webproxyserver.java

Icarnegie university SSD8电子书和全部练习答案

import java.io.*; 
import java.net.*; 
import java.util.StringTokenizer; 

/** 
 * A Web proxy server which is both a client and a server at the same time. 
 *  @author Li Zhiyu
 */ 
 
public class WebProxyServer { 

  public WebProxyServer() throws Exception { 
    /* the server socket */ 
    ServerSocket serSk = new ServerSocket(8080); 

    /* the counter of clients */ 
    int counter = 1; 
    while (true) { 
      Socket cliSk = serSk.accept(); 
      System.out.println("Accepting Client " + counter + "'s Connection...\n"); 

      /* a thread for a client */ 
      ServerThread st = new ServerThread(cliSk, counter++); 
      st.start(); 
    } 
  } 

  class ServerThread extends Thread { 

    /* a client socket */ 
    private Socket sk; 
    /* the counter of clients */ 
    private int counter; 

    ServerThread(Socket sk, int counter) { 
      this.sk = sk; 
      this.counter = counter; 
    } 

    public void run() { 
      /* reader and writer */ 
      BufferedReader inFromClient = null; 
      DataInputStream inFromServer = null; 
      DataOutputStream outToClient = null; 
      DataOutputStream outToServer = null; 
      /* response the request */ 
      try { 
        while (true) { 
          /* Reader and writer between proxy server and client */ 
          inFromClient = new BufferedReader(new InputStreamReader(sk.getInputStream())); 
          outToClient = new DataOutputStream(sk.getOutputStream()); 
          System.out.println("Waiting for Client " + counter + "\'s command..."); 
          String cmd = inFromClient.readLine(); 
          System.out.println("The Client " + counter + " request for: " + cmd); 

          /* 
           * Process the command from client and identify the method 
           * and address. If command error, write the error response 
           * and break.           
           */ 
 
          StringTokenizer token = new StringTokenizer(cmd); 
 
          if (token.countTokens() < 2) { 
            System.out.println("Command style error!"); 
            outToClient.writeBytes("HTTP/1.1 400 Bad Request\n\r"); 
            break; 
          } 
          else {
            String method = token.nextToken(); 
            String url = token.nextToken(); 
            if (!method.equals("GET")) { 
              System.out.println("method error!"); 
              System.out.println("HTTP/1.1 400 Bad Request\n\r"); 
              break; 
 
            } 
 
            if (!url.toUpperCase().startsWith("HTTP://")) { 
              System.out.println("url error!"); 
              System.out.println("HTTP/1.1 400 Bad Request\n\r"); 
              break; 
            } 

            /* 
             * process the file name and make sure the server name, 
             * the file path and the number of port. 
             */ 
            int port = 0; 
            int strIndex = 0; 
      
            String serverName = ""; 
            String portToString = ""; 
            String filePath = ""; 
 
            url = url.substring(7); 
            strIndex = url.indexOf("/"); 
            serverName = url.substring(0, url.indexOf("/")); 
            filePath = url.substring(url.indexOf("/")); 
 
            if (serverName.contains(":")) { 
              strIndex = serverName.indexOf(":"); 
              portToString = serverName.substring(strIndex + 1); 
              serverName = serverName.substring(0, strIndex); 
            } 
            else { 
              portToString = "80"; 

            } 
            port = Integer.parseInt(portToString); 
 
            /* 
             * Response the right format request. Identify the file 
             * tpye and write it to the client
             */ 
 
            System.out.println(serverName); 
            System.out.println(port); 
            System.out.println(filePath); 
            System.out.println(url); 
            System.out.println("Now respond the Client " + counter 
                + "\'s request..."); 

            /* the client socket */ 
            Socket clientSocket = new Socket(serverName, port); 
 
            /* Reader and writer between proxy server and server */ 
            inFromServer = new DataInputStream(clientSocket.getInputStream()); 
 
            outToServer = new DataOutputStream(clientSocket.getOutputStream()); 

            outToServer.writeBytes("GET " + filePath + " HTTP/1.0\r\n\r\n"); 
 
            /* read from server and write to client */ 
 
            String response = inFromServer.readLine(); 
            while (!response.equals("")) { 
              response = inFromServer.readLine(); 
            } 
            
            byte[] bytes = new byte[1024]; 
            int size = 0;           
            while ((size = inFromServer.read(bytes, 0, 1024)) != -1) { 
              outToClient.write(bytes, 0, size); 
            }   break; 
          } 
        } 
      } 
      catch (Exception e) { 
        e.printStackTrace(); 
      } 
      finally { 
         // Close the reader, writer and client socket.         
        System.out.println("Closing Client " + counter + "\'s Connection...\n"); 
        try { 
          if (inFromClient != null) 
            inFromClient.close(); 
 
          if (outToClient != null) 
            outToClient.close(); 
 
          if (inFromServer != null) 
            inFromServer.close(); 
 
          if (outToServer != null) 
            outToServer.close(); 
 
          if (sk != null) 
            sk.close(); 
        } 
        catch (IOException e) { 
        } 
      } 
    } 
  } 
 
  public static void main(String[] args) { 
    try { 
      WebProxyServer pServer = new WebProxyServer(); 
    } 
    catch (Exception e) { 
         e.printStackTrace(); 
 
    } 

  } 

}