chatservlet.java~1~

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.

/*程序清单5-23*/

package Chat;

import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
import java.util.*;

public class  ChatServlet extends HttpServlet implements Runnable
{
  //用于保存用户的聊天内容
  private UsersList users = new UsersList();
  //保存用户的输入信息
  private MessageText message;
  //缺省的聊天页面
  private final static String defaultStartPage ="/chat/chatapplet.html";
  private Thread thread;
  //用户超过5分钟没有相应，服务器认为已经退出
  final int TIMEOUT = 5*60*1000;

  public void init(ServletConfig config) throws ServletException
  {
    super.init(config);
    //创建和启动线程
    int currPriority = 0;
    currPriority=Thread.currentThread().getPriority();
    int newPriority = 0;
    ewPriority = currPriority == Thread.MIN_PRIORITY? Thread.MIN_PRIORITY:currPriority-1;
    thread = new Thread(this,"ChatReaper");
    thread.setDaemon(true);
    thread.setPriority(newPriority);
    thread.start();
    return;
  }

  public void destroy()
  {
    super.destroy();
    if (thread !=null && thread.isAlive())
    {
      thread.stop();
    }
    return;
  }

  public void service(HttpServletRequest req,HttpServletResponse res)
 	throws IOException,ServletException
  {
    //user保存用户名；mode保存用户命令；usermsg保存用户的输入信息
    String user,mode,usermsg;
    //若用户在请求中没有指定起始页，则缺省就是在初始化参数中设定的
    if (req.getQueryString() == null)
    {
	if (getInitParameter("startpage") == null)
	{
  	  res.sendRedirect(defaultStartpage);
	}
	res.sendRedirect(getInitParameter("startpage"));
	return;
    }
    mode = req.getParameter("mode");
    user = req.getParameter("user");
    if (mode == null)
    {
      sendError(res,"Mode not set!");
      return;
    }
    if (user == null && !mode.equals("list"))
    {
      sendError(res,"User not set!");
      return;
      }
    if (mode.equals("login"))
    {
      if (users.exists(user))
      {
	sendError(res,"User exists!");
	return;
	}
      if (! users.add(user))
      {
	sendError(res,"Error adding user!");
	return;
	}
      users.addMessage(new MessageText("Chat",user+" 加入聊天！"));
      log(user +"登录进来!");
      sendResp(res,"User logged in!");
      return;
      }
      else if (mode.equals("logout"))
      {
	if (! users.exists(user))
	{
	  sendError(res,"用户不存在！");
	  return;
	}
	if (! users.drop(user))
	{
	  sendError(res,"Error dropping user!");
	  return;
	}
	users.addMessage(new MessageText("Chat",user + " has logged out!"));
	log("The user " + user + "logged out!");
	sendResq(res,"User logged out!");
	return;
	}
      else if (mode.equals("poll"))
      {
	if (!users.exists(user))
	{
	  sendError(res,"Invalid Error!");
	  return;
	}
	returnMessages(res,users.getMessages(user));
	users.resetUser(user);
	return;
      }
      else if (mode.equals("send"))
      {
	usermsg = req.getParameter("message");
	if (usermsg == null)
	{
	  sendError(res,"Message not set for send!");
	  return;
	}
	users.addMessage(new MessageText(user,usermsg));
	sendResp(res,"Message Added!");
	return;
      }
      else if (mode.equals("list"))
      {
	returnUserList(res);
	return;
      }
      else
      {
	sendError(res,"Invalid Mode!");
	return;
      }
    }

  //Servlet的线程完成时讲超时的用户退出聊天室
  public void run()
  {
    while (! Threaed.interrupted())
    {
      Enumeration inactive = users.inactive(TIMEOUT);
      while (inactive.hadMoreElements())
      {
	String user = (String)inactive.nextElement();
	users.drop(user);
	users.addMessage(new MessageText("Chat",user + " has timed out!"));
	users.addMessage(new MessageText("Chat",user + " has been dropped from the chat!"));
	log("User " + user + " timed out. Dropped from the chat!");
	}
      try
      {
	Thread.sleep(TIMEOUT);
      }
      catch (InterruptedException e)
      {
        System.out.println(e.toString());
      }
     }
  }

  //向用户发送出错信息
  protected void sendError(HttpServletResponse res,String error)
  {
    try
    {
	PrintStream pout = new PrintStream(res.getOutputStream());
	pout.print("-ERR " + error + "\r\n");
	pout.flush();
	pout.close();
    }
    catch (IOException e)
    {
      System.out.println(e.toString());
    }
  }

  //向用户发送出错信息
  protected void sendResq(HttpServletResponse res,String resp)
  {
  	try
	{
		res.setDateHeader("Expires",System.currentTimeMillis());
		PrintStream pout = new PrintStream(res.getOutputStream());
		pout.print("+OK " + resq + "\r\n");
		pout.flush();
		pout.close();
	}
	catch (IOException e)
	{
          System.out.println(e.toString());
	}
}

  //向用户发送信息
  protected void returnMessages(HttpServletResponse res,Enumeration messagelist)
  {
	try
	{
	  res.setDateHeader("Expires",System.currentTimeMillis());
	  PrintStream pout = new PrintStream(res.getOutputStream());
	  pout.print("+OK\r\n");
	  while (messagelist.hadMoreElements())
	  {
		MessageText message = (MessageText) messagelist.nextElement();
		pout.print(message + "\r\n");
		pout.flush();
		pout.close();
	  }
	}
	catch (IOException e)
	{
          System.out.println(e.toString());
	}
    }

  //向客户发送所有在聊天室中的用户
  protected void returnUserList(HttpServletResponse res)
  {
  	try
	{
		res.setDateHeader("Expires",System.currentTimeMillis());
		PrintStream pout = new PrintStream(res.getOutputStream());
		pout.print("+OK\r\n");
		Enumeration userlist= users.list();
		while (userlist.hasMoreElements())
		{
			pout.print((String)userlist.nextElement());
			pout.print("\r\n");
		}
		pout.print(".\r\n");
		pout.flush();
	}
	catch (IOException e)
	{
          System.out.println(e.toString());
	}
  }
}

class UsersList
{
  private Hashtable list = new Hashtable();
  private Hashtable active = new Hashtable();

  UsersList()
  {
  }

  protected synchronized boolean add(String user)
  {
    if (exists(user))
    {
	return false;
    }
    list.put(user,new MessageQueue());
    touch(user);
    return true;
  }

  protected synchronized Enumeration list()
  {
	return list.keys();
  }

  protected synchronized boolean drop(String user)
  {
	if (!exists(user))
	{
	  return false;
	}
	list.remove(user);
	active.remove(user);
	return true;
    }

  protected boolean exists(String user)
  {
	return list.containsKey(user);
  }

  protected void addMessage(MessageText message)
  {
	Enumeration allUsers = list.keys();
	while (allUsers.hasMoreElements())
	{
	  addUserMessage((String)allUsers.nextElement(),message);
	}
  }

  private void addUserMessage(String user,MessageText message)
  {
	((MessageQueue)list.get(user)).add(message);
  }

  //清除参数指定用户的消息队列
  protected void resetUser(String user)
  {
	((MessageQueue)list.get(user)).reset();
  }

  //返回参数中指定的消息队列中的信息，
  //并把它的活动时间改为当前的时间
  protected Enumeration getMessages(String user)
  {
	touch(user);
	return ((MessageQueue)list.get(user)).listMessages();
  }

  //设置用户的最近活动时间为当前的时间
  protected synchronized void touch(String user)
  {
	if (exists(user))
	{
  	  active.put(user,new Long(System.currentTimeMillis()));
	}
  }

  // 返回超时的用户
  protected synchronized Enumeration inactive(int timeout)
  {
	Vector inactive = new Vector();
	long now = System.currentTimeMillis();
	long when = now - timeout;
	Enumeration users = list.keys();
	while (users.hasMoreElements())
	{
	  String user = (String)users.nextElement();
	  if (((Long)active.get(user)).longValue()<when)
	  {
		inactive.addElement(user);
	  }
	}
	return inactive.elements();
      }
    }

class MessageQueue
{
  private Vector messageq = new Vector();

  MessageQueue()
  {
  }

  protected synchronized void add(MessageText message)
  {
	messageq.addElement(message);
	notifyAll();
  }

  protected synchronized Enumeration listMessages()
  {
	try
	{
	  if (messageq.isEmpty())
	  {
		wait(30*1000);
	  }
	}
	catch (InterruptedException ie)
	{
          System.out.println(ie.toString());
	}
	return messageq.elements();
  }

  protected synchronized void reset()
  {
	messageq.removeAllElements();
  }
}

class MessageText
{
  private String user;
  private String message;

  MessageText(String user,String message)
  {
	this.user = user;
	this.message = message;
  }

  public String toString()
  {
	return user + ":" + message;
  }

  protected String getUser()
  {
	return user;
  }

  protected String getMessage()
  {
	return message;
  }
}