基于MVC+三层架构实现—SMS_登陆注册

╰+攻爆jí腚メ 2022-05-27 11:25 214阅读 0赞

> 做了一个简单的登录注册系统，基于MVC+三层架构的模式，关于MVC+三层架构模式的理解可以看这篇博客 [https://blog.csdn.net/w\_linux/article/details/79919523][https_blog.csdn.net_w_linux_article_details_79919523]

> 下面是开发全过程

### 项目目录 ###

![这里写图片描述][70]

### 一、创建数据库(MySQL) ###

create database sms;
    
    use sms;
    
    create table student(
      id int(5) primary key auto_increment,
      num varchar(5),
      password varchar(32),
      name varchar(32),
      age int(3),
      score double
      );
    #插入一条记录用来之后的测试
    insert into student(id,num,password,name,age,score)
                values(1,0001,123,'linjie',21,99);

![这里写图片描述][70 1]

--------------------

### 二、JavaBean创建 ###

> 因为在三层架构中View层、Service层、Dao层各司其职，而在MVC中三者model、view、controller三者合起来算是三层架构中的View层，JavaBean相当于model用来承载数据

package linjie.com.beans;
    
    import java.io.Serializable;
    
    public class Student implements Serializable {
        private Integer id;         //学生ID
        private String num;         //学号
        private String name;        //姓名
        private String password;    //密码
        private int age;            //年龄
        private double score;       //成绩
    
        //无参构造器
        public Student() {
            super();
        }
        //带参构造器
        public Student(String num, String name, int age, double score) {
            super();
            this.num = num;
            this.name = name;
            this.password = password;
            this.age = age;
            this.score = score;
        }
    
        //setters/getters
        public Integer getId() {
            return id;
        }
        public void setId(Integer id) {
            this.id = id;
        }
        public String getNum() {
            return num;
        }
        public void setNum(String num) {
            this.num = num;
        }
        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;
        }
        public int getAge() {
            return age;
        }
        public void setAge(int age) {
            this.age = age;
        }
        public double getScore() {
            return score;
        }
        public void setScore(double score) {
            this.score = score;
        }
    
    }

--------------------

### 三、建立login.jsp ###

> 从三层架构里的View层开始上面JavaBean已经完成，现在就是MVC中的view了，当然我这里是用已经完成得项目来写，所以里面有些并没有出现的东西，不需要惊讶。

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>SMS登录页面</title>
    </head>
    <body>
        ${message }<br>
        <form action="${pageContext.request.contextPath }/loginservlet" method="POST">
            学号：<input type="text" name="num"/><br>
            密码：<input type="password" name="password"/><br>
            <input type="submit" value="登录">
        </form>
        <a href="${pageContext.request.contextPath }/toRegisterServlet">注册</a>
    </body>
    </html>

### 四、建立LoginServlet.java（servlet） ###

> model和view写完了，就要写控制器了，servlet就是控制器

#### 控制器中的步骤如下 ####

*  接收请求参数
 *  创建Service对象
 *  调用Service对象的chaeckUser()方法对用户进行验证
 *  验证通过和未通过情况分析
    
        package linjie.com.servlets;
        
        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;
        
        import linjie.com.beans.Student;
        import linjie.com.service.IStudentService;
        import linjie.com.service.StudentServiceImpl;
        
        public class LoginServlet extends HttpServlet {
            protected void doPost(HttpServletRequest request, HttpServletResponse response) 
                    throws ServletException, IOException {
        
                //1、接收请求参数
                String num = request.getParameter("num");
                String password = request.getParameter("password");
        
                //获取Session
                HttpSession session = request.getSession();
        
                if(num==null || "".equals(num.trim())) {
                    session.setAttribute("message", "学号输入有误");
                    response.sendRedirect(request.getContextPath()+"/login.jsp");
                    return;
                }
                if(password==null || "".equals(password.trim())) {
                    session.setAttribute("message", "密码输入有误");
                    response.sendRedirect(request.getContextPath()+"/login.jsp");
                    return;
                }
        
                //2、创建Service对象
                IStudentService service = new StudentServiceImpl();
        
                //3、调用Service对象的chaeckUser()方法对用户进行验证
                Student student = service.checkUser(num,password);
        
                //4、验证未通过，则跳转到登录页面，让用户再次输入登录信息。此时页面需要给出用户一些提示
                if(student==null) {
                    session.setAttribute("message", "用户名或密码输入有误");
                    response.sendRedirect(request.getContextPath()+"/login.jsp");
                    return;
                }
        
                //4、验证通过，则跳转到系统主页index.jsp
                session.setAttribute("welcomeUser", num);
                response.sendRedirect(request.getContextPath()+"/index.jsp");
            }
        
        }

#### 注意一： ####

if(num == null || "".equals(num.trim()))

> num==null防止用户直接通过地址栏访问，而不是通过表单输入
> 
> “”.equals(num.trim())防止用户输入空串

#### 注意二： ####

##### 为什么要在servlet中创建Service对象？ #####

> 因为该项目是MVC+三层架构模型，所以servlet属于控制器，而系统业务逻辑需要在service中写(这里指验证用户请求参数)，所以需要创建Service对象

--------------------

### 五、消除servlet中的异常——>建立service接口以及其实现类 ###

> 因为在servlet中已经创建了service对象，然而并没有创建这个接口以及其实现类。所以需要通过ctrl+1来消除servlet异常，并创建相应的接口或实现类

#### IStudentService接口 ####

> 第二个saveStudent方法是之后用到的

package linjie.com.service;
    
    import linjie.com.beans.Student;
    
    public interface IStudentService {
    
        //对用户进行验证   
        Student checkUser(String num, String password);
        //向DB中添加Student
        Integer savaStudent(Student student);
    
    }

#### StudentServiceImpl实现类 ####

package linjie.com.service;
    
    import linjie.com.beans.Student;
    import linjie.com.dao.IStudentDao;
    import linjie.com.dao.StudentDaoImpl;
    
    public class StudentServiceImpl implements IStudentService {
        private IStudentDao dao;
    
        public StudentServiceImpl() {
            dao = new StudentDaoImpl();
        }
    
        @Override
        public Student checkUser(String num, String password) {
            return dao.selectStudentLogin(num,password);
        }
    
        @Override
        public Integer savaStudent(Student student) {
            return dao.insertStudent(student);
        }
    
    }

--------------------

### 六、消除StudentServiceImpl中的异常——>创建Dao层(需要写jdbc工具类) ###

> 其实到这里就已经很清晰了，是一个很清楚的三层架构

#### IStudentDao接口 ####

package linjie.com.dao;
    
    import linjie.com.beans.Student;
    
    public interface IStudentDao {
    
        Student selectStudentLogin(String num, String password);
    
        Integer insertStudent(Student student);
    
    }

#### StudentDaoImpl实现类 ####

> 到这里要注意，Dao层是要做什么的，是要与数据库来取得联系的，所以，这里应该先定义一个jdbc工具类，再写Dao层实现类

##### jdbcUtil.java #####

package linjie.com.utils;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    public class jdbcUtil {
        //加载DB驱动
        static {
                try {
                    Class.forName("com.mysql.jdbc.Driver");
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                }
        }
    
        private static Connection conn;
    
        //获取Connection对象
        public static Connection getConnection() throws SQLException {
                String url="jdbc:mysql://localhost:3306/sms";
                String user="root";
                String password="1111";
                if(conn==null || conn.isClosed()) {
                    conn=DriverManager.getConnection(url,user,password);
                }
                return conn;
        }
    
        //关闭资源
        public static void close(Connection conn,Statement stmt,ResultSet rs) throws SQLException {
                if(conn!=null && !conn.isClosed()) {
                    conn.close();
                }
                if(stmt!=null && !stmt.isClosed()) {
                    stmt.close();
                }
                if(rs!=null && !rs.isClosed()) {
                    rs.close();
                }
        }
    }

##### StudentDaoImpl实现类 #####

package linjie.com.dao;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    import linjie.com.beans.Student;
    import linjie.com.utils.jdbcUtil;
    
    public class StudentDaoImpl implements IStudentDao {
        private Connection conn;
        private Statement stmt;
        private PreparedStatement ps;
        private ResultSet rs;
    
        @Override
        public Student selectStudentLogin(String num, String password) {
            Student student=null;
            try {
                conn = jdbcUtil.getConnection();
                String sql = "select * from student where num=? and password=? ";
                ps = conn.prepareStatement(sql);
                ps.setString(1, num);
                ps.setString(2, password);
                rs=ps.executeQuery();
                if(rs.next()) {
                    student = new Student();
                    student.setId(rs.getInt("id"));
                    student.setNum(rs.getString("num"));
                    student.setName(rs.getString("name"));
                    student.setPassword(rs.getString("password"));
                    student.setAge(rs.getInt("age"));
                    student.setScore(rs.getDouble("score"));
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                try {
                    jdbcUtil.close(conn, ps, rs);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
    
            return student;
        }
    
        @Override
        public Integer insertStudent(Student student) {
            Integer id =null;
            try {
                conn = jdbcUtil.getConnection();
                String sql="insert into student(num,password,name,age,score) values(?,?,?,?,?)";
                ps=conn.prepareStatement(sql);
                ps.setString(1, student.getNum());
                ps.setString(2, student.getPassword());
                ps.setString(3, student.getName());
                ps.setInt(4, student.getAge());
                ps.setDouble(5, student.getScore());
    
                ps.executeUpdate();
    
                sql="select @@identity newID";
                ps = conn.prepareStatement(sql);
                rs = ps.executeQuery();
                if(rs.next()) {
                    id = rs.getInt("newID");
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                try {
                    jdbcUtil.close(conn, ps, rs);
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            return id;
        }
    
    }

--------------------

### 七、register.jsp创建 ###

> 登录差不多实现了，下面是注册功能，和登录差不多

<%@ page language="java" contentType="text/html; charset=UTF-8"
        pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>SMS注册页面</title>
    </head>
    <body>
        ${message }<br>
        <form action="${pageContext.request.contextPath }/registerServlet" method="POST">
            学号：<input type="text" name="num"/><br>
            密码：<input type="password" name="password"/><br>
            姓名：<input type="text" name="name"/><br>
            年龄：<input type="text" name="age"/><br>
            成绩：<input type="text" name="score"/><br>
            <input type="submit" value="注册">
        </form>
    </body>
    </html>

--------------------

### 八、ToRegisterServlet ###

> 在登录页面跳转到注册页面的时候，因为涉及到跳转，如果是严格按照MVC的话，需要创建一个servlet，然后在servlet中重定向或请求转发到注册页面，也可以不严格的直接跳转注册页面

--------------------

### 九、RegisterServlet ###

package linjie.com.servlets;
    
    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;
    
    import linjie.com.beans.Student;
    import linjie.com.service.IStudentService;
    import linjie.com.service.StudentServiceImpl;
    
    
    public class RegisterServlet extends HttpServlet {
    
        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //解决中文乱码
            request.setCharacterEncoding("UTF-8");
    
            //1、获取表单参数
            String num = request.getParameter("num");
            String password = request.getParameter("password");
            String name = request.getParameter("name");
            String ageStr=request.getParameter("age");
            String scoreStr = request.getParameter("score");
    
            Integer age = Integer.valueOf(ageStr);
            Double score = Double.valueOf(scoreStr);
    
            //创建student对象
            Student student = new Student(num,name,age,score);
            student.setPassword(password);
    
            //创建service对象
            IStudentService service = new StudentServiceImpl();
            //调用service对象的saveStudent()方法，将数据写入DB
            Integer id = service.savaStudent(student);
    
            //写入失败
            if(id == null) {
                HttpSession session = request.getSession();
                session.setAttribute("message", "没有注册成功");
                response.sendRedirect(request.getContextPath()+"/register.jsp");
            }
            //写入成功
            response.sendRedirect(request.getContextPath()+"/login.jsp");
    
    
        }
    
    }

### 十、 ###

> 然后继续是service层、Dao层的使用，因为上述代码已经包含register的相关代码，这里不多做阐述了。

### 十一、总结 ###

#### 1、代码并不难，但是主要是理解了MVC+三层架构具体是如何应用的 ####

#### 2、在开发这个简单的项目过程中，其实出现了很多问题，比如不小心把sql文件给Build path了，结果半天没弄出来哪错了。还有就是版本的问题 ####

**源码我已经放到github了，可自行下载**  
[https://github.com/ash-ali/SMS\_LR][https_github.com_ash-ali_SMS_LR]

[https_blog.csdn.net_w_linux_article_details_79919523]: https://blog.csdn.net/w_linux/article/details/79919523
[70]: /images/20220527/13500761c8e64c5a9459e8fbcdadd33a.png
[70 1]: /images/20220527/ef8ffbc7724f4068a457a6451169863b.png
[https_github.com_ash-ali_SMS_LR]: https://github.com/ash-ali/SMS_LR