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