JDK下sun.net.www.protocol.http.HttpURLConnection类-----Http客户端实现类的实现分析

HttpClient类是进行TCP连接的实现类，

package sun.net.www.http;

import java.io.*;
import java.net.*;
import java.util.*;
import sun.net.NetworkClient;
import sun.net.ProgressSource;
import sun.net.ProgressMonitor;
import sun.net.www.MessageHeader;
import sun.net.www.HeaderParser;
import sun.net.www.MeteredStream;
import sun.net.www.ParseUtil;
import sun.net.www.protocol.http.HttpURLConnection;
import sun.misc.RegexpPool;

import java.security.*;
/**
* @author Herb Jellinek
* @author Dave Brown
*/
public class HttpClient extends NetworkClient {
// whether this httpclient comes from the cache
protected boolean cachedHttpClient = false;

private boolean inCache;

protected CookieHandler cookieHandler;

// Http requests we send
MessageHeader requests;

// Http data we send with the headers
PosterOutputStream poster = null;

// if we've had one io error
boolean failedOnce = false;

/** regexp pool of hosts for which we should connect directly, not Proxy
*  these are intialized from a property.
*/
private static RegexpPool nonProxyHostsPool = null;

/** The string source of nonProxyHostsPool
*/
private static String nonProxyHostsSource = null;

/** Response code for CONTINUE */
private static final int    HTTP_CONTINUE = 100;

/** Default port number for http daemons. REMIND: make these private */
static final int    httpPortNumber = 80;

/** return default port number (subclasses may override) */
protected int getDefaultPort () { return httpPortNumber; }

static private int getDefaultPort(String proto) {
if ("http".equalsIgnoreCase(proto))
return 80;
if ("https".equalsIgnoreCase(proto))
return 443;
return -1;
}

/* The following three data members are left in for binary */
/* backwards-compatibility.  Unfortunately, HotJava sets them directly */
/* when it wants to change the settings.  The new design has us not */
/* cache these, so this is unnecessary, but eliminating the data members */
/* would break HJB 1.1 under JDK 1.2. */
/* */
/* These data members are not used, and their values are meaningless. */
/* REMIND:  Take them out for JDK 2.0! */
/**
* @deprecated
*/
//    public static String proxyHost = null;
/**
* @deprecated
*/
//    public static int proxyPort = 80;

/* instance-specific proxy fields override the static fields if set.
* Used by FTP.  These are set to the true proxy host/port if
* usingProxy is true.
*/
//    private String instProxy = null;
//    private int instProxyPort = -1;

/* All proxying (generic as well as instance-specific) may be
* disabled through use of this flag
*/
protected boolean proxyDisabled;

// are we using proxy in this instance?
public boolean usingProxy = false;
// target host, port for the URL
protected String host;
protected int port;

/* where we cache currently open, persistent connections */
protected static KeepAliveCache kac = new KeepAliveCache();

private static boolean keepAliveProp = true;

// retryPostProp is true by default so as to preserve behavior
// from previous releases.
private static boolean retryPostProp = true;

volatile boolean keepingAlive = false;     /* this is a keep-alive connection */
int keepAliveConnections = -1;    /* number of keep-alives left */

/**Idle timeout value, in milliseconds. Zero means infinity,
* iff keepingAlive=true.
* Unfortunately, we can't always believe this one.  If I'm connected
* through a Netscape proxy to a server that sent me a keep-alive
* time of 15 sec, the proxy unilaterally terminates my connection
* after 5 sec.  So we have to hard code our effective timeout to
* 4 sec for the case where we're using a proxy. *SIGH*
*/
int keepAliveTimeout = 0;

/** whether the response is to be cached */
private CacheRequest cacheRequest = null;

/** Url being fetched. */
protected URL       url;

/* if set, the client will be reused and must not be put in cache */
public boolean reuse = false;

/**
* A NOP method kept for backwards binary compatibility
* @deprecated -- system properties are no longer cached.
*/
@Deprecated
public static synchronized void resetProperties() {
}

int getKeepAliveTimeout() {
return keepAliveTimeout;
}

static {
String keepAlive = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("http.keepAlive"));

String retryPost = java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("sun.net.http.retryPost"));

if (keepAlive != null) {
keepAliveProp = Boolean.valueOf(keepAlive).booleanValue();
} else {
keepAliveProp = true;
}

if (retryPost != null) {
retryPostProp = Boolean.valueOf(retryPost).booleanValue();
} else
retryPostProp = true;

}

/**
* @return true iff http keep alive is set (i.e. enabled).  Defaults
*          to true if the system property http.keepAlive isn't set.
*/
public boolean getHttpKeepAliveSet() {
return keepAliveProp;
}

protected HttpClient() {
}

private HttpClient(URL url)
throws IOException {
this(url, (String)null, -1, false);
}

protected HttpClient(URL url,
boolean proxyDisabled) throws IOException {
this(url, null, -1, proxyDisabled);
}

/* This package-only CTOR should only be used for FTP piggy-backed on HTTP
* HTTP URL's that use this won't take advantage of keep-alive.
* Additionally, this constructor may be used as a last resort when the
* first HttpClient gotten through New() failed (probably b/c of a
* Keep-Alive mismatch).
*
* XXX That documentation is wrong ... it's not package-private any more
*/
public HttpClient(URL url, String proxyHost, int proxyPort)
throws IOException {
this(url, proxyHost, proxyPort, false);
}
//该构造方法的最后一行openserver()方法进行了TCP连接
protected HttpClient(URL url, Proxy p, int to) throws IOException {
proxy = (p == null) ? Proxy.NO_PROXY : p;
this.host = url.getHost();
this.url = url;
port = url.getPort();
if (port == -1) {
port = getDefaultPort();
}
setConnectTimeout(to);

// get the cookieHandler if there is any
cookieHandler = (CookieHandler)java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
return CookieHandler.getDefault();
}
});

openServer();
}

static protected Proxy newHttpProxy(String proxyHost, int proxyPort,
String proto) {
if (proxyHost == null || proto == null)
return Proxy.NO_PROXY;
int pport = proxyPort < 0 ? getDefaultPort(proto) : proxyPort;
InetSocketAddress saddr = InetSocketAddress.createUnresolved(proxyHost, pport);
return new Proxy(Proxy.Type.HTTP, saddr);
}

/*
* This constructor gives "ultimate" flexibility, including the ability
* to bypass implicit proxying.  Sometimes we need to be using tunneling
* (transport or network level) instead of proxying (application level),
* for example when we don't want the application level data to become
* visible to third parties.
*
* @param url               the URL to which we're connecting
* @param proxy             proxy to use for this URL (e.g. forwarding)
* @param proxyPort         proxy port to use for this URL
* @param proxyDisabled     true to disable default proxying
*/
private HttpClient(URL url, String proxyHost, int proxyPort,
boolean proxyDisabled)
throws IOException {
this(url, proxyDisabled ? Proxy.NO_PROXY :
newHttpProxy(proxyHost, proxyPort, "http"), -1);
}

public HttpClient(URL url, String proxyHost, int proxyPort,
boolean proxyDisabled, int to)
throws IOException {
this(url, proxyDisabled ? Proxy.NO_PROXY :
newHttpProxy(proxyHost, proxyPort, "http"), to);
}

/* This class has no public constructor for HTTP.  This method is used to
* get an HttpClient to the specifed URL.  If there's currently an
* active HttpClient to that server/port, you'll get that one.
*/
public static HttpClient New(URL url)
throws IOException {
return HttpClient.New(url, Proxy.NO_PROXY, -1, true);
}

public static HttpClient New(URL url, boolean useCache)
throws IOException {
return HttpClient.New(url, Proxy.NO_PROXY, -1, useCache);
}

public static HttpClient New(URL url, Proxy p, int to, boolean useCache)
throws IOException {
if (p == null) {
p = Proxy.NO_PROXY;
}
HttpClient ret = null;
/* see if one's already around */
if (useCache) {
ret = (HttpClient) kac.get(url, null);
if (ret != null) {
if ((ret.proxy != null && ret.proxy.equals(p)) ||
(ret.proxy == null && p == null)) {
synchronized (ret) {
ret.cachedHttpClient = true;
assert ret.inCache;
ret.inCache = false;
}
} else {
// We cannot return this connection to the cache as it's
// KeepAliveTimeout will get reset. We simply close the connection.
// This should be fine as it is very rare that a connection
// to the same host will not use the same proxy.
ret.inCache = false;
ret.closeServer();
ret = null;
}
}
}
if (ret == null) {
ret = new HttpClient(url, p, to);
} else {
SecurityManager security = System.getSecurityManager();
if (security != null) {
if (ret.proxy == Proxy.NO_PROXY || ret.proxy == null) {
security.checkConnect(InetAddress.getByName(url.getHost()).getHostAddress(),
url.getPort());
} else {
security.checkConnect(url.getHost(), url.getPort());
}
}
ret.url = url;
}
return ret;
}

public static HttpClient New(URL url, Proxy p, int to) throws IOException {
return New(url, p, to, true);
}

public static HttpClient New(URL url, String proxyHost, int proxyPort,
boolean useCache)
throws IOException {
return New(url, newHttpProxy(proxyHost, proxyPort, "http"), -1, useCache);
}

public static HttpClient New(URL url, String proxyHost, int proxyPort,
boolean useCache, int to)
throws IOException {
return New(url, newHttpProxy(proxyHost, proxyPort, "http"), to, useCache);
}

/* return it to the cache as still usable, if:
* 1) It's keeping alive, AND
* 2) It still has some connections left, AND
* 3) It hasn't had a error (PrintStream.checkError())
* 4) It hasn't timed out
*
* If this client is not keepingAlive, it should have been
* removed from the cache in the parseHeaders() method.
*/

public void finished() {
if (reuse) /* will be reused */
return;
keepAliveConnections--;
poster = null;
if (keepAliveConnections > 0 && isKeepingAlive() &&
!(serverOutput.checkError())) {
/* This connection is keepingAlive && still valid.
* Return it to the cache.
*/
putInKeepAliveCache();
} else {
closeServer();
}
}

protected synchronized void putInKeepAliveCache() {
if (inCache) {
assert false : "Duplicate put to keep alive cache";
return;
}
inCache = true;
kac.put(url, null, this);
}

protected boolean isInKeepAliveCache() {
return inCache;
}

/*
* Close an idle connection to this URL (if it exists in the
* cache).
*/
public void closeIdleConnection() {
HttpClient http = (HttpClient) kac.get(url, null);
if (http != null) {
http.closeServer();
}
}

/* We're very particular here about what our InputStream to the server
* looks like for reasons that are apparent if you can decipher the
* method parseHTTP().  That's why this method is overidden from the
* superclass.
* server ： 要连接的IP port：要连接的端口
*/
public void openServer(String server, int port) throws IOException {
//serverSocket对象是一个Socket对象，是建立连接之后返回的Socket对象，调用父类NetworkClient类的doConnect方法
serverSocket = doConnect(server, port);
try {
serverOutput = new PrintStream(
new BufferedOutputStream(serverSocket.getOutputStream()),
false, encoding);
} catch (UnsupportedEncodingException e) {
throw new InternalError(encoding+" encoding not found");
}
serverSocket.setTcpNoDelay(true);
}

/*
* Returns true if the http request should be tunneled through proxy.
* An example where this is the case is Https.
*/
public boolean needsTunneling() {
return false;
}

/*
* Returns true if this httpclient is from cache
*/
public boolean isCachedConnection() {
return cachedHttpClient;
}

/*
* Finish any work left after the socket connection is
* established.  In the normal http case, it's a NO-OP. Subclass
* may need to override this. An example is Https, where for
* direct connection to the origin server, ssl handshake needs to
* be done; for proxy tunneling, the socket needs to be converted
* into an SSL socket before ssl handshake can take place.
*/
public void afterConnect() throws IOException, UnknownHostException {
// NO-OP. Needs to be overwritten by HttpsClient
}

/*
* call openServer in a privileged block
*/
private synchronized void privilegedOpenServer(final InetSocketAddress server)
throws IOException
{
try {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedExceptionAction() {
public Object run() throws IOException {
openServer(server.getHostName(), server.getPort());
return null;
}
});
} catch (java.security.PrivilegedActionException pae) {
throw (IOException) pae.getException();
}
}

/*
* call super.openServer
*/
private void superOpenServer(final String proxyHost,
final int proxyPort)
throws IOException, UnknownHostException
{
super.openServer(proxyHost, proxyPort);
}

/*
* call super.openServer in a privileged block
*/
private synchronized void privilegedSuperOpenServer(final String proxyHost,
final int proxyPort)
throws IOException
{
try {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedExceptionAction() {
public Object run() throws IOException
{
superOpenServer(proxyHost, proxyPort);
return null;
}
});
} catch (java.security.PrivilegedActionException pae) {
throw (IOException) pae.getException();
}
}

/*
*无参数的openServer方法，实现开启TCP连接工作
*/
protected synchronized void openServer() throws IOException {

SecurityManager security = System.getSecurityManager();

if (keepingAlive) { // already opened
if (security != null) {
security.checkConnect(host, port);
}

return;
}

String urlHost = url.getHost().toLowerCase();

if (url.getProtocol().equals("http") ||
url.getProtocol().equals("https") ) {

if ((proxy != null) && (proxy.type() == Proxy.Type.HTTP)) {
sun.net.www.URLConnection.setProxiedHost(host);
if (security != null) {
security.checkConnect(host, port);
}
privilegedOpenServer((InetSocketAddress) proxy.address());
usingProxy = true;
return;
} else {
// make direct connection
if (security != null) {
// redundant?
security.checkConnect(host, port);
}
　　　　　　　　　//调用有参构造方法，传入要连接的host和port
openServer(host, port);
usingProxy = false;
return;
}

} else {
/* we're opening some other kind of url, most likely an
* ftp url.
*/
if ((proxy != null) && (proxy.type() == Proxy.Type.HTTP)) {
sun.net.www.URLConnection.setProxiedHost(host);
if (security != null) {
security.checkConnect(host, port);
}
privilegedOpenServer((InetSocketAddress) proxy.address());
usingProxy = true;
return;
} else {
// make direct connection
if (security != null) {
// redundant?
security.checkConnect(host, port);
}
super.openServer(host, port);
usingProxy = false;
return;
}
}
}

public String getURLFile() throws IOException {

String fileName = url.getFile();
if ((fileName == null) || (fileName.length() == 0))
fileName = "/";

/**
* proxyDisabled is set by subclass HttpsClient!
*/
if (usingProxy && !proxyDisabled) {
// Do not use URLStreamHandler.toExternalForm as the fragment
// should not be part of the RequestURI. It should be an
// absolute URI which does not have a fragment part.
StringBuffer result = new StringBuffer(128);
result.append(url.getProtocol());
result.append(":");
if (url.getAuthority() != null && url.getAuthority().length() > 0) {
result.append("//");
result.append(url.getAuthority());
}
if (url.getPath() != null) {
result.append(url.getPath());
}
if (url.getQuery() != null) {
result.append('?');
result.append(url.getQuery());
}

fileName =  result.toString();
}
if (fileName.indexOf('\n') == -1)
return fileName;
else
throw new java.net.MalformedURLException("Illegal character in URL");
}

/**
* @deprecated
*/
@Deprecated
public void writeRequests(MessageHeader head) {
requests = head;
requests.print(serverOutput);
serverOutput.flush();
}

public void writeRequests(MessageHeader head,
PosterOutputStream pos) throws IOException {
requests = head;
requests.print(serverOutput);
poster = pos;
if (poster != null)
poster.writeTo(serverOutput);
serverOutput.flush();
}

/** Parse the first line of the HTTP request.  It usually looks
something like: "HTTP/1.0 <number> comment\r\n". */

public boolean parseHTTP(MessageHeader responses, ProgressSource pi, HttpURLConnection httpuc)
throws IOException {
/* If "HTTP/*" is found in the beginning, return true.  Let
* HttpURLConnection parse the mime header itself.
*
* If this isn't valid HTTP, then we don't try to parse a header
* out of the beginning of the response into the responses,
* and instead just queue up the output stream to it's very beginning.
* This seems most reasonable, and is what the NN browser does.
*/

try {
serverInput = serverSocket.getInputStream();
serverInput = new BufferedInputStream(serverInput);
return (parseHTTPHeader(responses, pi, httpuc));
} catch (SocketTimeoutException stex) {
// We don't want to retry the request when the app. sets a timeout
closeServer();
throw stex;
} catch (IOException e) {
closeServer();
cachedHttpClient = false;
if (!failedOnce && requests != null) {
if (httpuc.getRequestMethod().equals("POST") && !retryPostProp) {
// do not retry the request
}  else {
// try once more
failedOnce = true;
openServer();
if (needsTunneling()) {
httpuc.doTunneling();
}
afterConnect();
writeRequests(requests, poster);
return parseHTTP(responses, pi, httpuc);
}
}
throw e;
}

}

public int setTimeout (int timeout) throws SocketException {
int old = serverSocket.getSoTimeout ();
serverSocket.setSoTimeout (timeout);
return old;
}

private boolean parseHTTPHeader(MessageHeader responses, ProgressSource pi, HttpURLConnection httpuc)
throws IOException {
/* If "HTTP/*" is found in the beginning, return true.  Let
* HttpURLConnection parse the mime header itself.
*
* If this isn't valid HTTP, then we don't try to parse a header
* out of the beginning of the response into the responses,
* and instead just queue up the output stream to it's very beginning.
* This seems most reasonable, and is what the NN browser does.
*/

keepAliveConnections = -1;
keepAliveTimeout = 0;

boolean ret = false;
byte[] b = new byte[8];

try {
int nread = 0;
serverInput.mark(10);
while (nread < 8) {
int r = serverInput.read(b, nread, 8 - nread);
if (r < 0) {
break;
}
nread += r;
}
String keep=null;
ret = b[0] == 'H' && b[1] == 'T'
&& b[2] == 'T' && b[3] == 'P' && b[4] == '/' &&
b[5] == '1' && b[6] == '.';
serverInput.reset();
if (ret) { // is valid HTTP - response started w/ "HTTP/1."
responses.parseHeader(serverInput);

// we've finished parsing http headers
// check if there are any applicable cookies to set (in cache)
if (cookieHandler != null) {
URI uri = ParseUtil.toURI(url);
// NOTE: That cast from Map shouldn't be necessary but
// a bug in javac is triggered under certain circumstances
// So we do put the cast in as a workaround until
// it is resolved.
if (uri != null)
cookieHandler.put(uri, (Map<java.lang.String,java.util.List<java.lang.String>>)responses.getHeaders());
}

/* decide if we're keeping alive:
* This is a bit tricky.  There's a spec, but most current
* servers (10/1/96) that support this differ in dialects.
* If the server/client misunderstand each other, the
* protocol should fall back onto HTTP/1.0, no keep-alive.
*/
if (usingProxy) { // not likely a proxy will return this
keep = responses.findValue("Proxy-Connection");
}
if (keep == null) {
keep = responses.findValue("Connection");
}
if (keep != null && keep.toLowerCase().equals("keep-alive")) {
/* some servers, notably Apache1.1, send something like:
* "Keep-Alive: timeout=15, max=1" which we should respect.
*/
HeaderParser p = new HeaderParser(
responses.findValue("Keep-Alive"));
if (p != null) {
/* default should be larger in case of proxy */
keepAliveConnections = p.findInt("max", usingProxy?50:5);
keepAliveTimeout = p.findInt("timeout", usingProxy?60:5);
}
} else if (b[7] != '0') {
/*
* We're talking 1.1 or later. Keep persistent until
* the server says to close.
*/
if (keep != null) {
/*
* The only Connection token we understand is close.
* Paranoia: if there is any Connection header then
* treat as non-persistent.
*/
keepAliveConnections = 1;
} else {
keepAliveConnections = 5;
}
}
} else if (nread != 8) {
if (!failedOnce && requests != null) {
if (httpuc.getRequestMethod().equals("POST") && !retryPostProp) {
// do not retry the request
} else {
failedOnce = true;
closeServer();
cachedHttpClient = false;
openServer();
if (needsTunneling()) {
httpuc.doTunneling();
}
afterConnect();
writeRequests(requests, poster);
return parseHTTP(responses, pi, httpuc);
}
}
throw new SocketException("Unexpected end of file from server");
} else {
// we can't vouche for what this is....
responses.set("Content-type", "unknown/unknown");
}
} catch (IOException e) {
throw e;
}

int code = -1;
try {
String resp;
resp = responses.getValue(0);
/* should have no leading/trailing LWS
* expedite the typical case by assuming it has
* form "HTTP/1.x <WS> 2XX <mumble>"
*/
int ind;
ind = resp.indexOf(' ');
while(resp.charAt(ind) == ' ')
ind++;
code = Integer.parseInt(resp.substring(ind, ind + 3));
} catch (Exception e) {}

if (code == HTTP_CONTINUE) {
responses.reset();
return parseHTTPHeader(responses, pi, httpuc);
}

int cl = -1;

/*
* Set things up to parse the entity body of the reply.
* We should be smarter about avoid pointless work when
* the HTTP method and response code indicate there will be
* no entity body to parse.
*/
String te = null;
try {
te = responses.findValue("Transfer-Encoding");
} catch (Exception e) {}
if (te != null && te.equalsIgnoreCase("chunked")) {
serverInput = new ChunkedInputStream(serverInput, this, responses);

/*
* If keep alive not specified then close after the stream
* has completed.
*/
if (keepAliveConnections <= 1) {
keepAliveConnections = 1;
keepingAlive = false;
} else {
keepingAlive = true;
}
failedOnce = false;
} else {

/*
* If it's a keep alive connection then we will keep
* (alive if :-
* 1. content-length is specified, or
* 2. "Not-Modified" or "No-Content" responses - RFC 2616 states that
*    204 or 304 response must not include a message body.
*/
try {
cl = Integer.parseInt(responses.findValue("content-length"));
} catch (Exception e) {}

String requestLine = requests.getKey(0);

if ((requestLine != null &&
(requestLine.startsWith("HEAD"))) ||
code == HttpURLConnection.HTTP_NOT_MODIFIED ||
code == HttpURLConnection.HTTP_NO_CONTENT) {
cl = 0;
}

if (keepAliveConnections > 1 &&
(cl >= 0 ||
code == HttpURLConnection.HTTP_NOT_MODIFIED ||
code == HttpURLConnection.HTTP_NO_CONTENT)) {
keepingAlive = true;
failedOnce = false;
} else if (keepingAlive) {
/* Previously we were keeping alive, and now we're not.  Remove
* this from the cache (but only here, once) - otherwise we get
* multiple removes and the cache count gets messed up.
*/
keepingAlive=false;
}
}

/* wrap a KeepAliveStream/MeteredStream around it if appropriate */

if (cl > 0) {
// In this case, content length is well known, so it is okay
// to wrap the input stream with KeepAliveStream/MeteredStream.

if (pi != null) {
// Progress monitor is enabled
pi.setContentType(responses.findValue("content-type"));
}

if (isKeepingAlive())   {
// Wrap KeepAliveStream if keep alive is enabled.
serverInput = new KeepAliveStream(serverInput, pi, cl, this);
failedOnce = false;
}
else        {
serverInput = new MeteredStream(serverInput, pi, cl);
}
}
else if (cl == -1)  {
// In this case, content length is unknown - the input
// stream would simply be a regular InputStream or
// ChunkedInputStream.

if (pi != null) {
// Progress monitoring is enabled.

pi.setContentType(responses.findValue("content-type"));

// Wrap MeteredStream for tracking indeterministic
// progress, even if the input stream is ChunkedInputStream.
serverInput = new MeteredStream(serverInput, pi, cl);
}
else    {
// Progress monitoring is disabled, and there is no
// need to wrap an unknown length input stream.

// ** This is an no-op **
}
}
else    {
if (pi != null)
pi.finishTracking();
}

return ret;
}

public synchronized InputStream getInputStream() {
return serverInput;
}

public OutputStream getOutputStream() {
return serverOutput;
}

public String toString() {
return getClass().getName()+"("+url+")";
}

public final boolean isKeepingAlive() {
return getHttpKeepAliveSet() && keepingAlive;
}

public void setCacheRequest(CacheRequest cacheRequest) {
this.cacheRequest = cacheRequest;
}

CacheRequest getCacheRequest() {
return cacheRequest;
}

protected void finalize() throws Throwable {
// This should do nothing.  The stream finalizer will
// close the fd.
}

public void setDoNotRetry(boolean value) {
// failedOnce is used to determine if a request should be retried.
failedOnce = value;
}

/* Use only on connections in error. */
public void closeServer() {
try {
keepingAlive = false;
serverSocket.close();
} catch (Exception e) {}
}

/**
* @return the proxy host being used for this client, or null
*          if we're not going through a proxy
*/
public String getProxyHostUsed() {
if (!usingProxy) {
return null;
} else {
return ((InetSocketAddress)proxy.address()).getHostName();
}
}

/**
* @return the proxy port being used for this client.  Meaningless
*          if getProxyHostUsed() gives null.
*/
public int getProxyPortUsed() {
if (usingProxy)
return ((InetSocketAddress)proxy.address()).getPort();
return -1;
}
}

/*
* Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.  Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.net;

import java.io.*;
import java.net.Socket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.net.Proxy;
import java.util.Arrays;
import java.security.AccessController;
import java.security.PrivilegedAction;

/**
* This is the base class for network clients.
*
* @author      Jonathan Payne
*/
public class NetworkClient {
protected Proxy     proxy = Proxy.NO_PROXY;
/** Socket for communicating with server. */
protected Socket    serverSocket = null;

/** Stream for printing to the server. */
public PrintStream  serverOutput;

/** Buffered stream for reading replies from server. */
public InputStream  serverInput;

protected static int defaultSoTimeout;
protected static int defaultConnectTimeout;

protected int readTimeout = -1;
protected int connectTimeout = -1;
/* Name of encoding to use for output */
protected static String encoding;

static {
final int vals[] = {0, 0};
final String encs[] = { null };

AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
vals[0] = Integer.getInteger("sun.net.client.defaultReadTimeout", 0).intValue();
vals[1] = Integer.getInteger("sun.net.client.defaultConnectTimeout", 0).intValue();
encs[0] = System.getProperty("file.encoding", "ISO8859_1");
return null;
}
});
if (vals[0] == 0)
defaultSoTimeout = -1;
else
defaultSoTimeout = vals[0];

if (vals[1] == 0)
defaultConnectTimeout = -1;
else
defaultConnectTimeout = vals[1];

encoding = encs[0];
try {
if (!isASCIISuperset (encoding)) {
encoding = "ISO8859_1";
}
} catch (Exception e) {
encoding = "ISO8859_1";
}
}

/**
* Test the named character encoding to verify that it converts ASCII
* characters correctly. We have to use an ASCII based encoding, or else
* the NetworkClients will not work correctly in EBCDIC based systems.
* However, we cannot just use ASCII or ISO8859_1 universally, because in
* Asian locales, non-ASCII characters may be embedded in otherwise
* ASCII based protocols (eg. HTTP). The specifications (RFC2616, 2398)
* are a little ambiguous in this matter. For instance, RFC2398 [part 2.1]
* says that the HTTP request URI should be escaped using a defined
* mechanism, but there is no way to specify in the escaped string what
* the original character set is. It is not correct to assume that
* UTF-8 is always used (as in URLs in HTML 4.0).  For this reason,
* until the specifications are updated to deal with this issue more
* comprehensively, and more importantly, HTTP servers are known to
* support these mechanisms, we will maintain the current behavior
* where it is possible to send non-ASCII characters in their original
* unescaped form.
*/
private static boolean isASCIISuperset (String encoding) throws Exception {
String chkS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"+
"abcdefghijklmnopqrstuvwxyz-_.!~*'();/?:@&=+$,";

// Expected byte sequence for string above
byte[] chkB = { 48,49,50,51,52,53,54,55,56,57,65,66,67,68,69,70,71,72,
73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,97,98,99,
100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,
115,116,117,118,119,120,121,122,45,95,46,33,126,42,39,40,41,59,
47,63,58,64,38,61,43,36,44};

byte[] b = chkS.getBytes (encoding);
return Arrays.equals (b, chkB);
}

/** Open a connection to the server. */
public void openServer(String server, int port)
throws IOException, UnknownHostException {
if (serverSocket != null)
closeServer();
serverSocket = doConnect (server, port);
try {
serverOutput = new PrintStream(new BufferedOutputStream(
serverSocket.getOutputStream()),
true, encoding);
} catch (UnsupportedEncodingException e) {
throw new InternalError(encoding +"encoding not found");
}
serverInput = new BufferedInputStream(serverSocket.getInputStream());
}

/**
* Return a socket connected to the server, with any
* appropriate options pre-established
*/
protected Socket doConnect (String server, int port)
throws IOException, UnknownHostException {
Socket s;
if (proxy != null) {
if (proxy.type() == Proxy.Type.SOCKS) {
s = (Socket) AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
return new Socket(proxy);
}});
} else if (proxy.type() == Proxy.Type.DIRECT) {
s = createSocket();
} else {
// Still connecting through a proxy
// server & port will be the proxy address and port
s = new Socket(Proxy.NO_PROXY);
}
} else
s = createSocket();
// Instance specific timeouts do have priority, that means
// connectTimeout & readTimeout (-1 means not set)
// Then global default timeouts
// Then no timeout.
if (connectTimeout >= 0) {
s.connect(new InetSocketAddress(server, port), connectTimeout);
} else {
if (defaultConnectTimeout > 0) {
s.connect(new InetSocketAddress(server, port), defaultConnectTimeout);
} else {
s.connect(new InetSocketAddress(server, port));
}
}
if (readTimeout >= 0)
s.setSoTimeout(readTimeout);
else if (defaultSoTimeout > 0) {
s.setSoTimeout(defaultSoTimeout);
}
return s;
}

/**
* The following method, createSocket, is provided to allow the
* https client to override it so that it may use its socket factory
* to create the socket.
*/
protected Socket createSocket() throws IOException {
return new java.net.Socket();
}

protected InetAddress getLocalAddress() throws IOException {
if (serverSocket == null)
throw new IOException("not connected");
return serverSocket.getLocalAddress();
}

/** Close an open connection to the server. */
public void closeServer() throws IOException {
if (! serverIsOpen()) {
return;
}
serverSocket.close();
serverSocket = null;
serverInput = null;
serverOutput = null;
}

/** Return server connection status */
public boolean serverIsOpen() {
return serverSocket != null;
}

/** Create connection with host <i>host</i> on port <i>port</i> */
public NetworkClient(String host, int port) throws IOException {
openServer(host, port);
}

public NetworkClient() {}

public void setConnectTimeout(int timeout) {
connectTimeout = timeout;
}

public int getConnectTimeout() {
return connectTimeout;
}

public void setReadTimeout(int timeout) {
if (serverSocket != null && timeout >= 0) {
try {
serverSocket.setSoTimeout(timeout);
} catch(IOException e) {
// We tried...
}
}
readTimeout = timeout;
}

public int getReadTimeout() {
return readTimeout;
}
}

　

----------------------------------------------------------------------------------------------------------------------------------------------

下面是sun.net.NetworkClient类中的doConnect(String server,int port)方法，具体执行了创建TCP连接的工作

/**

public void openServer(String server, int port) throws IOException {
serverSocket = doConnect(server, port);
try {
serverOutput = new PrintStream(
new BufferedOutputStream(serverSocket.getOutputStream()),
false, encoding);
} catch (UnsupportedEncodingException e) {
throw new InternalError(encoding+" encoding not found");
}
serverSocket.setTcpNoDelay(true);
}

　　

* Return a socket connected to the server, with any appropriate options * pre-established */ protected Socket doConnect(String server, int port) throws IOException, UnknownHostException { Socket s; if (proxy != null) { if (proxy.type() == Proxy.Type.SOCKS) { s = (Socket) AccessController.doPrivileged(new PrivilegedAction() { public Object run() { return new Socket(proxy); } }); } else if (proxy.type() == Proxy.Type.DIRECT) { s = createSocket(); } else { // Still connecting through a proxy // server & port will be the proxy address and port s = new Socket(Proxy.NO_PROXY); } } else s = createSocket(); // Instance specific timeouts do have priority, that means // connectTimeout & readTimeout (-1 means not set) // Then global default timeouts // Then no timeout. if (connectTimeout >= 0) { s.connect(new InetSocketAddress(server, port), connectTimeout); } else { if (defaultConnectTimeout > 0) { s.connect(new InetSocketAddress(server, port), defaultConnectTimeout); } else { s.connect(new InetSocketAddress(server, port)); } } if (readTimeout >= 0) s.setSoTimeout(readTimeout); else if (defaultSoTimeout > 0) { s.setSoTimeout(defaultSoTimeout); } return s; }

(1)final URL url = new URL(str);

final HttpURLConnection conn = (HttpURLConnection)url.openConnection();

.........

.........//对Connection进行一系列的参数设置

final OutputStream outputStream = conn.getOutputStream()

outputStream.write(body.getBytes（“UTF-8”）)；

sun.net.www.protocol.http.HttpURLConnection类当中的getOutputStream()方法

/*
* Allowable input/output sequences:
* [interpreted as POST/PUT]
* - get output, [write output,] get input, [read input]
* - get output, [write output]
* [interpreted as GET]
* - get input, [read input]
* Disallowed:
* - get input, [read input,] get output, [write output]
*/
public synchronized OutputStream getOutputStream() throws IOException
{

try
{
if (!doOutput)
{
throw new ProtocolException("cannot write to a URLConnection" + " if doOutput=false - call setDoOutput(true)");
}

if (method.equals("GET"))
{
method = "POST"; // Backward compatibility
}
if (!"POST".equals(method) && !"PUT".equals(method) && "http".equals(url.getProtocol()))
{
throw new ProtocolException("HTTP method " + method + " doesn't support output");
}

// if there's already an input stream open, throw an exception
if (inputStream != null)
{
throw new ProtocolException("Cannot write output after reading input.");
}

if (!checkReuseConnection())
connect();

/*
* REMIND: This exists to fix the HttpsURLConnection subclass.
* Hotjava needs to run on JDK1.1FCS. Do proper fix in subclass for
* 1.2 and remove this.
*/

if (streaming() && strOutputStream == null)
{
writeRequests();
}
ps = (PrintStream) http.getOutputStream();
if (streaming())
{
if (strOutputStream == null)
{
if (fixedContentLength != -1)
{
strOutputStream = new StreamingOutputStream(ps, fixedContentLength);
}
else if (chunkLength != -1)
{
strOutputStream = new StreamingOutputStream(new ChunkedOutputStream(ps, chunkLength), -1);
}
}
return strOutputStream;
}
else
{
if (poster == null)
{
poster = new PosterOutputStream();
}
return poster;
}
}
catch(RuntimeException e)
{
disconnectInternal();
throw e;
}
catch(IOException e)
{
disconnectInternal();
throw e;
}
}

(2) 调用本类的connect()方法

// overridden in HTTPS subclass
public void connect() throws IOException {
plainConnect();
}

(3) 继续调用本类的plainConnect()方法

connected变量是java.net.URLConnection类当中的变量

/**
* If <code>false</code>, this connection object has not created a
* communications link to the specified URL. If <code>true</code>,
* the communications link has been established.
*/
protected boolean connected = false;

------

关于Cache，应该是个优化的重点

cacheHandler类是java.net.ResponseCache接口的实现类

protected void plainConnect()  throws IOException {
if (connected) {
return;
}
// try to see if request can be served from local cache
if (cacheHandler != null && getUseCaches()) {
try {
URI uri = ParseUtil.toURI(url);
if (uri != null) {
cachedResponse = cacheHandler.get(uri, getRequestMethod(), requests.getHeaders(EXCLUDE_HEADERS));
if ("https".equalsIgnoreCase(uri.getScheme())
&& !(cachedResponse instanceof SecureCacheResponse)) {
cachedResponse = null;
}
if (cachedResponse != null) {
cachedHeaders = mapToMessageHeader(cachedResponse.getHeaders());
cachedInputStream = cachedResponse.getBody();
}
}
} catch (IOException ioex) {
// ignore and commence normal connection
}
if (cachedHeaders != null && cachedInputStream != null) {
connected = true;
return;
} else {
cachedResponse = null;
}
}
try {
/* Try to open connections using the following scheme,
* return on the first one that's successful:
* 1) if (instProxy != null)
*        connect to instProxy; raise exception if failed
* 2) else use system default ProxySelector
* 3) is 2) fails, make direct connection
*/

if (instProxy == null) { // no instance Proxy is set
/**
* Do we have to use a proxy?
*/
ProxySelector sel = (ProxySelector)
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
return ProxySelector.getDefault();
}
});
Proxy p = null;
if (sel != null) {
URI uri = sun.net.www.ParseUtil.toURI(url);
Iterator<Proxy> it = sel.select(uri).iterator();
while (it.hasNext()) {
p = it.next();
try {
if (!failedOnce) {
http = getNewHttpClient(url, p, connectTimeout);
http.setReadTimeout(readTimeout);
} else {
// make sure to construct new connection if first
// attempt failed
http = getNewHttpClient(url, p, connectTimeout, false);
http.setReadTimeout(readTimeout);
}
break;
} catch (IOException ioex) {
if (p != Proxy.NO_PROXY) {
sel.connectFailed(uri, p.address(), ioex);
if (!it.hasNext()) {
// fallback to direct connection
http = getNewHttpClient(url, null, connectTimeout, false);
http.setReadTimeout(readTimeout);
break;
}
} else {
throw ioex;
}
continue;
}
}
} else {
// No proxy selector, create http client with no proxy
if (!failedOnce) {
http = getNewHttpClient(url, null, connectTimeout);
http.setReadTimeout(readTimeout);
} else {
// make sure to construct new connection if first
// attempt failed
http = getNewHttpClient(url, null, connectTimeout, false);
http.setReadTimeout(readTimeout);
}
}
} else {
if (!failedOnce) {
http = getNewHttpClient(url, instProxy, connectTimeout);
http.setReadTimeout(readTimeout);
} else {
// make sure to construct new connection if first
// attempt failed
http = getNewHttpClient(url, instProxy, connectTimeout, false);
http.setReadTimeout(readTimeout);
}
}

ps = (PrintStream)http.getOutputStream();
} catch (IOException e) {
throw e;
}
// constructor to HTTP client calls openserver
connected = true;
}

　　

经过各种纠结判断创建了新的HttpClient对象

在HttpClient对象的构造方法当中

protected HttpClient(URL url, Proxy p, int to) throws IOException {
proxy = (p == null) ? Proxy.NO_PROXY : p;
this.host = url.getHost();
this.url = url;
port = url.getPort();
if (port == -1) {
port = getDefaultPort();
}
setConnectTimeout(to);

// get the cookieHandler if there is any
cookieHandler = (CookieHandler)java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
return CookieHandler.getDefault();
}
});

openServer();
}

出现了openServer()方法,openServer()方法

protected synchronized void openServer() throws IOException {

SecurityManager security = System.getSecurityManager();

if (keepingAlive) { // already opened
if (security != null) {
security.checkConnect(host, port);
}

return;
}

String urlHost = url.getHost().toLowerCase();

if (url.getProtocol().equals("http") ||
url.getProtocol().equals("https") ) {

if ((proxy != null) && (proxy.type() == Proxy.Type.HTTP)) {
sun.net.www.URLConnection.setProxiedHost(host);
if (security != null) {
security.checkConnect(host, port);
}
privilegedOpenServer((InetSocketAddress) proxy.address());
usingProxy = true;
return;
} else {
// make direct connection
if (security != null) {
// redundant?
security.checkConnect(host, port);
}
openServer(host, port);
usingProxy = false;
return;
}

} else {
/* we're opening some other kind of url, most likely an
* ftp url.
*/
if ((proxy != null) && (proxy.type() == Proxy.Type.HTTP)) {
sun.net.www.URLConnection.setProxiedHost(host);
if (security != null) {
security.checkConnect(host, port);
}
privilegedOpenServer((InetSocketAddress) proxy.address());
usingProxy = true;
return;
} else {
// make direct connection
if (security != null) {
// redundant?
security.checkConnect(host, port);
}
super.openServer(host, port);
usingProxy = false;
return;
}
}
}

最终openServer()方法调用了有参数的openServer方法，该方法中调用了doConnect()方法

public void openServer(String server, int port) throws IOException {
serverSocket = doConnect(server, port);
try {
serverOutput = new PrintStream(
new BufferedOutputStream(serverSocket.getOutputStream()),
false, encoding);
} catch (UnsupportedEncodingException e) {
throw new InternalError(encoding+" encoding not found");
}
serverSocket.setTcpNoDelay(true);
}

最终创建了TCP连接。

socket对象获得了getOutputStream输出流被装饰了两次分别称为了有缓存的Buffered 和Print

由于HttpClient类是NetworkClient类的子类，调用的doConnect方法是父类中方法，最终调用的是connect(SocketAddress xxx)方法来建立连接

/**
* Return a socket connected to the server, with any
* appropriate options pre-established
*/
protected Socket doConnect (String server, int port)
throws IOException, UnknownHostException {
Socket s;
if (proxy != null) {
if (proxy.type() == Proxy.Type.SOCKS) {
s = (Socket) AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
return new Socket(proxy);
}});
} else if (proxy.type() == Proxy.Type.DIRECT) {
s = createSocket();
} else {
// Still connecting through a proxy
// server & port will be the proxy address and port
s = new Socket(Proxy.NO_PROXY);
}
} else
s = createSocket();
// Instance specific timeouts do have priority, that means
// connectTimeout & readTimeout (-1 means not set)
// Then global default timeouts
// Then no timeout.
if (connectTimeout >= 0) {
s.connect(new InetSocketAddress(server, port), connectTimeout);
} else {
if (defaultConnectTimeout > 0) {
s.connect(new InetSocketAddress(server, port), defaultConnectTimeout);
} else {
s.connect(new InetSocketAddress(server, port));
}
}
if (readTimeout >= 0)
s.setSoTimeout(readTimeout);
else if (defaultSoTimeout > 0) {
s.setSoTimeout(defaultSoTimeout);
}
return s;
}