基于MVC+三层架构实现—SMS

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

下面是开发全过程

项目目录

这里写图片描述

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

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IDprivate 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/getterspublic 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SessionHttpSession 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.jspsession.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StudentInteger 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();}@Overridepublic Student checkUser(String num, String password) {return dao.selectStudentLogin(num,password);}@Overridepublic 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;@Overridepublic 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;}@Overridepublic 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

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;public class ToRegisterServlet extends HttpServlet {protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.sendRedirect(request.getContextPath()+"/register.jsp");}}

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DBInteger 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");}}