session实现用户登陆功能

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>登陆页面</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>

    <form action="/Session/servlet/LoginServlet" method="post">
        用户名：<input type="text" name="username"><br/>
        密码：<input type="password" name="password"><br/>
        <input type="submit" value="登陆">
    </form>


  </body>
</html>

package login;

public class User
{
    private String username;
    private String password;

    public User() {
        super();
        // TODO Auto-generated constructor stub
    }
    public User(String username, String password) {
        super();
        this.username = username;
        this.password = password;
    }
    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;
    }


}

package 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.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User user = DB.find(username, password);  //html
        if(user==null){
            out.write("用户名或密码有误！！");
            return;
        }

        request.getSession().setAttribute("user", user);  //向用户session中存一个登陆标记，也就是让用户登陆成功

        response.sendRedirect("/Session/index1.jsp");


    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        doGet(request, response);
    }
}

class DB
{
    private static List<User> list = new ArrayList();
    static{
        list.add(new User("aaa","123"));
        list.add(new User("bbb","123"));
        list.add(new User("ccc","123"));
    }


    public static User find(String username ,String password){
        for(User user : list){
            if(user.getUsername().equals(username) && user.getPassword().equals(password)){
                return user;
            }
        }
        return null;
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@page import="login.User"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'index.jsp' starting page</title>
  </head>

  <body>

    欢迎您：
    <% 
        User user = (User)session.getAttribute("user");
        if(user!=null) out.write(user.getUsername());
    %>

    <br/><br/>
    <a href="/Session/login.html">登陆</a>

  </body>
</html>

浏览器输入:http://localhost:8080/Session/login.html
对用户名和密码进行输入：
输入错误用户名和密码：：
这里写图片描述
登陆：

输入正确的用户名和密码：
这里写图片描述
登陆：

session实现用户登陆功能

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