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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.Header;
+import ch.boye.httpclientandroidlib.HeaderIterator;
+import ch.boye.httpclientandroidlib.HttpResponse;
+import ch.boye.httpclientandroidlib.HttpStatus;
+import ch.boye.httpclientandroidlib.HttpVersion;
+import ch.boye.httpclientandroidlib.ParseException;
+import ch.boye.httpclientandroidlib.ProtocolVersion;
+import ch.boye.httpclientandroidlib.TokenIterator;
+import ch.boye.httpclientandroidlib.annotation.Immutable;
+import ch.boye.httpclientandroidlib.message.BasicTokenIterator;
+import ch.boye.httpclientandroidlib.protocol.HTTP;
+import ch.boye.httpclientandroidlib.protocol.HttpContext;
+import ch.boye.httpclientandroidlib.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</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
+ */
+@Immutable
+public class DefaultConnectionReuseStrategy implements ConnectionReuseStrategy {
+
+ public static final DefaultConnectionReuseStrategy INSTANCE = new DefaultConnectionReuseStrategy();
+
+ public DefaultConnectionReuseStrategy() {
+ super();
+ }
+
+ // see interface ConnectionReuseStrategy
+ 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.
+ 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 {
+ final 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 (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;
+ }
+
+}