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Diffstat (limited to 'src/org/apache/http/impl/DefaultConnectionReuseStrategy.java')
| -rw-r--r-- | src/org/apache/http/impl/DefaultConnectionReuseStrategy.java | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/src/org/apache/http/impl/DefaultConnectionReuseStrategy.java b/src/org/apache/http/impl/DefaultConnectionReuseStrategy.java new file mode 100644 index 0000000..da1d5fd --- /dev/null +++ b/src/org/apache/http/impl/DefaultConnectionReuseStrategy.java @@ -0,0 +1,182 @@ +/* + * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk/module-main/src/main/java/org/apache/http/impl/DefaultConnectionReuseStrategy.java $ + * $Revision: 602537 $ + * $Date: 2007-12-08 11:42:06 -0800 (Sat, 08 Dec 2007) $ + * + * ==================================================================== + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + * ==================================================================== + * + * This software consists of voluntary contributions made by many + * individuals on behalf of the Apache Software Foundation. For more + * information on the Apache Software Foundation, please see + * <http://www.apache.org/>. + * + */ + +package org.apache.http.impl; + +import org.apache.http.ConnectionReuseStrategy; +import org.apache.http.HttpConnection; +import org.apache.http.HeaderIterator; +import org.apache.http.HttpEntity; +import org.apache.http.HttpResponse; +import org.apache.http.HttpVersion; +import org.apache.http.ParseException; +import org.apache.http.ProtocolVersion; +import org.apache.http.protocol.HTTP; +import org.apache.http.protocol.HttpContext; +import org.apache.http.protocol.ExecutionContext; +import org.apache.http.TokenIterator; +import org.apache.http.message.BasicTokenIterator; + +/** + * Default implementation of a strategy deciding about connection re-use. + * The default implementation first checks some basics, for example + * whether the connection is still open or whether the end of the + * request entity can be determined without closing the connection. + * If these checks pass, the tokens in the "Connection" header will + * be examined. In the absence of a "Connection" header, the + * non-standard but commonly used "Proxy-Connection" header takes + * it's role. A token "close" indicates that the connection cannot + * be reused. If there is no such token, a token "keep-alive" indicates + * that the connection should be re-used. If neither token is found, + * or if there are no "Connection" headers, the default policy for + * the HTTP version is applied. Since HTTP/1.1, connections are re-used + * by default. Up until HTTP/1.0, connections are not re-used by default. + * + * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a> + * @author <a href="mailto:rolandw at apache.org">Roland Weber</a> + * + * @version $Revision: 602537 $ + * + * @since 4.0 + */ +public class DefaultConnectionReuseStrategy + implements ConnectionReuseStrategy { + + public DefaultConnectionReuseStrategy() { + super(); + } + + // see interface ConnectionReuseStrategy + public boolean keepAlive(final HttpResponse response, + final HttpContext context) { + if (response == null) { + throw new IllegalArgumentException + ("HTTP response may not be null."); + } + if (context == null) { + throw new IllegalArgumentException + ("HTTP context may not be null."); + } + + HttpConnection conn = (HttpConnection) + context.getAttribute(ExecutionContext.HTTP_CONNECTION); + + if (conn != null && !conn.isOpen()) + return false; + // do NOT check for stale connection, that is an expensive operation + + // Check for a self-terminating entity. If the end of the entity will + // be indicated by closing the connection, there is no keep-alive. + HttpEntity entity = response.getEntity(); + ProtocolVersion ver = response.getStatusLine().getProtocolVersion(); + if (entity != null) { + if (entity.getContentLength() < 0) { + if (!entity.isChunked() || + ver.lessEquals(HttpVersion.HTTP_1_0)) { + // if the content length is not known and is not chunk + // encoded, the connection cannot be reused + return false; + } + } + } + + // Check for the "Connection" header. If that is absent, check for + // the "Proxy-Connection" header. The latter is an unspecified and + // broken but unfortunately common extension of HTTP. + HeaderIterator hit = response.headerIterator(HTTP.CONN_DIRECTIVE); + if (!hit.hasNext()) + hit = response.headerIterator("Proxy-Connection"); + + // Experimental usage of the "Connection" header in HTTP/1.0 is + // documented in RFC 2068, section 19.7.1. A token "keep-alive" is + // used to indicate that the connection should be persistent. + // Note that the final specification of HTTP/1.1 in RFC 2616 does not + // include this information. Neither is the "Connection" header + // mentioned in RFC 1945, which informally describes HTTP/1.0. + // + // RFC 2616 specifies "close" as the only connection token with a + // specific meaning: it disables persistent connections. + // + // The "Proxy-Connection" header is not formally specified anywhere, + // but is commonly used to carry one token, "close" or "keep-alive". + // The "Connection" header, on the other hand, is defined as a + // sequence of tokens, where each token is a header name, and the + // token "close" has the above-mentioned additional meaning. + // + // To get through this mess, we treat the "Proxy-Connection" header + // in exactly the same way as the "Connection" header, but only if + // the latter is missing. We scan the sequence of tokens for both + // "close" and "keep-alive". As "close" is specified by RFC 2068, + // it takes precedence and indicates a non-persistent connection. + // If there is no "close" but a "keep-alive", we take the hint. + + if (hit.hasNext()) { + try { + TokenIterator ti = createTokenIterator(hit); + boolean keepalive = false; + while (ti.hasNext()) { + final String token = ti.nextToken(); + if (HTTP.CONN_CLOSE.equalsIgnoreCase(token)) { + return false; + } else if (HTTP.CONN_KEEP_ALIVE.equalsIgnoreCase(token)) { + // continue the loop, there may be a "close" afterwards + keepalive = true; + } + } + if (keepalive) + return true; + // neither "close" nor "keep-alive", use default policy + + } catch (ParseException px) { + // invalid connection header means no persistent connection + // we don't have logging in HttpCore, so the exception is lost + return false; + } + } + + // default since HTTP/1.1 is persistent, before it was non-persistent + return !ver.lessEquals(HttpVersion.HTTP_1_0); + } + + + /** + * Creates a token iterator from a header iterator. + * This method can be overridden to replace the implementation of + * the token iterator. + * + * @param hit the header iterator + * + * @return the token iterator + */ + protected TokenIterator createTokenIterator(HeaderIterator hit) { + return new BasicTokenIterator(hit); + } +} |