/*
* ====================================================================
* 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.Header;
import org.apache.http.HeaderIterator;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.HttpVersion;
import org.apache.http.ParseException;
import org.apache.http.ProtocolVersion;
import org.apache.http.TokenIterator;
import org.apache.http.annotation.Immutable;
import org.apache.http.message.BasicHeaderIterator;
import org.apache.http.message.BasicTokenIterator;
import org.apache.http.protocol.HTTP;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.Args;
/**
* 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} header will
* be examined. In the absence of a {@code Connection} header, the
* non-standard but commonly used {@code Proxy-Connection} header takes
* it's role. A token {@code close} indicates that the connection cannot
* be reused. If there is no such token, a token {@code keep-alive}
* indicates that the connection should be re-used. If neither token is found,
* or if there are no {@code Connection} headers, the default policy for
* the HTTP version is applied. Since {@code HTTP/1.1}, connections are
* re-used by default. Up until {@code HTTP/1.0}, connections are not
* re-used by default.
*
* @since 4.0
*/
@Immutable
public class DefaultConnectionReuseStrategy implements ConnectionReuseStrategy {
public static final DefaultConnectionReuseStrategy INSTANCE = new DefaultConnectionReuseStrategy();
public DefaultConnectionReuseStrategy() {
super();
}
// see interface ConnectionReuseStrategy
@Override
public boolean keepAlive(final HttpResponse response,
final HttpContext context) {
Args.notNull(response, "HTTP response");
Args.notNull(context, "HTTP context");
// Check for a self-terminating entity. If the end of the entity will
// be indicated by closing the connection, there is no keep-alive.
final ProtocolVersion ver = response.getStatusLine().getProtocolVersion();
final Header teh = response.getFirstHeader(HTTP.TRANSFER_ENCODING);
if (teh != null) {
if (!HTTP.CHUNK_CODING.equalsIgnoreCase(teh.getValue())) {
return false;
}
} else {
if (canResponseHaveBody(response)) {
final Header[] clhs = response.getHeaders(HTTP.CONTENT_LEN);
// Do not reuse if not properly content-length delimited
if (clhs.length == 1) {
final Header clh = clhs[0];
try {
final int contentLen = Integer.parseInt(clh.getValue());
if (contentLen < 0) {
return false;
}
} catch (final NumberFormatException ex) {
return false;
}
} else {
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.
Header[] connHeaders = response.getHeaders(HTTP.CONN_DIRECTIVE);
if (connHeaders.length == 0) {
connHeaders = response.getHeaders("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 (connHeaders.length != 0) {
try {
final TokenIterator ti = new BasicTokenIterator(new BasicHeaderIterator(connHeaders, null));
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 (final 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(final HeaderIterator hit) {
return new BasicTokenIterator(hit);
}
private boolean canResponseHaveBody(final HttpResponse response) {
final int status = response.getStatusLine().getStatusCode();
return status >= HttpStatus.SC_OK
&& status != HttpStatus.SC_NO_CONTENT
&& status != HttpStatus.SC_NOT_MODIFIED
&& status != HttpStatus.SC_RESET_CONTENT;
}
}