159 // used to indicate that the connection should be persistent.
160 // Note that the final specification of HTTP/1.1 in RFC 2616 does not
161 // include this information. Neither is the "Connection" header
162 // mentioned in RFC 1945, which informally describes HTTP/1.0.
163 //
164 // RFC 2616 specifies "close" as the only connection token with a
165 // specific meaning: it disables persistent connections.
166 //
167 // The "Proxy-Connection" header is not formally specified anywhere,
168 // but is commonly used to carry one token, "close" or "keep-alive".
169 // The "Connection" header, on the other hand, is defined as a
170 // sequence of tokens, where each token is a header name, and the
171 // token "close" has the above-mentioned additional meaning.
172 //
173 // To get through this mess, we treat the "Proxy-Connection" header
174 // in exactly the same way as the "Connection" header, but only if
175 // the latter is missing. We scan the sequence of tokens for both
176 // "close" and "keep-alive". As "close" is specified by RFC 2068,
177 // it takes precedence and indicates a non-persistent connection.
178 // If there is no "close" but a "keep-alive", we take the hint.
179
180 if (headerIterator.hasNext()) {
181 try {
182 final TokenIterator ti = new BasicTokenIterator(headerIterator);
183 boolean keepalive = false;
184 while (ti.hasNext()) {
185 final String token = ti.nextToken();
186 if (HTTP.CONN_CLOSE.equalsIgnoreCase(token)) {
187 return false;
188 } else if (HTTP.CONN_KEEP_ALIVE.equalsIgnoreCase(token)) {
189 // continue the loop, there may be a "close" afterwards
190 keepalive = true;
191 }
192 }
193 if (keepalive) {
194 return true;
195 // neither "close" nor "keep-alive", use default policy
196 }
197
198 } catch (final ParseException px) {
199 // invalid connection header. do not re-use
200 return false;
201 }
202 }
203
204 // default since HTTP/1.1 is persistent, before it was non-persistent
205 return !ver.lessEquals(HttpVersion.HTTP_1_0);
206 }
207
208
209 /**
210 * Creates a token iterator from a header iterator.
211 * This method can be overridden to replace the implementation of
212 * the token iterator.
213 *
214 * @param hit the header iterator
215 *
216 * @return the token iterator
217 */
218 protected TokenIterator createTokenIterator(final HeaderIterator hit) {
219 return new BasicTokenIterator(hit);
220 }
221
222 private boolean canResponseHaveBody(final HttpRequest request, final HttpResponse response) {
223 if (request != null && request.getRequestLine().getMethod().equalsIgnoreCase("HEAD")) {
224 return false;
225 }
226 final int status = response.getStatusLine().getStatusCode();
227 return status >= HttpStatus.SC_OK
228 && status != HttpStatus.SC_NO_CONTENT
229 && status != HttpStatus.SC_NOT_MODIFIED
230 && status != HttpStatus.SC_RESET_CONTENT;
231 }
232
233 }