【JSP开发】有关session的登录注销的一个小例子

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下面是一个session的应用的小例子，是用来注销登录的
登陆界面的代码:
login.html:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>login.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">        <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->  </head>    <body>    <form action="/day07/LoginServlet" method="post">          用户名：<input text="text" name="username"><br/>          密码：  <input text="password" name="password"><br/>    <input type="submit" value="登陆">  </body></html>

用户的javaBean
User.java:

package cn.edu.login;public class User {    private String username;    private String password;   public User(String username, String password) {super();this.username = username;this.password = password;}public User(){super();}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;}        }

处理登录信息的Servlet，如果用户账号密码输入正确，就让用户跳转到欢迎界面，顺

便将用户信息加入到session中。
LoginServlet:

package cn.edu.login;import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("UTf-8");response.setContentType("text/html;charset=UTF-8");PrintWriter out=response.getWriter();       String username=request.getParameter("username");         String password=request.getParameter("password");              List<User> list=Db.getAll();//这里的Db是我自己写的假数据库，里面有一些User的账号密码信息，是内部类，在下面有       for(User user:list){       if(user.getUsername().equals(username)&&user.getPassword().equals(password)){       request.getSession().setAttribute("user", user);//登陆成功，向session中存入一个登陆标记       response.sendRedirect("/day07/index.jsp");          return;       }       }              out.write("用户名或者密码错误！");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request,response);}}//模拟数据库(上面提到的)class Db{private static List<User> list=new ArrayList<User>();static{list.add(new User("aaa","123"));list.add(new User("bbb","123"));list.add(new User("ccc","123"));}public static List getAll(){return list;}}

欢迎界面，可以从session中拿出用户姓名信息显示在主页上
index.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>    <title>My JSP 'index.jsp' starting page</title>    <mate http-equiv="content-type" content="text/html;charset=UTF-8">  </head>    <body>     欢迎您！${user.username}      <br/>  <a href="/day07/login.html">登录</a>  <a href="/day07/LogoutServlet">退出登录</a>  </body></html>

//注销时使用的Servlet，将session中加入的用户信息清除

LogoutServlet:

package cn.edu.login;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;//完成用户注销public class LogoutServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {HttpSession session=request.getSession(false);if(session==null){response.sendRedirect("/day07/index.jsp");return;}session.removeAttribute("user");response.sendRedirect("/day07/index.jsp");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {       doGet(request,response);}}

这样，当用户点击退出登录的时候，session中就没有用户的相应信息，用户再次进入主页或登录页面的时候，就会显示用户没有登录。

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