servlet+jdbc+jsp实现登录界面的验证（基于MVC思想）

发布时间：2024年01月06日

一、MVC的概念

MVC是模型(Model)和视图(View)以及控制器(Controller)的简写，是一种将数据、界面显示和业务逻辑进行分离的组织方式，这样在改进界面及用户交互时，不需要重新编写业务逻辑，从而提高了代码的可维护性。

M：主要用于封装业务数据的JavaBean(Bean) 和业务逻辑的JavaBean(Service)及访问数据库的

DAO对象。

V：主要负责数据收集和数据展现，通常由JSP文件完成。
C：主要负责流程控制和页面跳转，通常由Servlet完成。

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原始的登录验证方法：

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改进的登录验证方法：

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这样实现了解耦，从而具备了更好的扩展性。

二、需求

浏览器进入登录界面，输入用户名、密码，发送到服务器。
服务器完成数据库查询和验证，返回验证结果。
验证结果呈现在响应界面上。

三、代码演示

1、编写登录界面

创建空工程，在工程中创建javaEE模块
配置中设置tomcat的部署

编写login界面

<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
  <title>JSP - login</title>
</head>
<body>
<form action="loginServlet" method="post">
  用户名：<input type="text" name="userName"><br>
  密  码：<input type="text" name="password"><br>
  <input type="submit" value="登录">
</form>
</body>

```

2、编写LoginServlet实现获取用户名和密码

编写servlet

LoginServlet

package com.example.login_demo.servlet;

import com.example.login_demo.pojo.User;
import com.example.login_demo.service.UserService;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "LoginServlet", value = "/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、获取的用户名和密码
        String userName = request.getParameter("userName");
        System.out.println("获取的用户名：" + userName);
        String password = request.getParameter("password");
        System.out.println("获取的密码：" + password);
    }
}

单元测试：
- 运行tomcat
- 访问登录界面，发送登录请求

3、操作数据库部分

数据准备，db_web数据库下准备t_user表

编写DbUtils，实现jdbc的封装

package com.example.login_demo.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DbUtils {

    private static String jdbcName;
    private static String dbUrl;
    private static String dbUserName;
    private static String dbPassword;

    static {
        jdbcName = "com.mysql.jdbc.Driver";
        dbUrl = "jdbc:mysql://localhost:3306/db_web?useSSL=false";
        dbUserName = "root";
        dbPassword = "root";
        try {
            Class.forName(jdbcName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        Connection connection = DriverManager.getConnection(dbUrl, dbUserName, dbPassword);
        return connection;
    }

    public static void closeResource(Connection connection, PreparedStatement preparedStatement) throws SQLException {
        if (null != connection){
            connection.close();
        }
        if (null != preparedStatement){
            preparedStatement.close();
        }
    }

}

原始数据类型User

package com.example.login_demo.pojo;

public class User {

  private int id;

  private String userName;

  private String password;

  public User(String userName, String password) {
      this.userName = userName;
      this.password = password;
  }

  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 getPassword() {
      return password;
  }

  public void setPassword(String password) {
      this.password = password;
  }

  @Override
  public String toString() {
      return "User{" +
              "id=" + id +
              ", userName='" + userName + '\'' +
              ", password='" + password + '\'' +
              '}';
  }
}

dao层直接操作数据库

UserDao接口

package com.example.login_demo.dao;

import com.example.login_demo.pojo.User;

public interface UserDao {

    //查询用户
    User userLogin(User user);
}

UserDaoImpl接口实现类

package com.example.login_demo.dao;

import com.example.login_demo.pojo.User;
import com.example.login_demo.utils.DbUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserDaoImpl implements UserDao {
    @Override
    public User userLogin(User user) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            //1、获取数据库连接
            connection = DbUtils.getConnection();

            //2、准备sql语句
            String sql = "select * from t_user where userName = ? and password = ?";

            //3、执行sql返回结果
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setString(1, user.getUserName());
            preparedStatement.setString(2, user.getPassword());
            resultSet = preparedStatement.executeQuery();
            if (resultSet.next()){
                User returnUser = new User(resultSet.getString("userName"), resultSet.getString("password"));
                returnUser.setId(Integer.parseInt(resultSet.getString("id")));
                return returnUser; //查找成功
            }
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            //4、释放资源
            try {
                DbUtils.closeResource(connection, preparedStatement);
                if (null != resultSet){
                    resultSet.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return null;//查找失败
    }

    public static void main(String[] args) {
        UserDao userDao = new UserDaoImpl();
        User admin = userDao.userLogin(new User("admin", "12345"));
        System.out.println("查找到的用户：" + admin);
    }
}

单元测试：
- 执行UserDaoImpl中的测试代码

4、service层实现

UserDaoFactory实现：简单的静态工厂实现UserDao的实例创建，实现创建和使用的解耦

package com.example.login_demo.factory;

import com.example.login_demo.dao.UserDao;
import com.example.login_demo.dao.UserDaoImpl;

public class UserDaoFactory {

    public static UserDao getUserDao(){
        return new UserDaoImpl();
    }
}

service层实现dao层调用

package com.example.login_demo.service;

import com.example.login_demo.dao.UserDao;
import com.example.login_demo.factory.UserDaoFactory;
import com.example.login_demo.pojo.User;

public class UserService {
    private UserDao userDao;

    public UserService(){
        this.userDao = UserDaoFactory.getUserDao();
    }

    public User userLoginService(User user){
        return userDao.userLogin(user);
    }

}

5、修改Servlet，实现数据库的查找验证

LoginServlet

package com.example.login_demo.servlet;

import com.example.login_demo.pojo.User;
import com.example.login_demo.service.UserService;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "LoginServlet", value = "/loginServlet")
public class LoginServlet extends HttpServlet {
  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      this.doPost(request, response);
  }

  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      //1、获取的用户名和密码
      String userName = request.getParameter("userName");
      System.out.println("获取的用户名：" + userName);
      String password = request.getParameter("password");
      System.out.println("获取的密码：" + password);
      //2、创建UserService类型的对象实现数据的校验功能
      UserService userService = new UserService();
      User user = userService.userLoginService(new User(userName, password));
      if (null != user){
          System.out.println("登录成功！");
      }else {
          System.out.println("登录失败！");
      }
  }
}

单元测试：

6、修改Servlet，实现页面的跳转

修改LoginServlet，当成功时，跳转到成功界面；当失败时，跳转回登录界面并显示账号或者密码错误

package com.example.login_demo.servlet;

import com.example.login_demo.pojo.User;
import com.example.login_demo.service.UserService;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;

@WebServlet(name = "LoginServlet", value = "/loginServlet")
public class LoginServlet extends HttpServlet {
  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      this.doPost(request, response);
  }

  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      //1、获取的用户名和密码
      String userName = request.getParameter("userName");
      System.out.println("获取的用户名：" + userName);
      String password = request.getParameter("password");
      System.out.println("获取的密码：" + password);
      //2、创建UserService类型的对象实现数据的校验功能
      UserService userService = new UserService();
      User user = userService.userLoginService(new User(userName, password));
      if (null != user){
          System.out.println("登录成功！");
          //登录成功的信息放入session对象实现多个请求共享
          request.getSession().setAttribute("user", user);
          //实现客户端跳转
          response.sendRedirect("main.jsp");

      }else {
          System.out.println("登录失败，用户名或者密码错误！");
          request.setAttribute("error", "登录失败，用户名或者密码错误！");
          //实现服务器跳转，使用转发，共享request
          RequestDispatcher requestDispatcher = request.getRequestDispatcher("login.jsp");
          requestDispatcher.forward(request, response);
      }
  }
}

main.jsp

<%@ page import="com.example.login_demo.pojo.User" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>主页面</title>
</head>
<body>
<h1>登录成功！欢迎 <%=(User)session.getAttribute("user")%> !</h1>
</body>
</html>

<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
 <title>JSP - login</title>
</head>
<body>
<form action="loginServlet" method="post">
 用户名：<input type="text" name="userName"><br>
 密  码：<input type="text" name="password"><br>
 <span style="color: red"><%=request.getAttribute("error") == null?"":request.getAttribute("error")%></span><br>
 <input type="submit" value="登录">
</form>
</body>
</html>

测试：

文章来源:https://blog.csdn.net/CAUC_lin/article/details/135423929
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