Java中如何?自動Host綁定IP

需求：因為測試伺服器有多台，一般都是通過綁定host來訪問某一台測試伺服器，現在就想用代碼來實現綁定host的功能，這樣就省去了修改本機host的步驟。
以下是用代理來實現：

public static HttpURLConnection getConnection(String urlstr, String proxyhost)throws Exception {    URL url = new URL(urlstr);    byte ip[] = new byte[4];    String arr[] = proxyhost.split("\\.");    for (int i = 0; i < 4; i++) {        int tmp = Integer.valueOf(arr[i]);        ip[i] = (byte) tmp;    }    //產生proxy代理對象，因為http底層是socket實現    Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(            InetAddress.getByAddress(ip), 80));    return (HttpURLConnection) url.openConnection(proxy);}public static void main(String[] args) throws Exception {    String url = "http://www.xujsh.com/api/hao123";    String proxyhost = "192.168.119.182";    HttpURLConnection httpUrlConn = getConnection(url, proxyhost);    InputStream in = httpUrlConn.getInputStream();    String response = FileUtil.getContent(in, "UTF-8");    System.out.println(response);}

參考：http://blog.csdn.net/zhongweijian/article/details/7619453
以下是基於HttpClient的實現：

public static void main(String[] args)throws Exception {    HttpHost proxyhost = new HttpHost("192.168.119.182", 80, "http");    DefaultHttpClient httpclient = new DefaultHttpClient();    try {        httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY, proxyhost);        HttpHost targethost = new HttpHost("www.xujsh.com", 80, "http");        HttpGet get = new HttpGet("/api/hao123");                System.out.println("executing request to " + targethost + " via " + proxyhost);        HttpResponse rsp = httpclient.execute(targethost, get);        HttpEntity entity = rsp.getEntity();        System.out.println("----------------------------------------");        System.out.println(rsp.getStatusLine());        Header[] headers = rsp.getAllHeaders();        for (int i = 0; i<headers.length; i++) {            System.out.println(headers[i]);        }        System.out.println("----------------------------------------");        if (entity != null) {            System.out.println(EntityUtils.toString(entity));        }    } finally {        httpclient.getConnectionManager().shutdown();    }}

其實也不難理解，原理大概就是：用戶端發送一個請求給服務端，如果服務端是一個Proxy 伺服器，它就會轉寄用戶端的請求，如果服務端不是一個Proxy 伺服器，
而只是一台普通的應用伺服器，它就是自己來響應這個請求。

其實Proxy 伺服器本身也不是什麼神秘的東西，我們來自己寫一個簡單的Proxy 伺服器。在原生8989連接埠接收用戶端的請求，然後進行轉寄。
服務端：

public class MyProxyServer {    public static void main(String[] args) {        try {            new Thread(new SimpleProxyServer(8989)).start();        } catch (IOException e) {            e.printStackTrace();        }    }}class SimpleProxyServer implements Runnable {    private ServerSocket listenSocket;    public SimpleProxyServer(int port) throws IOException {        this.listenSocket = new ServerSocket(port);    }    public void run() {        for (;;) {            try {                Socket clientSocket = listenSocket.accept();                System.out                        .println("Create a new Thread to handle this connection");                new Thread(new ConnectionHandler(clientSocket)).start();            } catch (IOException e) {                e.printStackTrace();            }        }    }}class ProxyCounter {    static int sendLen = 0;    static int recvLen = 0;    public static void showStatistics() {        System.out.println("sendLen = " + sendLen);        System.out.println("recvLen = " + recvLen);    }}// must close sockets after a transactionclass ConnectionHandler extends ProxyCounter implements Runnable {    private Socket clientSocket;    private Socket serverSocket;    private static final int bufferlen = 1024*1024;    public ConnectionHandler(Socket clientSocket) {        this.clientSocket = clientSocket;    }    public void run() {        // receive request from clientSocket,        // extract hostname,        // create a serverSocket to communicate with the host        // count the bytes sent and received        try {            byte[] buffer = new byte[bufferlen];            int count = 0;            InputStream inFromClient = clientSocket.getInputStream();            count = inFromClient.read(buffer);            String request = new String(buffer, 0, count);            System.out.println("request:\n"+request);            String host = extractHost(request);            System.out.println("host:\n"+host);            // create serverSocket            Socket serverSocket = new Socket(host, 80);            // forward request to internet host            OutputStream outToHost = serverSocket.getOutputStream();            outToHost.write(buffer, 0, count);            outToHost.flush();            sendLen += count;            showStatistics();            // forward response from internet host to client            InputStream inFromHost = serverSocket.getInputStream();            OutputStream outToClient = clientSocket.getOutputStream();            while (true) {                count = inFromHost.read(buffer);                System.out.println("count:"+count);                if (count < 0)                    break;                outToClient.write(buffer, 0, count);                outToClient.flush();                recvLen += count;                showStatistics();            }        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                if(clientSocket != null)clientSocket.close();                if(serverSocket != null)serverSocket.close();            } catch (IOException e) {                e.printStackTrace();            }        }    }    private String extractHost(String request) {        int start = request.indexOf("Host: ") + 6;        int end = request.indexOf('\n', start);        String host = request.substring(start, end - 1);        return host;    }}

參考：http://my.oschina.net/u/158589/blog/64643
用戶端測試：

public class MyProxyClient {    public static void main(String[] args) throws Exception {        Socket socket = new Socket("localhost",8989);        OutputStream out = socket.getOutputStream();        out.write("GET / HTTP/1.1\nHost: www.baidu.com \n\n".getBytes());        out.flush();        InputStream in = socket.getInputStream();        byte[] arr = FileUtil.readAsByteArray(in);        System.out.println(new String(arr));        socket.close();    }}

關於javaProxy 伺服器設定的，參考：http://blog.csdn.net/mebusw/article/details/6372714