简单的HTTP代理服务器实现

package proxy2;

import java.io.*;
import java.net.*;

public class MyHttpProxy extends Thread {
static public int CONNECT_RETRIES = 5; // 尝试与目标主机连接次数
static public int CONNECT_PAUSE = 5; // 每次建立连接的间隔时间
static public int TIMEOUT = 50; // 每次尝试连接的最大时间
static public int BUFSIZ = 1024; // 缓冲区最大字节数
static public boolean logging = false; // 是否记录日志
static public OutputStream log_S = null; // 日志输出流
static public OutputStream log_C = null; // 日志输出流
static public String LOGFILENAME_S = "log_S.txt";
static public String LOGFILENAME_C = "log_C.txt";
// 与客户端相连的Socket
protected Socket csocket;

public MyHttpProxy(Socket cs) {
csocket = cs;
start();
}

public void writeLog(int c, boolean browser) throws IOException {
if (browser)
log_C.write((char) c);
else
log_S.write((char) c);
}

public void writeLog(byte[] bytes, int offset, int len, boolean browser)
throws IOException {
for (int i = 0; i < len; i++)
writeLog((int) bytes[offset + i], browser);
}

public void run() {
String buffer = ""; // 读取请求头
String URL = ""; // 读取请求URL
String host = ""; // 读取目标主机host
int port = 80; // 默认端口80
Socket ssocket = null;
// cis为客户端输入流，sis为目标主机输入流
InputStream cis = null, sis = null;
// cos为客户端输出流，sos为目标主机输出流
OutputStream cos = null, sos = null;
try {
csocket.setSoTimeout(TIMEOUT);
cis = csocket.getInputStream();
cos = csocket.getOutputStream();
while (true) {
int c = cis.read();// ?此处好多timeout异常。
if (c == -1)
break; // -1为结尾标志
if (c == '\r' || c == '\n')
break;// 读入第一行数据
buffer = buffer + (char) c;
if (logging)
writeLog(c, true);
}
// 抽取URL
URL = getRequestURL(buffer);

int n;
// 抽取host
n = URL.indexOf("//");
if (n != -1)
host = URL.substring(n + 2); // www.baidu.com/
n = host.indexOf('/');
if (n != -1)
host = host.substring(0, n);// www.baidu.com

// 分析可能存在的端口号
n = host.indexOf(':');
if (n != -1) {
port = Integer.parseInt(host.substring(n + 1));
host = host.substring(0, n);
}
int retry = CONNECT_RETRIES;
while (retry-- != 0) {
try {
ssocket = new Socket(host, port); // 尝试建立与目标主机的连接
break;
} catch (Exception e) {
}
// 等待
Thread.sleep(CONNECT_PAUSE);
}
if (ssocket != null) {
ssocket.setSoTimeout(TIMEOUT);
sis = ssocket.getInputStream();
sos = ssocket.getOutputStream();
sos.write(buffer.getBytes()); // 将请求头写入
pipe(cis, sis, sos, cos); // 建立通信管道
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (csocket != null)
csocket.close();
if (cis != null)
cis.close();
if (cos != null)
cos.close();
} catch (Exception e1) {
System.out.println("\nClient Socket Closed Exception:");
e1.printStackTrace();
}
try {
if (ssocket != null)
ssocket.close();
if (sis != null)
sis.close();
if (sos != null)
sos.close();
} catch (Exception e2) {
System.out.println("\nServer Socket Closed Exception:");
e2.printStackTrace();
}
}
}

public String getRequestURL(String buffer) {
String[] tokens = buffer.split(" ");
String URL = "";
for (int index = 0; index < tokens.length; index++) {
if (tokens[index].startsWith("http://")) {
URL = tokens[index];
break;
}
}
return URL;
}

public void pipe(InputStream cis, InputStream sis, OutputStream sos,
OutputStream cos) {
try {
int length;
byte bytes[] = new byte[BUFSIZ];
while (true) {
try {
if ((length = cis.read(bytes)) > 0) {
sos.write(bytes, 0, length);
if (logging)
writeLog(bytes, 0, length, true);
} else if (length < 0)
break;
} catch (SocketTimeoutException e) {
} catch (InterruptedIOException e) {
System.out.println("\nRequest Exception:");
e.printStackTrace();
}
try {
if ((length = sis.read(bytes)) > 0) {
cos.write(bytes, 0, length);
if (logging)
writeLog(bytes, 0, length, false);
} else if (length < 0)
break;
} catch (SocketTimeoutException e) {
} catch (InterruptedIOException e) {
System.out.println("\nResponse Exception:");
e.printStackTrace();
}
}
} catch (Exception e0) {
System.out.println("Pipe异常:" + e0);
}
}

public static void startProxy(int port, Class clobj) {
try {
ServerSocket ssock = new ServerSocket(port);
while (true) {
Class[] sarg = new Class[1];
Object[] arg = new Object[1];
sarg[0] = Socket.class;
try {
java.lang.reflect.Constructor cons = clobj
.getDeclaredConstructor(sarg);
arg[0] = ssock.accept();//当某些客户机与serverSocket连接时，创建一个新的套接字，称为socket
cons.newInstance(arg); // 创建HttpProxy或其派生类的实例
} catch (Exception e) {
Socket esock = (Socket) arg[0];
try {
esock.close();
} catch (Exception ec) {
}
}
}
} catch (IOException e) {
System.out.println("\nStartProxy Exception:");
e.printStackTrace();
}
}

// 测试用的简单main方法
static public void main(String args[]) throws FileNotFoundException {
System.out.println("在端口808启动代理服务器\n");
OutputStream file_S = new FileOutputStream(new File(LOGFILENAME_S));
OutputStream file_C = new FileOutputStream(new File(LOGFILENAME_C));
MyHttpProxy.log_S = file_S;
MyHttpProxy.log_C = file_C;
MyHttpProxy.logging = true;
MyHttpProxy.startProxy(808, MyHttpProxy.class);
}

}