1 /* 2 * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/impl/DefaultConnectionReuseStrategy.java $ 3 * $Revision: 602537 $ 4 * $Date: 2007-12-08 11:42:06 -0800 (Sat, 08 Dec 2007) $ 5 * 6 * ==================================================================== 7 * Licensed to the Apache Software Foundation (ASF) under one 8 * or more contributor license agreements. See the NOTICE file 9 * distributed with this work for additional information 10 * regarding copyright ownership. The ASF licenses this file 11 * to you under the Apache License, Version 2.0 (the 12 * "License"); you may not use this file except in compliance 13 * with the License. You may obtain a copy of the License at 14 * 15 * http://www.apache.org/licenses/LICENSE-2.0 16 * 17 * Unless required by applicable law or agreed to in writing, 18 * software distributed under the License is distributed on an 19 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 20 * KIND, either express or implied. See the License for the 21 * specific language governing permissions and limitations 22 * under the License. 23 * ==================================================================== 24 * 25 * This software consists of voluntary contributions made by many 26 * individuals on behalf of the Apache Software Foundation. For more 27 * information on the Apache Software Foundation, please see 28 * <http://www.apache.org/>. 29 * 30 */ 31 32 package org.apache.http.impl; 33 34 import org.apache.http.ConnectionReuseStrategy; 35 import org.apache.http.HttpConnection; 36 import org.apache.http.HeaderIterator; 37 import org.apache.http.HttpEntity; 38 import org.apache.http.HttpResponse; 39 import org.apache.http.HttpVersion; 40 import org.apache.http.ParseException; 41 import org.apache.http.ProtocolVersion; 42 import org.apache.http.protocol.HTTP; 43 import org.apache.http.protocol.HttpContext; 44 import org.apache.http.protocol.ExecutionContext; 45 import org.apache.http.TokenIterator; 46 import org.apache.http.message.BasicTokenIterator; 47 48 /** 49 * Default implementation of a strategy deciding about connection re-use. 50 * The default implementation first checks some basics, for example 51 * whether the connection is still open or whether the end of the 52 * request entity can be determined without closing the connection. 53 * If these checks pass, the tokens in the "Connection" header will 54 * be examined. In the absence of a "Connection" header, the 55 * non-standard but commonly used "Proxy-Connection" header takes 56 * it's role. A token "close" indicates that the connection cannot 57 * be reused. If there is no such token, a token "keep-alive" indicates 58 * that the connection should be re-used. If neither token is found, 59 * or if there are no "Connection" headers, the default policy for 60 * the HTTP version is applied. Since HTTP/1.1, connections are re-used 61 * by default. Up until HTTP/1.0, connections are not re-used by default. 62 * 63 * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a> 64 * @author <a href="mailto:rolandw at apache.org">Roland Weber</a> 65 * 66 * @version $Revision: 602537 $ 67 * 68 * @since 4.0 69 * 70 * @deprecated Please use {@link java.net.URL#openConnection} instead. 71 * Please visit <a href="http://android-developers.blogspot.com/2011/09/androids-http-clients.html">this webpage</a> 72 * for further details. 73 */ 74 @Deprecated 75 public class DefaultConnectionReuseStrategy 76 implements ConnectionReuseStrategy { 77 78 public DefaultConnectionReuseStrategy() { 79 super(); 80 } 81 82 // see interface ConnectionReuseStrategy 83 public boolean keepAlive(final HttpResponse response, 84 final HttpContext context) { 85 if (response == null) { 86 throw new IllegalArgumentException 87 ("HTTP response may not be null."); 88 } 89 if (context == null) { 90 throw new IllegalArgumentException 91 ("HTTP context may not be null."); 92 } 93 94 HttpConnection conn = (HttpConnection) 95 context.getAttribute(ExecutionContext.HTTP_CONNECTION); 96 97 if (conn != null && !conn.isOpen()) 98 return false; 99 // do NOT check for stale connection, that is an expensive operation 100 101 // Check for a self-terminating entity. If the end of the entity will 102 // be indicated by closing the connection, there is no keep-alive. 103 HttpEntity entity = response.getEntity(); 104 ProtocolVersion ver = response.getStatusLine().getProtocolVersion(); 105 if (entity != null) { 106 if (entity.getContentLength() < 0) { 107 if (!entity.isChunked() || 108 ver.lessEquals(HttpVersion.HTTP_1_0)) { 109 // if the content length is not known and is not chunk 110 // encoded, the connection cannot be reused 111 return false; 112 } 113 } 114 } 115 116 // Check for the "Connection" header. If that is absent, check for 117 // the "Proxy-Connection" header. The latter is an unspecified and 118 // broken but unfortunately common extension of HTTP. 119 HeaderIterator hit = response.headerIterator(HTTP.CONN_DIRECTIVE); 120 if (!hit.hasNext()) 121 hit = response.headerIterator("Proxy-Connection"); 122 123 // Experimental usage of the "Connection" header in HTTP/1.0 is 124 // documented in RFC 2068, section 19.7.1. A token "keep-alive" is 125 // used to indicate that the connection should be persistent. 126 // Note that the final specification of HTTP/1.1 in RFC 2616 does not 127 // include this information. Neither is the "Connection" header 128 // mentioned in RFC 1945, which informally describes HTTP/1.0. 129 // 130 // RFC 2616 specifies "close" as the only connection token with a 131 // specific meaning: it disables persistent connections. 132 // 133 // The "Proxy-Connection" header is not formally specified anywhere, 134 // but is commonly used to carry one token, "close" or "keep-alive". 135 // The "Connection" header, on the other hand, is defined as a 136 // sequence of tokens, where each token is a header name, and the 137 // token "close" has the above-mentioned additional meaning. 138 // 139 // To get through this mess, we treat the "Proxy-Connection" header 140 // in exactly the same way as the "Connection" header, but only if 141 // the latter is missing. We scan the sequence of tokens for both 142 // "close" and "keep-alive". As "close" is specified by RFC 2068, 143 // it takes precedence and indicates a non-persistent connection. 144 // If there is no "close" but a "keep-alive", we take the hint. 145 146 if (hit.hasNext()) { 147 try { 148 TokenIterator ti = createTokenIterator(hit); 149 boolean keepalive = false; 150 while (ti.hasNext()) { 151 final String token = ti.nextToken(); 152 if (HTTP.CONN_CLOSE.equalsIgnoreCase(token)) { 153 return false; 154 } else if (HTTP.CONN_KEEP_ALIVE.equalsIgnoreCase(token)) { 155 // continue the loop, there may be a "close" afterwards 156 keepalive = true; 157 } 158 } 159 if (keepalive) 160 return true; 161 // neither "close" nor "keep-alive", use default policy 162 163 } catch (ParseException px) { 164 // invalid connection header means no persistent connection 165 // we don't have logging in HttpCore, so the exception is lost 166 return false; 167 } 168 } 169 170 // default since HTTP/1.1 is persistent, before it was non-persistent 171 return !ver.lessEquals(HttpVersion.HTTP_1_0); 172 } 173 174 175 /** 176 * Creates a token iterator from a header iterator. 177 * This method can be overridden to replace the implementation of 178 * the token iterator. 179 * 180 * @param hit the header iterator 181 * 182 * @return the token iterator 183 */ 184 protected TokenIterator createTokenIterator(HeaderIterator hit) { 185 return new BasicTokenIterator(hit); 186 } 187 } 188
