监听器实现在线用户监控

川长思鸟来 2021-07-24 21:01 454阅读 0赞

**一 监听器**

RequestListener.java

package lee;
    
    import javax.servlet.*;
    import javax.servlet.http.*;
    import javax.servlet.annotation.*;
    
    import java.sql.*;
    
    
    @WebListener
    public class RequestListener
        implements ServletRequestListener
    {
        // 当用户请求到达、被初始化时触发该方法
        public void requestInitialized(ServletRequestEvent sre)
        {
            HttpServletRequest request = (HttpServletRequest)
                sre.getServletRequest();
            HttpSession session = request.getSession();
            // 获取session ID
            String sessionId = session.getId();
            // 获取访问的IP和正在访问的页面
            String ip = request.getRemoteAddr();
            String page = request.getRequestURI();
            String user = (String)session.getAttribute("user");
            // 未登录用户当游客处理
            user = (user == null) ? "游客" : user;
            try
            {
                DbDao dd = new DbDao("com.mysql.jdbc.Driver"
                    , "jdbc:mysql://localhost:3306/online_inf"
                    , "root" , "32147");
                ResultSet rs = dd.query("select * from online_inf where session_id=?"
                    , true , sessionId);
                // 如果该用户对应的session ID存在，表明是旧的会话
                if (rs.next())
                {
                    // 更新记录
                    rs.updateString(4, page);
                    rs.updateLong(5, System.currentTimeMillis());
                    rs.updateRow();
                    rs.close();
                }
                else
                {
                    // 插入该用户的在线信息
                    dd.insert("insert into online_inf values(? , ? , ? , ? , ?)",
                        sessionId , user , ip , page , System.currentTimeMillis());
                }
            }
            catch (Exception ex)
            {
                ex.printStackTrace();
            }
        }
        // 当用户请求结束、被销毁时触发该方法
        public void requestDestroyed(ServletRequestEvent sre)
        {
        }
    }

OnlineListener.java

package lee;
    
    import javax.servlet.*;
    import javax.servlet.annotation.*;
    import javax.servlet.http.*;
    
    import java.sql.*;
    import java.awt.event.*;
    
    
    @WebListener
    public class OnlineListener
        implements ServletContextListener
    {
        // 超过该时间（10分钟）没有访问本站即认为用户已经离线
        public final int MAX_MILLIS = 10 * 60 * 1000;
        // 应用启动时触发该方法
        public void contextInitialized(ServletContextEvent sce)
        {
            // 每5秒检查一次
            new javax.swing.Timer(1000 * 5 , new ActionListener()
            {
                public void actionPerformed(ActionEvent e)
                {
                    try
                    {
                        DbDao dd = new DbDao("com.mysql.jdbc.Driver"
                            , "jdbc:mysql://localhost:3306/online_inf"
                            , "root" , "32147");
                        ResultSet rs = dd.query("select * from online_inf" , false);
                        StringBuffer beRemove = new StringBuffer("(");
                        while(rs.next())
                        {
                            // 如果距离上次访问时间超过了指定时间
                            if ((System.currentTimeMillis() - rs.getLong(5))
                                > MAX_MILLIS)
                            {
                                // 将需要被删除的session ID添加进来
                                beRemove.append("'");
                                beRemove.append(rs.getString(1));
                                beRemove.append("' , ");
                            }
                        }
                        // 有需要删除的记录
                        if (beRemove.length() > 3)
                        {
                            beRemove.setLength(beRemove.length() - 3);
                            beRemove.append(")");
                            // 删除所有“超过指定时间未重新请求的记录”
                            dd.modify("delete from online_inf where session_id in "
                                + beRemove.toString());
                        }
                        dd.closeConn();
                    }
                    catch (Exception ex)
                    {
                        ex.printStackTrace();
                    }
                }
            }).start();
        }
        public void contextDestroyed(ServletContextEvent sce)
        {
        }
    }

**二 DAO**

package lee;
    
    import java.sql.*;
    
    
    public class DbDao
    {
        private Connection conn;
        private String driver;
        private String url;
        private String username;
        private String pass;
        public DbDao()
        {
        }
        public DbDao(String driver , String url
            , String username , String pass)
        {
            this.driver = driver;
            this.url = url;
            this.username = username;
            this.pass = pass;
        }
        // 下面是各个成员变量的setter和getter方法
        public void setDriver(String driver) {
            this.driver = driver;
        }
        public void setUrl(String url) {
            this.url = url;
        }
        public void setUsername(String username) {
            this.username = username;
        }
        public void setPass(String pass) {
            this.pass = pass;
        }
        public String getDriver() {
            return (this.driver);
        }
        public String getUrl() {
            return (this.url);
        }
        public String getUsername() {
            return (this.username);
        }
        public String getPass() {
            return (this.pass);
        }
        // 获取数据库连接
        public Connection getConnection() throws Exception
        {
            if (conn == null)
            {
                Class.forName(this.driver);
                conn = DriverManager.getConnection(url,username,
                    this. pass);
            }
            return conn;
        }
        // 插入记录
        public boolean insert(String sql , Object... args)
            throws Exception
        {
            PreparedStatement pstmt = getConnection().prepareStatement(sql);
            for (int i = 0; i < args.length ; i++ )
            {
                pstmt.setObject( i + 1 , args[i]);
            }
            if (pstmt.executeUpdate() != 1)
            {
                return false;
            }
            pstmt.close();
            return true;
        }
        // 执行查询
        public ResultSet query(String sql , boolean updatable , Object... args )
            throws Exception
        {
            PreparedStatement pstmt = null;
            if (updatable)
            {
                // 创建可更新的PreparedStatement
                pstmt = getConnection().prepareStatement(sql
                    , ResultSet.TYPE_SCROLL_INSENSITIVE
                    , ResultSet.CONCUR_UPDATABLE);
            }
            else
            {
                pstmt = getConnection().prepareStatement(sql);
            }
            for (int i = 0; i < args.length ; i++ )
            {
                pstmt.setObject( i + 1 , args[i]);
            }
            return pstmt.executeQuery();
        }
        // 执行修改
        public void modify(String sql , Object... args)
            throws Exception
        {
            PreparedStatement pstmt = getConnection().prepareStatement(sql);
            for (int i = 0; i < args.length ; i++ )
            {
                pstmt.setObject(i + 1 , args[i]);
            }
            pstmt.executeUpdate();
            pstmt.close();
        }
        // 关闭数据库连接的方法
        public void closeConn()
            throws Exception
        {
            if (conn != null && !conn.isClosed())
            {
                conn.close();
            }
        }
    }

**三 测试页面online.jsp**

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
    <%@ page import="java.sql.*,lee.*" %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title> 用户在线信息 </title>
        <meta name="website" content="http://www.crazyit.org" />
    </head>
    <body>
    在线用户：
    <table width="640" border="1">
    <%
    DbDao dd = new DbDao("com.mysql.jdbc.Driver"
        , "jdbc:mysql://localhost:3306/online_inf"
        , "root"
        , "32147");
    // 查询online_inf表（在线用户表）的全部记录
    ResultSet rs = dd.query("select * from online_inf" , false);
    while (rs.next())
    {%>
    <tr>
        <td><%=rs.getString(1)%>
        <td><%=rs.getString(2)%>
        <td><%=rs.getString(3)%>
        <td><%=rs.getString(4)%>
    </tr>
    <%}%>
    </body>
    </html>

**四 数据库**

drop database online_inf;
    
    create database online_inf;
    
    use online_inf;
    
    create table online_inf
    (
    session_id varchar(255) primary key,
    username varchar(255),
    user_ip varchar(255),
    access_res varchar(255),
    last_access bigint
    );

**五 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

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