talkapplet.java

java网络高级编程的配套源码,java网络高级编程为清华出版社出版.

/*源程序清单5-22*/

import java.net.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import com.borland.jbcl.layout.*;
import java.io.*;
import java.util.*;

public class TalkApplet extends JApplet implements Runnable
{
  boolean isStandalone = false;
  Label userInfo = new Label();
  TextField userText = new TextField();
  Label label1 = new Label();
  TextArea messageText = new TextArea();
  Button sendButton = new Button();
  java.awt.List userList = new java.awt.List();

  URL chatURL;
  URLConnection connect;
  //用于标识用户是否登录
  boolean loggedin=false;
  String username;
  Thread pollThread=null;
  PaneLayout paneLayout1 = new PaneLayout();


  /**Get a parameter value*/
  public String getParameter(String key, String def)
  {
    return isStandalone ? System.getProperty(key, def) :
      (getParameter(key) != null ? getParameter(key) : def);
  }

  /**Construct the applet*/
  public TalkApplet()
  {
  }

  /**Initialize the applet*/
  public void init()
  {
    try
    {
      jbInit();
    }
    catch(Exception e)
    {
      e.printStackTrace();
    }
  }
  /**Component initialization*/
  private void jbInit() throws Exception {
    if(pollThread!=null)
      return;
    userInfo.setText("请输入用户名（请不要超过10个字符）：");
    this.setSize(new Dimension(400,300));
    this.getContentPane().setLayout(paneLayout1);
    label1.setText("聊天内容：");
    messageText.setEditable(false);
    sendButton.setLabel("发送");
    sendButton.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        sendButton_actionPerformed(e);
      }
    });
    userText.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(ActionEvent e) {
        userText_actionPerformed(e);
      }
    });
    this.getContentPane().add(userInfo, new PaneConstraints("userInfo", "userInfo", PaneConstraints.ROOT, 1.0f));
    this.getContentPane().add(userText, new PaneConstraints("userText", "userInfo", PaneConstraints.BOTTOM, 0.9166667f));
    this.getContentPane().add(messageText, new PaneConstraints("messageText", "userText", PaneConstraints.BOTTOM, 0.90181816f));
    this.getContentPane().add(userList, new PaneConstraints("userList", "messageText", PaneConstraints.TOP, 0.24193548f));
    this.getContentPane().add(sendButton, new PaneConstraints("sendButton", "userList", PaneConstraints.LEFT, 0.6125f));
    this.getContentPane().add(label1, new PaneConstraints("label1", "sendButton", PaneConstraints.BOTTOM, 0.6f));
    chatURL=getCodeBase();
    int currPriority=Thread.currentThread().getPriority();
    int newPriority=currPriority==Thread.MIN_PRIORITY?Thread.MIN_PRIORITY:currPriority-1;
    pollThread=new Thread(this,"talkPoll");
    pollThread.setDaemon(true);
    pollThread.setPriority(newPriority);
    pollThread.start();
  }

  /**Get Applet information*/
  public String getAppletInfo()
  {
    return "Applet Information";
  }
  /**Get parameter info*/
  public String[][] getParameterInfo()
  {
    return null;
  }

  public synchronized void start()
  {
    if(!isLoggedin()&&username!=null)
      login();
    if(pollThread!=null&&pollThread.isAlive())
    {
      pollThread.resume();
    }
    else
    {
      pollThread=new Thread(this,"talkPoll");
      pollThread.setDaemon(true);
      pollThread.start();
    }
  }
  //当Applet在浏览器中不可见时，就挂起线程pollthread,并退出"聊天室"
  public synchronized void stop()
  {
    if (pollThread.isAlive())
    {
      pollThread.suspend();
    }
    logout();
  }

  public synchronized void destroy()
  {
    if (pollThread != null && pollThread.isAlive())
    {
       pollThread.stop();
       pollThread = null;
     }
     logout();
  }

  //每隔3秒从服务器中取别的用户输入的信息和加入聊天室的用户
  public void run()
  {
    while (!Thread.interrupted())
    {
	//若用户已经登陆，则不时的取回别的用户输入的信息
	//和机如的的用户名
	if (isLoggedin())
	{
	  pollList();
	  poll();
	}
	//若没有用户登陆，则取回正在聊天室中的用户
	else
	{
	  pollList();
	}
	try
	{
	  //睡眠3秒钟
	  Thread.sleep(1000*3);
	}
	catch (InterruptedException e)
	{
	}
      }
    }

  //登陆到服务器
  private void login()
  {
     if (username ==null) return;
     String queryString = "chatservlet?mode=login&user="+URLEncoder.encode(username);
     //与服务器通信
     try
     {
	connect = (new URL(chatURL,queryString)).openConnection();
	connect.setDefaultUseCaches(false);
	connect.setUseCaches(false);
	connect.setDoInput(true);
	connect.setDoOutput(false);
	connect.connect();
	DataInputStream in = new DataInputStream(connect.getInputStream());
	String response = in.readLine();
	if (response.startsWith("+"))
	{
	  //标识用户已经登陆
	  setLoggedin(true);
	  showStatus("登录用户名：" + username);
	  //提示用户输入信息
	  userInfo.setText("请输入你需要发送的信息:");
	  repaint();
	}
	else
	{
	  showStatus("Error logging in " + response);
	  System.err.println("Error logging in " + response);
	}
    }
    catch (MalformedURLException e2)
    {
	System.err.println("MalformedURLException logging in!");
	e2.printStackTrace(System.err);
	showStatus("Error logging in!");
    }
    catch (IOException e1)
    {
	System.err.println("IOException logging in!");
	e1.printStackTrace(System.err);
	showStatus("Error logging in!");
    }
  }

	//退出聊天室
  private void logout()
  {
    if (!isLoggedin() || username ==null)
    {
	return;
    }
    String queryString = "chatservlet?mode=logout&username=" +URLEncoder.encode(username);
    //与服务器通信
    try
    {
	connect = (new URL(chatURL,queryString)).openConnection();
	connect.setUseCaches(false);
	connect.setDoInput(true);
	connect.setDoOutput(false);
	connect.connect();
	DataInputStream in = new DataInputStream(connect.getInputStream());
	String response = in.readLine();
	if (response.startsWith("+"))
	{
	  //标识用户已经退出聊天室
	  setLoggedin(false);
  	  showStatus(username + "离开聊天室！");
	}
	else
	{
	  showStatus("Error logging out" + response);
	  System.err.println("Error logging out" + response);
	}
    }
    catch (MalformedURLException e2)
    {
	System.err.println("MalformedURLException logging out!");
	e2.printStackTrace(System.err);
	showStatus("Error logging out!");
    }
    catch (IOException e1)
    {
	System.err.println("IOException logging out!");
	e1.printStackTrace(System.err);
	showStatus("Error logging out!");
    }
   }

  //发送用户输入的信息
  private void send()
  {
    String message = userText.getText();
    //用户输入空字符串不发送
    if (message.equals(""))
    {
      return;
    }
    //清除用户在Applet中输入的内容
    userText.setText("");
    showStatus("发送信息！");
    String queryString = "chatservlet?mode=send&user="+URLEncoder.encode(username);
    queryString = queryString + "&message="+URLEncoder.encode(message);
    try
    {
      connect = (new URL(chatURL,queryString)).openConnection();
      connect.setUseCaches(false);
      connect.setDoInput(true);
      connect.setDoOutput(false);
      connect.connect();
      DataInputStream in = new DataInputStream(connect.getInputStream());
      String response = in.readLine();
      if (response.startsWith("+"))
      {
    	showStatus("信息发送出去了");
       }
      else
      {
	showStatus("发送信息错误 " + response);
	System.err.println("Error sending message " + response);
	}
    }
    catch (MalformedURLException e2)
    {
      System.err.println("MalformedURLException logging in!");
      e2.printStackTrace(System.err);
      showStatus("Error logging in!");
     }
    catch (IOException e1)
    {
	System.err.println("IOException logging in!");
	e1.printStackTrace(System.err);
	showStatus("Error logging in!");
    }
  }

  //返回所有用户输入的信息
  private void poll()
  {
    String queryString = "chatservlet?mode=poll&user=" +URLEncoder.encode(username);
    try
    {
	DataInputStream in = new DataInputStream(
	new URL(chatURL,queryString).openStream());
	String nextLine = in.readLine();
	if (!nextLine.startsWith("+"))
	{
	  showStatus("Error getting messages from server!");
	  System.err.println("Error getting messages from server!");
	  return;
	}
	nextLine = in.readLine();
	while (nextLine != null && !nextLine.equals("."))
	{
	  System.err.println(nextLine);
	  messageText.appendText(nextLine + "\r\n");
	  repaint();
	  nextLine = in.readLine();
	}
    }
    catch (IOException e)
    {
	System.err.println("IOException poll!");
	e.printStackTrace(System.err);
    }
  }

  //返回正在聊天室中的用户
  private void pollList()
  {
	String queryString = "chatservlet?mode=list";
	Vector users = new Vector();
	try
 	{
	  URL listURL = new URL(chatURL,queryString);
	  URLConnection listConn = listURL.openConnection();
	  listConn.setDefaultUseCaches(false);
	  listConn.setUseCaches(false);
	  listConn.connect();
	  DataInputStream in = new DataInputStream(
	  listConn.getInputStream());
	  String nextLine = in.readLine();
	  if (!nextLine.startsWith("+"))
	  {
	    showStatus("Error getting userlist from server!");
	    return;
	  }
	  nextLine = in.readLine();
	  while (nextLine != null && !nextLine.equals("."))
	  {
	    users.addElement(nextLine);
	    nextLine = in.readLine();
	   }
	   //清除旧的用户表，加入新的
	   if (!users.isEmpty())
	   {
	     userList.clear();
            int size = users.size();
	     for (int I=0;I<size ;I++ )
             {
		userList.addItem((String)users.elementAt(I));
	     }
	    }
	    else
	    {
		userList.clear();
		userList.addItem("None logged in!");
	    }
	    repaint();
	}
	catch (IOException e)
	{
	  System.err.println("IOException poll!");
	  e.printStackTrace(System.err);
	  showStatus("Error Checking Message!");
	}
  }

  //判断用户是否已经登陆到聊天室
  public boolean isLoggedin()
  {
    return loggedin;
  }

  //设置用户是否登陆的状态
  protected void setLoggedin(boolean newval)
  {
    loggedin = newval;
  }

  void sendButton_actionPerformed(ActionEvent e)
  {
    sendText();
  }

  void sendText()
  {
    if (isLoggedin())
    {
   	send();
    }
    else
    {
	username = userText.getText();
	if (username.length()>10)
	{
  	  showStatus("请不要超过10个字符！");
	}
	else
	{
	  userText.setText("");
	  login();
	}
      }
  }

  void userText_actionPerformed(ActionEvent e)
  {
    sendText();
  }
}