实现简单登陆 session绑定控制

小咪咪 2022-07-14 12:07 145阅读 0赞

## 实现登陆 ##

先创建一个存储用户的表

mysql> create table user(
        -> id int primary key auto_increment,     -> username varchar(50) unique,     -> pwd varchar(30),     -> name varchar(250),     -> gender char(1)     -> ); Query OK, 0 rows affected (0.17 sec)

注意：unique 唯一性约束，让用户名唯一。  
增加用户

insert into user(username,pwd,name,gender) values(‘Recar’,’123456’,’Recar’,’m’);

写一个登陆.jsp 和登陆成功.jsp

要做错误判断。最后做session验证。

![这里写图片描述][SouthEast]

在登陆成功后，在session上绑定个user。然后在success.jsp页面进行判断是否有这个绑定的，有就继续执行。没有则跳转到登陆界面。并且方法返回。不在继续执行。

**实现：**  
先输入logon.do或者logon.jsp  
然后进行登陆。**post**将数据提交给**控制器 ActionServlet**。进行判断。是否有这个用户。然后在判断密码是否正确。通过DAO来操作数据库。存在并且密码正确进入success.jsp页面。不成功则**重定向到登陆界面**。在success.jsp页面也进行判断。是否有session，并且这个**session绑定有user**。有就可以进入这个页面。没有则跳转到登陆界面。**返回方法**。

![这里写图片描述][SouthEast 1]

UserDao.java

package dao;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    
    import entity.User;
    import util.DBUtil;
    public class UserDao { 
        public User findByUsername(String username) throws Exception{
            User user =null;
            Connection conn =null;
            PreparedStatement prep = null;
            ResultSet rst = null;
            try{
                conn = DBUtil.getConnection();
                prep = conn.prepareStatement("select * from user where username=?");
                prep.setString(1, username);
    
                rst = prep.executeQuery();
                if(rst.next()){
                    user = new User();
                    user.setId(rst.getInt("id"));
                    user.setUsername(username);
                    user.setPwd(rst.getString("pwd"));
                    user.setName(rst.getString("name"));
                    user.setGender(rst.getString("gender"));
    
                }
    
            }catch(Exception e){
                e.printStackTrace();
                throw e;
            }finally{
                DBUtil.close(conn);
            }
    
    
            return user;
    
        }
    
        public static void main (String[] args) throws Exception{
            UserDao ud = new UserDao();
            User user =ud.findByUsername("ddd");
            System.out.println(user);
        }
    
    }

User.java

package entity;
    /** * 实体类 * @author Administrator * */
    public class User { 
        private int id;
        private String username;
        private String pwd;
        private String name;
    
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getUsername() {
            return username;
        }
        public void setUsername(String username) {
            this.username = username;
        }
        public String getPwd() {
            return pwd;
        }
        public void setPwd(String pwd) {
            this.pwd = pwd;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getGender() {
            return gender;
        }
        public void setGender(String gender) {
            this.gender = gender;
        }
        private String gender;
    
        @Override
        public String toString() {
    
            return id+""+username+""+pwd+""+name+""+gender;
        }
    
    
    }

DBUtil.java

package util;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.SQLException;
    
    
    /** * JDBC工具类： * 提供了获得连接，关闭连接的相关的方法。 * @author Administrator * */
    public class DBUtil { 
        //获得连接
        public static Connection getConnection(){
            Connection conn =null;
    
            try {
                Class.forName("com.mysql.jdbc.Driver");
    
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/jsd1507db", "root", "root");
    
    
    
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                try {
    
                    //将异常抛出！是分层的，本层不解决也不直接去显示，而是抛给他的下一层
                    throw e;
                } catch (Exception e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }
    
            return conn;
    
        }
        //关闭连接
        public static void close(Connection conn){
    
            if(conn!=null){
    
            }
                try {
    
                    conn.close();
                } catch (SQLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
    
                }
    
        }
        //写个主方法，可以检测是否成功拿到conn
        public static void main(String[] args){
            Connection conn = getConnection();
            System.out.println(conn);
    
        }
    
    
    
    
    }

ActionServlet.java

package web;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    import dao.UserDao;
    import entity.User;
    
    public class ActionServlet extends HttpServlet {
    
        public void service(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            request.setCharacterEncoding("utf-8");
            response.setContentType("text/html;charset=utf-8");
            PrintWriter out = response.getWriter();
        //分享请求资源路径
            String uri = request.getRequestURI();
            String action = uri.substring(uri.lastIndexOf("/"),uri.lastIndexOf("."));
            System.out.println("URI!!!"+action);
            if("/logon".equals(action)){
                //读取用户名和密码
                String username = request.getParameter("username");
                String password = request.getParameter("password");
                System.out.println(username);
                //根据用户名和密码查询数据库中是否有这个用户
                UserDao ud = new UserDao();
                try {
                    User user = ud.findByUsername(username);
                    if(user!=null&& password.equals(user.getPwd())){
                         //用户有，并且密码对了。登陆成功！
                        HttpSession session = request.getSession();
                        session.setAttribute("user", username);
                        response.sendRedirect("success.jsp");
    
                    }else{
                        out.print("用户名或者密码错误");
                        response.sendRedirect("logon.jsp");
    
                    }
    
    
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                    throw new ServletException(e);
                }
    
            }
    
    
            out.close();
        }
    
    }

logon.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 XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>用户登陆检测</title>
    
    <style type="text/css"> body { background-image: url(ruidian_sidegeermo_fengjing.jpg); background-attachment: fixed; background-repeat: no-repeat; background-size: 100% 100%; color: #FFF; font-family: "微软雅黑"; font-size: 1.6em; } #div1 { margin: 120px; margin-left: 530px; text-align: center; width: 200px; height: 200px; } #div2 { background-image: url(1.png); background-repeat: no-repeat; height: 100px; margin-top: 120px; margin-left: 580px; width: 200px; } span { font-size: 9px; } #b1 { } </style>
    </head>
    
    <body>
    <div id="div2"></div>
    <div id="div1">
      <form action="logon.do" method="post">
        <p>
          <label for="username">用户名</label>
          <input type="text" name="username" />
        </p>
        <p>
          <label for="password">密码</label>
          <input type="password" name="password"/>
        </p>
        <input type="submit" value="登陆" />
        <p> <span id="span"></span> </p>
      </form>
    </div>
    </body>
    </html>

success.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>
    
     <% Object obj = session.getAttribute("user"); if(obj==null){ response.sendRedirect("logon.do"); //但是后面的java代码还会执行。。。。于是 return ; } %> 
    
    
    <!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>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>Recar的网址导航~</title>
    <style type="text/css"> body{ background-image:url(ruidian_sidegeermo_fengjing.jpg);background-attachment:fixed;background-repeat:no-repeat; background-size:100%;font-family:'微软雅黑';color:#FFF; } a{ color:#FFF;text-decoration:none;margin:50px; } div{ width:100%;height:200px; border:1px solid #000;} table{ margin-left:150px;} div p{ font-size:20px;} #myblog a{ color:#FFF;text-decoration:none;text-align:center;} </style>
    
    
    </head>
    
    <body>
    
    <br/>
    <div > 
    
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    <div >
     <p >python</p >
     <table>
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    <div id="myblog"> <a href="http://blog.csdn.net/qq_28295425" target="_blank">我的CSDN</a></div>
    </body>
    </html>

## 效果： ##

登陆:  
![这里写图片描述][SouthEast 2]

![这里写图片描述][SouthEast 3]  
登陆成功！  
![这里写图片描述][SouthEast 4]

**没有进行登陆的话就不能获取绑定user的session。就不能进入success.jsp**

[SouthEast]: /images/20220714/7acbfa2e8685471995dcb1b10ea4856c.png
[SouthEast 1]: /images/20220714/a47d3587c4a245c287c51256959bc705.png
[SouthEast 2]: /images/20220714/ce4a8025f3d748b2ba85f5ecfb3c635f.png
[SouthEast 3]: /images/20220714/18fa32f18c7c49c1b13d112bad38a2fc.png
[SouthEast 4]: /images/20220714/925d897705154abba7a38525d5732a50.png