JAVA-EE使用监听器BindingListener在JSP页面实时显示在线人数------计算机网络经典

冷不防 2024-02-21 12:23 17阅读 0赞

>     package com.bjpowernode.oa.web.action;
>     
>     import com.bjpowernode.oa.Pojo.User;
>     import com.bjpowernode.oa.utils.DBUtil;
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.*;
>     
>     import java.io.IOException;
>     import java.sql.Connection;
>     import java.sql.PreparedStatement;
>     import java.sql.ResultSet;
>     import java.sql.SQLException;
>     
>     @WebServlet({"/user/login","/user/exit"})
>     public class UserServlet extends HttpServlet
>     {
>         //JSessionID=??这个键值对数据就是cookie保存的信息
>         //对于session关联的cookie来说,这个cookie是保存在浏览器的运行内存中的
>         //用户再次发送请求的时候,会自动把运行内存中的cookie放到请求头内一并发送
>         //服务器就是根据这个值找到对应的对象
>         //session存储在服务器上的,cookie是储存在电脑机器上的
>         //cookie可以存在浏览器运行内存中,也可以放在硬盘内保存
>         //cookie和session都是为了保存会话的状态
>         //这两个机制存在的目的就是为了解决我们的http协议的无状态无连接协议的问题
>         //(无状态无连接)没有请求和响应时,双方不知道对方是否还在
>         @Override
>         public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
>             String servletPath = request.getServletPath();
>             request.setCharacterEncoding("UTF-8");
>             response.setContentType("text/html;charset=UTF-8");
>             if("/user/login".equals(servletPath))
>             {
>                 doLogin(request,response);
>             }
>             else if("/user/exit".equals(servletPath))
>             {
>                 doExit(request,response);
>             }
>         }
>         //将购物车中的商品编号放到cookie当中,cookie保存到硬盘
>         //下一次再打开,自动读取本地cookie,就还会显示这些商品
>         //购物网站未登录不允许查看商品和保存购物车的原理是,为了记录数据,什么用户喜欢什么样的东西
>         //和针对不同用户给出不同的优惠力度(大数据杀熟),并且可以防止爬虫,和减轻服务器压力(没有购买欲望的客户不让你看)
>         //十天免登录的实现原理如下,保存一个记录了用户名和密码的cookie到本地
>         //当十天内再次访问该网站时,会自动在请求头内发送这个账号用户名和密码到服务器,服务器接收到这个cookie
>         //解密后实现登录
>         //cookie和session都是Http协议的一部分,因为Http协议是无状态和无连接的协议
>         //Http协议规定,任何一个cookie都是由name和value组成的
>         //在java的servlet中,对cookie提供了那些支持?
>         //jakarta.servlet.http.HttpCookie
>         //Cookie是带有路径的,不同的cookie会带不同的路径,方便对应的提交信息和用于握手机制的实现
>         //我们java的cookie主要是在response中将信息作为回传给浏览器的,在服务器中只是做一个信息的处理
>         //在Http协议中规定如下,在浏览器发送请求时,会自动携带该路径下的cookie在请求头中给服务器
>         //cookie的name和value都是字符串,cookie的name和value都是字符串
>         private void doExit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             HttpSession session = request.getSession(false);
>             if(session != null && session.getAttribute("user") != null)
>             {
>                 //从session域中移除对象
>                 session.removeAttribute("user");
>                 //销毁session的方法,session.invalidate()
>                 session.invalidate();
>                 Cookie[] cookies = request.getCookies();
>                 for (Cookie cookie : cookies)
>                 {
>                     cookie.setMaxAge(0);
>                     cookie.setPath(request.getContextPath());
>                     response.addCookie(cookie);
>                 }
>                 response.sendRedirect(request.getContextPath());
>             }
>         }
>         protected void doLogin(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             String username = request.getParameter("username");
>             String password = request.getParameter("password");
>             String loginSet = request.getParameter("flag");
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             boolean flag = false;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 String sql = "select * from t_user where username = ? and pssword = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,username);
>                 statement.setString(2,password);
>                 resultSet = statement.executeQuery();
>                 if(resultSet.next())
>                 {
>                     flag = true;
>                 }
>     
>             }
>             catch (SQLException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(flag)
>             {
>                 HttpSession session = request.getSession();
>                 session.setAttribute("user",new User(username,password));
>                 if(loginSet != null && "1".equals(loginSet))
>                 {
>                     //存储登录名
>                     Cookie name = new Cookie("username",username);
>                     //存储密码
>                     Cookie LoginPassword = new Cookie("password",password);
>                     //生命周期都设为1小时,实验够了
>                     name.setMaxAge(60 * 60);
>                     LoginPassword.setMaxAge(60 * 60);
>                     //保存到浏览器中
>                     name.setPath(request.getContextPath());
>                     LoginPassword.setPath(request.getContextPath());
>                     //添加到响应中去
>                     response.addCookie(name);
>                     response.addCookie(LoginPassword);
>                 }
>                 response.sendRedirect(request.getContextPath() + "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     }
> 
>     package com.bjpowernode.oa.web.action;
>     
>     import com.bjpowernode.oa.Pojo.User;
>     import com.bjpowernode.oa.utils.DBUtil;
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.*;
>     
>     import java.io.IOException;
>     import java.sql.Connection;
>     import java.sql.PreparedStatement;
>     import java.sql.ResultSet;
>     import java.sql.SQLException;
>     
>     @WebServlet({"/user/login","/user/exit"})
>     public class UserServlet extends HttpServlet
>     {
>         //JSessionID=??这个键值对数据就是cookie保存的信息
>         //对于session关联的cookie来说,这个cookie是保存在浏览器的运行内存中的
>         //用户再次发送请求的时候,会自动把运行内存中的cookie放到请求头内一并发送
>         //服务器就是根据这个值找到对应的对象
>         //session存储在服务器上的,cookie是储存在电脑机器上的
>         //cookie可以存在浏览器运行内存中,也可以放在硬盘内保存
>         //cookie和session都是为了保存会话的状态
>         //这两个机制存在的目的就是为了解决我们的http协议的无状态无连接协议的问题
>         //(无状态无连接)没有请求和响应时,双方不知道对方是否还在
>         @Override
>         public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
>             String servletPath = request.getServletPath();
>             request.setCharacterEncoding("UTF-8");
>             response.setContentType("text/html;charset=UTF-8");
>             if("/user/login".equals(servletPath))
>             {
>                 doLogin(request,response);
>             }
>             else if("/user/exit".equals(servletPath))
>             {
>                 doExit(request,response);
>             }
>         }
>         //将购物车中的商品编号放到cookie当中,cookie保存到硬盘
>         //下一次再打开,自动读取本地cookie,就还会显示这些商品
>         //购物网站未登录不允许查看商品和保存购物车的原理是,为了记录数据,什么用户喜欢什么样的东西
>         //和针对不同用户给出不同的优惠力度(大数据杀熟),并且可以防止爬虫,和减轻服务器压力(没有购买欲望的客户不让你看)
>         //十天免登录的实现原理如下,保存一个记录了用户名和密码的cookie到本地
>         //当十天内再次访问该网站时,会自动在请求头内发送这个账号用户名和密码到服务器,服务器接收到这个cookie
>         //解密后实现登录
>         //cookie和session都是Http协议的一部分,因为Http协议是无状态和无连接的协议
>         //Http协议规定,任何一个cookie都是由name和value组成的
>         //在java的servlet中,对cookie提供了那些支持?
>         //jakarta.servlet.http.HttpCookie
>         //Cookie是带有路径的,不同的cookie会带不同的路径,方便对应的提交信息和用于握手机制的实现
>         //我们java的cookie主要是在response中将信息作为回传给浏览器的,在服务器中只是做一个信息的处理
>         //在Http协议中规定如下,在浏览器发送请求时,会自动携带该路径下的cookie在请求头中给服务器
>         //cookie的name和value都是字符串,cookie的name和value都是字符串
>         private void doExit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             HttpSession session = request.getSession(false);
>             if(session != null && session.getAttribute("user") != null)
>             {
>                 //从session域中移除对象
>                 session.removeAttribute("user");
>                 //销毁session的方法,session.invalidate()
>                 session.invalidate();
>                 Cookie[] cookies = request.getCookies();
>                 for (Cookie cookie : cookies)
>                 {
>                     cookie.setMaxAge(0);
>                     cookie.setPath(request.getContextPath());
>                     response.addCookie(cookie);
>                 }
>                 response.sendRedirect(request.getContextPath());
>             }
>         }
>         protected void doLogin(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             String username = request.getParameter("username");
>             String password = request.getParameter("password");
>             String loginSet = request.getParameter("flag");
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             boolean flag = false;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 String sql = "select * from t_user where username = ? and pssword = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,username);
>                 statement.setString(2,password);
>                 resultSet = statement.executeQuery();
>                 if(resultSet.next())
>                 {
>                     flag = true;
>                 }
>     
>             }
>             catch (SQLException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(flag)
>             {
>                 HttpSession session = request.getSession();
>                 session.setAttribute("user",new User(username,password));
>                 if(loginSet != null && "1".equals(loginSet))
>                 {
>                     //存储登录名
>                     Cookie name = new Cookie("username",username);
>                     //存储密码
>                     Cookie LoginPassword = new Cookie("password",password);
>                     //生命周期都设为1小时,实验够了
>                     name.setMaxAge(60 * 60);
>                     LoginPassword.setMaxAge(60 * 60);
>                     //保存到浏览器中
>                     name.setPath(request.getContextPath());
>                     LoginPassword.setPath(request.getContextPath());
>                     //添加到响应中去
>                     response.addCookie(name);
>                     response.addCookie(LoginPassword);
>                 }
>                 response.sendRedirect(request.getContextPath() + "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     }

>     <%@ page contentType="text/html;charset=UTF-8" language="java" %>
>     <%--引入标签库--%>
>     <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
>     <!DOCTYPE html>
>     <html>
>     <head>
>         <meta charset="utf-8">
>         <title>部门列表</title>
>         <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">
>     </head>
>     <body>
>     <script>
>         function del(dno){
>             var ok = window.confirm('亲,确认删除该数据吗?');
>             if(ok){
>                 document.location.href = "${pageContext.request.contextPath}/dept/delete?deptno=" + dno;
>             }
>         }
>     </script>
>         <h3>欢迎:<a href="">${user.username}</a>目前在线人数:${onlineCount}</h3>
>         <h3><a href="user/exit">退出登录</a></h3>
>     <h1 align="center">部门列表</h1>
>     <hr>
>         <table align="center" border="1px" width="50%">
>             <tr>
>                 <th>序号</th>
>                 <th>部门编号</th>
>                 <th>部门名称</th>
>                 <th>操作</th>
>             </tr>
>             <c:forEach items="${depts}" var="dept" varStatus="deptStatue">
>                 <tr>
>                     <td>${deptStatue.count}</td>
>                     <td>${dept.deptno}</td>
>                     <td>${dept.dname}</td>
>                     <td>
>                         <a href="javascript:void(0)" onclick="del(${dept.deptno})">删除</a>
>                         <a href="dept/detail?f=m&deptno=${dept.deptno}">修改</a>
>                         <a href="dept/detail?f=d&deptno=${dept.deptno}">详情</a>
>                     </td>
>                 </tr>
>             </c:forEach>
>         </table>
>         <hr>
>         <a href="add.jsp">新增部门</a>
>     </body>
>     </html>
> 
>     <%@ page contentType="text/html;charset=UTF-8" language="java" %>
>     <%--引入标签库--%>
>     <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
>     <!DOCTYPE html>
>     <html>
>     <head>
>         <meta charset="utf-8">
>         <title>部门列表</title>
>         <base href="${pageContext.request.scheme}://${pageContext.request.serverName}:${pageContext.request.serverPort}${pageContext.request.contextPath}/">
>     </head>
>     <body>
>     <script>
>         function del(dno){
>             var ok = window.confirm('亲,确认删除该数据吗?');
>             if(ok){
>                 document.location.href = "${pageContext.request.contextPath}/dept/delete?deptno=" + dno;
>             }
>         }
>     </script>
>         <h3>欢迎:<a href="">${user.username}</a>目前在线人数:${onlineCount}</h3>
>         <h3><a href="user/exit">退出登录</a></h3>
>     <h1 align="center">部门列表</h1>
>     <hr>
>         <table align="center" border="1px" width="50%">
>             <tr>
>                 <th>序号</th>
>                 <th>部门编号</th>
>                 <th>部门名称</th>
>                 <th>操作</th>
>             </tr>
>             <c:forEach items="${depts}" var="dept" varStatus="deptStatue">
>                 <tr>
>                     <td>${deptStatue.count}</td>
>                     <td>${dept.deptno}</td>
>                     <td>${dept.dname}</td>
>                     <td>
>                         <a href="javascript:void(0)" οnclick="del(${dept.deptno})">删除</a>
>                         <a href="dept/detail?f=m&deptno=${dept.deptno}">修改</a>
>                         <a href="dept/detail?f=d&deptno=${dept.deptno}">详情</a>
>                     </td>
>                 </tr>
>             </c:forEach>
>         </table>
>         <hr>
>         <a href="add.jsp">新增部门</a>
>     </body>
>     </html>

>     package com.bjpowernode.oa.Pojo;
>     
>     import jakarta.servlet.ServletContext;
>     import jakarta.servlet.http.HttpSessionBindingEvent;
>     import jakarta.servlet.http.HttpSessionBindingListener;
>     
>     public class User implements HttpSessionBindingListener
>     {
>         private String username;
>         private String password;
>     
>         public User() {
>         }
>     
>         @Override
>         public String toString() {
>             return "User{" +
>                     "username='" + username + '\'' +
>                     ", password='" + password + '\'' +
>                     '}';
>         }
>     
>         @Override
>         public void valueBound(HttpSessionBindingEvent event) {
>             ServletContext application = event.getSession().getServletContext();
>             Long onlineCount = (Long)application.getAttribute("onlineCount");
>             if(onlineCount == null)
>             {
>                 application.setAttribute("onlineCount",1L);
>             }
>             else
>             {
>                 onlineCount++;
>                 application.setAttribute("onlineCount",onlineCount);
>             }
>         }
>     
>         @Override
>         public void valueUnbound(HttpSessionBindingEvent event) {
>             //因为是推出登录,所以必定不会是null空值
>             ServletContext application = event.getSession().getServletContext();
>             Long onlineCount = (Long)application.getAttribute("onlineCount");
>             onlineCount--;
>             application.setAttribute("onlineCount",onlineCount);
>         }
>     
>         public String getUsername() {
>             return username;
>         }
>     
>         public void setUsername(String username) {
>             this.username = username;
>         }
>     
>         public String getPassword() {
>             return password;
>         }
>     
>         public void setPassword(String password) {
>             this.password = password;
>         }
>     
>         public User(String username, String password) {
>             this.username = username;
>             this.password = password;
>         }
>     }
> 
>     package com.bjpowernode.oa.Pojo;
>     
>     import jakarta.servlet.ServletContext;
>     import jakarta.servlet.http.HttpSessionBindingEvent;
>     import jakarta.servlet.http.HttpSessionBindingListener;
>     
>     public class User implements HttpSessionBindingListener
>     {
>         private String username;
>         private String password;
>     
>         public User() {
>         }
>     
>         @Override
>         public String toString() {
>             return "User{" +
>                     "username='" + username + '\'' +
>                     ", password='" + password + '\'' +
>                     '}';
>         }
>     
>         @Override
>         public void valueBound(HttpSessionBindingEvent event) {
>             ServletContext application = event.getSession().getServletContext();
>             Long onlineCount = (Long)application.getAttribute("onlineCount");
>             if(onlineCount == null)
>             {
>                 application.setAttribute("onlineCount",1L);
>             }
>             else
>             {
>                 onlineCount++;
>                 application.setAttribute("onlineCount",onlineCount);
>             }
>         }
>     
>         @Override
>         public void valueUnbound(HttpSessionBindingEvent event) {
>             //因为是推出登录,所以必定不会是null空值
>             ServletContext application = event.getSession().getServletContext();
>             Long onlineCount = (Long)application.getAttribute("onlineCount");
>             onlineCount--;
>             application.setAttribute("onlineCount",onlineCount);
>         }
>     
>         public String getUsername() {
>             return username;
>         }
>     
>         public void setUsername(String username) {
>             this.username = username;
>         }
>     
>         public String getPassword() {
>             return password;
>         }
>     
>         public void setPassword(String password) {
>             this.password = password;
>         }
>     
>         public User(String username, String password) {
>             this.username = username;
>             this.password = password;
>         }
>     }