使用监听查看在线用户

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监听器

Servlet JSP SQL Server SQL HTML

（－）使用监听查看在线用户

1 显示层（一）登录界面index.jsp

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <title>index.html</title>

    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

    

</head>

<body>
    <CENTER>
     <H2>在线系统</H2>
     <FORM action="CheckInfo" method="post">
     请输入用户名
     <INPUT type="text" name="name"><BR>
     请输入密码
     <INPUT type="password" name="password"><BR>
     <INPUT type="submit" value="登录">
     </FORM>
    </CENTER>
</body>
</html>

2 显示层（二）index.jsp

<%@ page language="java" import="java.util.*,com.*" pageEncoding="UTF-8"%>
<%@ page import="com.UserListener" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">

    
</head>
<%
    UserList userList=UserList.getUserList();
    UserListener ul=new UserListener();

%>
<body>
    <CENTER>
     <H2>在线用户名单</H2>
     <P>
      <TEXTAREA rows="10" cols="20">
        <%
          Vector vector=userList.getList();
          if(vector!=null&&vector.size()>0)
          {
            for(int i=0;i<vector.size();i++)
            {
               out.println(vector.elementAt(i));
            }
          }
        %>
      </TEXTAREA>
     </P>
    </CENTER>
</body>
</html>

3 Servlet处理层CheckInfo.java

package com;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
public class CheckInfo extends HttpServlet {

private ServletRequest session;
/**
* Constructor of the object.
*/
public CheckInfo() {
super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

response.setContentType("text/html");
// PrintWriter out = response.getWriter();
// out
//    .println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
// out.println("<HTML>");
// out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
// out.println(" <BODY>");
// out.print("    This is ");
// out.print(this.getClass());
// out.println(", using the POST method");
// out.println(" </BODY>");
// out.println("</HTML>");
// out.flush();
// out.close();
UserList userList=UserList.getUserList();
UserListener ul=new UserListener();
String name=request.getParameter("name");
String password=request.getParameter("password");
//测试
// System.out.println(name);
// System.out.println(password);
if(check(name,password))
{
   //System.out.println("haha");
   ul.setUser(name);
   //System.out.println(name);
      //session.setAttribute("list",ul);
      request.getSession(true).setAttribute("list",ul);
      userList.addUser(ul.getUser());
      response.sendRedirect("index.jsp");
}
else
{
   response.sendRedirect("error.jsp");
}
}
   public boolean check(String name,String password)
   {
    boolean check=false;
    try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
    try {
Connection con=DriverManager.getConnection("jdbc:odbc:myDB");
//String sql="select * from student where username"+"=?"+" and "+"password"+"=?";
String sql="select * from student where username=? and password=?";
     PreparedStatement stat=con.prepareStatement(sql);
stat.setString(1,name);
stat.setString(2,password);
ResultSet rs=stat.executeQuery();
if(rs.next())
{
   System.out.println("OK");
   check=!check;
}
if(con!=null)
   try {
    con.close();
   } catch (SQLException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

    return check;
   }
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occure
*/
public void init() throws ServletException {
// Put your code here
}

}

4 模型层（－）UserList.java

package com;

import java.util.Vector;

public class UserList
{
   Vector container;
   private static UserList userList=new UserList();
   private UserList()
   {
    container=new Vector();
   }
   public static UserList getUserList()
   {
    return userList;
   }
   public void addUser(String user)
   {
    if(user!=null)
    {
     container.addElement(user);
    }
   }
   public Vector getList()
   {
    return container;
   }
   public void removeUser(String user)
   {
    if(user!=null)
    {
     container.removeElement(user);
    }
   }
}
5 模型层（二）UserListener.java

package com;

import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

public class UserListener implements HttpSessionBindingListener
{
    private String user;
    private UserList userList=UserList.getUserList();
    public UserListener()
    {
     user="";
    }
    public void setUser(String user)
    {
     this.user=user;
    }
    public String getUser()
    {
     return user;
    }
public void valueBound(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
System.out.println(user+"用户上线");
}
public void valueUnbound(HttpSessionBindingEvent arg0) {
// TODO Auto-generated method stub
userList.removeUser(user);
System.out.println(user+"用户下线");
}
}

6 显示层（三）error.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>My JSP 'error.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">

    
</head>

<body>
    错误<A href="index.html">fanhui</A>
</body>
</html>

几点说明

1 需要一个数据库，这里的表名为student

2 使用了HttpSessionBingdingListener接口。此接口是唯一一个不用web.xml中设置的接口

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用户登录和退出日志 | 使用监听器Servlet

2007-03-29 16:08
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