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/*
* ====================================================================
* 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 ch.boye.httpclientandroidlib.impl;
import ch.boye.httpclientandroidlib.ConnectionReuseStrategy;
import ch.boye.httpclientandroidlib.HttpConnection;
import ch.boye.httpclientandroidlib.HeaderIterator;
import ch.boye.httpclientandroidlib.HttpEntity;
import ch.boye.httpclientandroidlib.HttpResponse;
import ch.boye.httpclientandroidlib.HttpVersion;
import ch.boye.httpclientandroidlib.ParseException;
import ch.boye.httpclientandroidlib.ProtocolVersion;
import ch.boye.httpclientandroidlib.protocol.HTTP;
import ch.boye.httpclientandroidlib.protocol.HttpContext;
import ch.boye.httpclientandroidlib.protocol.ExecutionContext;
import ch.boye.httpclientandroidlib.TokenIterator;
import ch.boye.httpclientandroidlib.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 <code>Connection</code> header will
* be examined. In the absence of a <code>Connection</code> header, the
* non-standard but commonly used <code>Proxy-Connection</code> header takes
* it's role. A token <code>close</code> indicates that the connection cannot
* be reused. If there is no such token, a token <code>keep-alive</code>
* indicates that the connection should be re-used. If neither token is found,
* or if there are no <code>Connection</code> headers, the default policy for
* the HTTP version is applied. Since <code>HTTP/1.1</code>, connections are
* re-used by default. Up until <code>HTTP/1.0</code>, connections are not
* re-used by default.
*
* @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);
}
}
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