urlchat.java

java3D game engine design of the source [three-dimensionalvirtualrealitynetworkprogram] - "virtual

// URLChat.java
// Andrew Davison, June 2003, [e-mail]
/*
  A Chat client that uses a servlet as the server. Messages 
  are sent as arguments to the servlet's URL.
  Responses are text based (often just "ok" or "no").

  The client obtains a cookie when it first connects, and
  uses that in subsequent communication (along with the client's
  name) as a simple way of confirming its identity. 
  The cookie contains a user ID (uid).

  Client Messages:
    * ChatServlet?cmd=hi&name=??         
        // hi message to ask to join the chat group. The
           server returns a uid cookie, or rejects the client.

    * ChatServlet?cmd=bye&name=?? + uid cookie
        // bye message to signal client departure

    * ChatServlet?cmd=who
       // the "who" message; no name or cookie required.
          Returns a list of who is logged on currently

    * ChatServlet?cmd=msg&name=??&msg=?? + uid cookie
        // add a message to the server's chat messages list


  There is a separate thread, URLChatWatcher which periodically
  sends a "read" message to the servlet:
      ChatServlet?cmd=read&name=??  + uid cookie
        // this retrieves all the visible messages stored on
           the server since the last read
*/

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import java.util.*;


public class URLChat extends JFrame implements ActionListener
{
  private static final String SERVER = "http://localhost:8080/servlet/ChatServlet";
    // arguments are added to this to vary the communication with ChatServlet

  private String userName;  // for this client
  private String cookieStr = null;
  
  private JTextArea jtaMesgs;   // GUI components
  private JTextField jtfMsg;
  private JButton jbWho;


  public URLChat(String nm)
  {
     super( "URL Chat Client for "+ nm);

     userName = nm;
     initializeGUI();

     // set the properties used for URL timeouts (in ms)
     Properties props = System.getProperties();
     props.put("sun.net.client.defaultConnectTimeout", "2000");
     props.put("sun.net.client.defaultReadTimeout", "2000");
     System.setProperties(props);

     sayHi();
     new URLChatWatcher(this, userName, cookieStr).start();    
         // start polling the server, getting new chat messages
         // which are written into the jtaMesgs text area

     addWindowListener( new WindowAdapter() {
       public void windowClosing(WindowEvent e)
       { sayBye(); }
     });

     setSize(300,450);
     show();
  } // end of URLChat();


  private void initializeGUI()
  /* Text area in center, and controls below.
     Controls:
         - textfield for entering messages
         - a "Who" button
  */
  {
    Container c = getContentPane();
    c.setLayout( new BorderLayout() );

    jtaMesgs = new JTextArea(7, 7);
    jtaMesgs.setEditable(false);
    JScrollPane jsp = new JScrollPane( jtaMesgs);
    c.add( jsp, "Center");

    JLabel jlMsg = new JLabel("Message: ");
    jtfMsg = new JTextField(15);
    jtfMsg.addActionListener(this);    // pressing enter triggers sending of name/score

    jbWho = new JButton("Who");
    jbWho.addActionListener(this);

    JPanel p1 = new JPanel( new FlowLayout() );
    p1.add(jlMsg); p1.add(jtfMsg);

    JPanel p2 = new JPanel( new FlowLayout() );
    p2.add(jbWho);

    JPanel p = new JPanel();
    p.setLayout( new BoxLayout(p, BoxLayout.Y_AXIS));
    p.add(p1); p.add(p2);

    c.add(p, "South");

  }  // end of initializeGUI()



  private void sayHi()
  /* Message format: ChatServlet?cmd=hi&name=??         
     The client asks to join the chat group. 
     The server returns a uid cookie as a header field, 
     or rejects the client. A rejection causes the client to exit.
     The textual response can be "ok" or "no".
  */
  {
    try {
      URL url  = new URL(SERVER + "?cmd=hi&name=" +  
							URLEncoder.encode(userName, "UTF-8") );

      URLConnection conn = url.openConnection();
      cookieStr = conn.getHeaderField("Set-Cookie");  // get the cookie

      System.out.println("Received cookie: " + cookieStr);
      if (cookieStr != null) {
        int index = cookieStr.indexOf(";"); 
        if (index != -1) 
          cookieStr = cookieStr.substring(0, index);  // strip away extras
      }

	  BufferedReader br = new BufferedReader(
              new InputStreamReader( conn.getInputStream() ));	
      String response = br.readLine().trim();
      br.close();

      if (response.equals("ok") && (cookieStr != null))
        showMsg("Server Login Successful\n");
      else { 
        System.out.println("Server Rejected Login"); 
        System.exit(0);
      }
    }
    catch(Exception e)
    { System.out.println(e);  
      System.exit(0);
    }
  }  // end of sayHi()



  private void sayBye()
  /* ChatServlet?cmd=bye&name=?? + uid cookie
     The bye message signals the client's departure to the server.
     The response will be "ok" or "no", but the client
     exits whatever the response.
  */
  {
    try {
      URL url  = new URL(SERVER + "?cmd=bye&name=" + 
							URLEncoder.encode(userName, "UTF-8") );
      URLConnection conn = url.openConnection();
      conn.setRequestProperty("Cookie", cookieStr); 

	  BufferedReader br = new BufferedReader(
              new InputStreamReader( conn.getInputStream() ));	
      String response = br.readLine().trim();
      br.close();

      if (response.equals("ok"))
        System.out.println("Server Logout Successful");
      else // assume "no"
        System.out.println("Server Rejected Logout"); 
    }
    catch(Exception e)
    {  System.out.println( e );  }

    System.exit(0); 
  } // end of sayBye()


   public void actionPerformed(ActionEvent e)
   /* Either a message is to be sent or the "Who"
      button has been pressed. */
   { if (e.getSource() == jbWho)
       askWho();
     else if (e.getSource() == jtfMsg)
       sendMessage();
   } // end of actionPerformed()



  private void askWho()
  /*  Message format: ChatServlet?cmd=who
      The message does not require a name argument or a cookie.
      The response is a list of who is currently logged on,
      or "no". The list is displayed in the jtsMesgs text area.
  */
  { try {
      URL url  = new URL(SERVER + "?cmd=who" );

	  BufferedReader br = new BufferedReader(
              new InputStreamReader( url.openStream() ));

      String line;
      StringBuffer resp = new StringBuffer();
      while ((line = br.readLine()) != null)   // multiple lines sent back
        resp.append(line+"\n");
      br.close();

      String response = resp.toString();
      if (response.equals("no"))
        showMsg("Server Rejected Who Request\n");
      else // assume there is a list to display
        showMsg(response); 
    }
    catch(Exception e)
    { showMsg("Servlet Error. Who button not processed\n");
      System.out.println(e);  
    }
  }  // end of askWho()


  private void sendMessage()
  /* Check if the user has supplied a message, then
     send it to the servlet. */
  {
    String msg = jtfMsg.getText().trim();
    // System.out.println("'"+msg+"'");

    if (msg.equals(""))
      JOptionPane.showMessageDialog( null, 
           "No message entered", "Send Message Error", 
			JOptionPane.ERROR_MESSAGE);
    else {
      sendURLMessage(msg);
      // showMsg("Sent: " + msg + "\n");
    }
  }  // end of sendMessage()



  private void sendURLMessage(String msg)
  /* Message format: 
        ChatServlet?cmd=msg&name=??&msg=?? + uid cookie

     The message is added to the servlet's list.
     The response is "ok" or "no".
  */
  { try {
      URL url  = new URL(SERVER + "?cmd=msg&name=" +  
							URLEncoder.encode(userName, "UTF-8") +
                            "&msg=" + 
							URLEncoder.encode(msg, "UTF-8") );

      URLConnection conn = url.openConnection();
      conn.setRequestProperty("Cookie", cookieStr); 

	  BufferedReader br = new BufferedReader(
              new InputStreamReader( conn.getInputStream() ));	
      String response = br.readLine().trim();
      br.close();

      if (!response.equals("ok"))
        showMsg("Message Send Rejected\n");
      else // display message immediately
        showMsg("(" + userName + ") " + msg + "\n");
    }
    catch(Exception e)
    { showMsg("Servlet Error. Did not send: " + msg + "\n");
      System.out.println(e);  
    }
  }  // end of sendURLMessage()



  synchronized public void showMsg(String msg)
  /* Synchronized since this method can be called by this
     object and the URLChatWatcher thread. */
  { jtaMesgs.append(msg);  }


  // ------------------------------------

  public static void main(String args[]) 
  { if (args.length != 1) {
       System.out.println("usage:  java URLChat <your userName>");
       System.exit(0);
     }
     new URLChat(args[0]);  
  }

} // end of URLChat class