一、简单理解MVC框架

经典MVC模式中，M是指业务模型，V是指用户界面，C则是控制器，使用MVC的目的是将M和V的实现代码分离，从而使同一个程序可以使用不同的表现形式。

其中，View的定义比较清晰，就是用户界面。Model即对数据进行逻辑处理的部分。Controller按照用户请求来选择对应的Model进行处理同时把处理结果返回到指定的jsp视图中，只是接收请求并决定调用哪个模型构件去处理请求，然后再确定用哪个视图来显示返回的数据。

二、项目结构

三、项目源码

3.1 User

代码如下（示例）：

public class User {
    // 封装实体类的JavaBean

    private String name;
    private String password;

    public User() {

    }

    // 构造方法用来传入数值
    public User(String name, String password) {
        this.name = name;
        this.password = password;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

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

}

3.2 UserDao

代码如下（示例）：

import java.sql.*;


//处理业务逻辑的JavaBean
public class UserDao {

    public static int login(User user) {
        int flag = -1;
        String NAME = "sa";
        String PASSWORD = "123456";
        String URL = "jdbc:sqlserver://localhost:1433;databaseName=test";

        Connection connection = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            // 1、加载驱动
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            // 2、建立连接
            connection = DriverManager.getConnection(URL, NAME, PASSWORD);

            // 3、操作数据库
            String sql = "select count(*) from admins where name=? and password=?";
            pstmt = connection.prepareStatement(sql);
            pstmt.setString(1, user.getName());
            pstmt.setString(2, user.getPassword());
            // 4、执行
            rs = pstmt.executeQuery();

            if (rs.next()) {
                flag = rs.getInt(1);
            }
            if (flag > 0) {// 登录成功
                return 1;
            } else {
                return 0;
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return -1;
        } catch (SQLException e) {
            e.printStackTrace();
            return -1;
        } catch (Exception e) {
            e.printStackTrace();
            return -1;
        } finally {

            try {
                if (rs != null) rs.close();
                if (pstmt != null) pstmt.close();
                if (connection != null) connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    }

}

3.3 RegisterDao

代码如下（示例）：

import java.sql.*;

//封装注册功能业务逻辑的JavaBean
public class RegisterDao {

    public static int register(User user) {
        int count = -1;
        String NAME = "sa";
        String PASSWORD = "123456";
        String URL = "jdbc:sqlserver://localhost:1433;databaseName=test";

        Connection connection = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            //1、加载驱动
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            //2、连接
            connection = DriverManager.getConnection(URL, NAME, PASSWORD);
            //操作数据库
            String sql = "insert into admins values(?,?)";//插入数据
            pstmt = connection.prepareStatement(sql);
            pstmt.setString(1, user.getName());
            pstmt.setString(2, user.getPassword());

            count = pstmt.executeUpdate();
            return count;

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return -1;
        } catch (SQLException e) {
            e.printStackTrace();
            return -1;
        } catch (Exception e) {
            e.printStackTrace();
            return -1;
        } finally {

            try {
                if (pstmt != null) pstmt.close();
                if (connection != null) connection.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }


    }


}

3.4 servletControll

代码如下（示例）：

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


/**
 * Servlet implementation class servletControll
 */
@WebServlet("/servletControll")
public class servletControll extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //取值
        request.setCharacterEncoding("utf-8");
        String name = request.getParameter("uname");
        String pwd = request.getParameter("upwd");
        //封装
        User user = new User(name, pwd);

        //调用业务逻辑层
        int result = UserDao.login(user);

        if (result > 0) {
            //登录成功
            response.sendRedirect("success.jsp");//重定向到成功界面
        } else {
            //登录失败
            response.sendRedirect("notsuccess.jsp");//定位到失败页面
        }
        //请求转发
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

3.5 servletControllRegister

代码如下（示例）：

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


/**
 * Servlet implementation class servletControllRegister
 */
@WebServlet("/servletControllRegister")
public class servletControllRegister extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //注册功能、、向数据库添加数据

        request.setCharacterEncoding("utf-8");
        String name = request.getParameter("uname");
        String pwd = request.getParameter("upwd");

        User user = new User(name, pwd);//保存客户端输入的信息

        int result = RegisterDao.register(user);
        if (result > 0) {
            //注册成功
            response.sendRedirect("login.jsp");
        } else {
            //注册失败重新注册
            response.sendRedirect("register.jsp");
        }
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

3.6 web.xml

代码如下（示例）：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <!-- 初始的页面 -->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
    <!-- 用户名和密码验证的servlet -->
    <servlet>
        <servlet-name>Login</servlet-name>
        <servlet-class>servletControll</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Login</servlet-name>
        <url-pattern>/user</url-pattern>
    </servlet-mapping>
    <!-- 显示欢迎的servlet -->
    <servlet>
        <servlet-name>Register</servlet-name>
        <servlet-class>servletControllRegister</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Register</servlet-name>
        <url-pattern>/register</url-pattern>
    </servlet-mapping>
</web-app>

3.7 login.jsp

代码如下（示例）：

<%--
  Created by IntelliJ IDEA.
  User: 10504
  Date: 2022/5/17
  Time: 12:49
  To change this template use File | Settings | File Templates.
--%>
登录页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
         pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>登录页面</title>
</head>
<body>

<form action="servletControll" method="post">

    用户名：<input type="text" name="uname"/>
    密码：<input type="password" name="upwd"/><br><br>
    <input type="submit" value="登录"/>
    <input type="reset" value="重置"/>
    <a href="register.jsp">注册新用户</a>
</form>

</body>
</html>

3.8 register.jsp

代码如下（示例）：

<%--
  Created by IntelliJ IDEA.
  User: 10504
  Date: 2022/5/17
  Time: 12:55
  To change this template use File | Settings | File Templates.
--%>
注册页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
         pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>

<form action="servletControllRegister" method="post">

    用户名：<input type="text" name="uname"/>
    密码：<input type="password" name="upwd"/>
    <input type="submit" value="注册"/>
</form>

</body>
</html>

3.9 success.jsp

代码如下（示例）：

<%--
  Created by IntelliJ IDEA.
  User: 10504
  Date: 2022/5/17
  Time: 13:29
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录成功</title>
</head>
<body>
欢迎您的使用！
</body>
</html>

3.10 failure.jsp

代码如下（示例）：

<%--
  Created by IntelliJ IDEA.
  User: 10504
  Date: 2022/5/17
  Time: 13:42
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录失败</title>
</head>
<body>

</body>
</html>