web初学之MVC

时间：2023-03-08 21:37:27
web初学之MVC

之前对JavaEE的MVC模式有些许了解，但一直没有很好的掌握，在读代码时候也很模糊不清。因此对MVC又通过各种资料有了全面的理解。

一．首先，需要从了解JavaEE技术开始。JavaEE技术在设计程序时，一般会把程序的结构设计成三层。

●表示层—用户界面和用于生成界面的代码组成。

●中间层—系统的业务和功能代码。

●数据层—完成存储数据库的数据和对数据进行封装。

基于这种程序结构，有了MVC。M即为数据层，包括各种JavaBean以及数据库工具。V即为表示层，通常为Jsp或HTML页面，显示在客户端。C即为中间层，一般为Web层的Servlet组件，由它来处理客户端的各种请求以及数据。

二．MVC的简单应用:

1）Eclipse中的创建项目，项目名chapter11

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" alt="" />

2）模型实体Student

 package com.chapter11.bean;

 import java.sql.Date;

 public class Student {

     private int id;

     private String name;

     private Date birthday;

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public Date getBirthday() {

         return birthday;

     }

     public void setBirthday(Date birthday) {

         this.birthday = birthday;

     }

 }

JavaBean

3）数据库连接工具JdbcUtil

 package com.chapter11.util;

 import java.sql.Connection;

 import java.sql.DriverManager;

 import java.sql.ResultSet;

 import java.sql.Statement;

 public class JdbcUtil {

     static{

         try{

             Class.forName("com.mysql.jdbc.driver");

         }catch(Exception e)

         {

             e.printStackTrace();

         }

     }

     public static Connection getConnection()

     {

         Connection con=null;

         try{

             con=DriverManager.getConnection("jdbc:mysql://localhost:3306/sms","root","hanzhao1024");

         }catch(Exception e){

             e.printStackTrace();

         }

         return con;

     }

     public static void release(Connection con,Statement stmt,ResultSet rs)

     {

         try{

             if(rs!=null)

             {

              rs.close();

             }

         }catch(Exception e)

         {

             e.printStackTrace();

             }

         try{

             if(stmt!=null)

             {

              stmt.close();

             }

         }catch(Exception e)

         {

             e.printStackTrace();

             }

         try{

             if(con!=null)

             {

              con.close();

             }

         }catch(Exception e)

         {

             e.printStackTrace();

             }

     }

     public static void printRs(ResultSet rs)

     {

         StringBuffer sb=new StringBuffer();

         try{

             while(rs.next())

             {

                 sb.append("id="+rs.getInt(1)+"");

                 sb.append("name="+rs.getString(2)+"\n");

             }

             System.out.println(sb.toString());

         }catch(Exception e)

         {

             e.printStackTrace();

         }

     }

 }

JdbcUtil

4）数据访问层接口StudentDao

 package com.chapter11.dao;

 import java.sql.SQLException;

 import java.util.List;

 import java.sql.SQLException;

 import com.chapter11.bean.Student;

 public interface StudentDao {

     public void insertStudent(Student stu)throws SQLException;

     public List queryAllStudents()throws SQLException;

 }

StudentDao

5）数据访问层接口实现类StudentDaoImpl

 package com.chapter11.dao;

 import java.sql.Connection;

 import java.sql.PreparedStatement;

 import java.sql.ResultSet;

 import java.sql.SQLException;

 import java.util.ArrayList;

 import java.util.List;

 import com.chapter11.bean.Student;

 import com.chapter11.util.JdbcUtil;

 public class StudentDaoImpl implements StudentDao {

     Connection con=null;

     public StudentDaoImpl(Connection con)

     {

         this.con=con;

     }

     PreparedStatement pstmt=null;

     ResultSet rs=null;

     public void insertStudent(Student stu)throws SQLException

     {

         String sql="insert into student(name,birthday) value(?,?)";

         pstmt=con.prepareStatement(sql);

         pstmt.setString(1, stu.getName());

         pstmt.setDate(2, stu.getBirthday());

         pstmt.executeUpdate();

         JdbcUtil.release(null, pstmt, null);

     }

     public List queryAllStudents()throws SQLException

     {

         String sql="select*from student";

         List students=new ArrayList();

         pstmt=con.prepareStatement(sql);

         ResultSet rs=pstmt.executeQuery();

         while(rs.next())

         {

             Student stu=new Student();

             stu.setId(rs.getInt("id"));

             stu.setName(rs.getString("name"));

             stu.setBirthday(rs.getDate("birthday"));

             students.add(stu);

         }

         JdbcUtil.release(null, pstmt, null);

         return students;

     }

 }

StudentDaoImpl

6）增加和删除的业务服务层接口StudentService

package com.chapter11.service;

import java.sql.SQLException;

import java.util.List;

import com.chapter11.bean.Student;

public interface StudentService {

    public void addStudent(Student stu)throws SQLException;

    public List findAllStudent()throws SQLException;

}

StudentService

7）增加和删除的业务服务层接口StudentServiceImpl

 package com.chapter11.service;

 import java.sql.Connection;

 import java.sql.SQLException;

 import java.util.List; 

 import com.chapter11.bean.Student;

 import com.chapter11.dao.StudentDao;

 import com.chapter11.dao.StudentDaoImpl;

 import com.chapter11.util.JdbcUtil;

 public class StudentServiceImpl implements StudentService{

     public void addStudent(Student stu)throws SQLException

     {

         Connection con=JdbcUtil.getConnection();

         try{

             con.setAutoCommit(false);

             StudentDao sdao=new StudentDaoImpl(con);

             sdao.insertStudent(stu);

             con.commit();

         }catch(Exception e)

         {

             e.printStackTrace();

         }

     }

     public List findAllStudent()throws SQLException

     {

         Connection con=JdbcUtil.getConnection();

         List students=null;

         try{

             con.setAutoCommit(false);

             StudentDao sdao=new StudentDaoImpl(con);

             sdao.queryAllStudents();

             con.commit();

         }catch(Exception e)

         {

             e.printStackTrace();

         }

         return students;

     }

 }

StudentServiceImpl

8)Web层控制器Servlet

package com.chapter11.servlet;

import java.io.IOException;

import java.sql.Date;

import java.util.List;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletContext;

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 com.chapter11.bean.Student;

import com.chapter11.service.*;

@WebServlet("/SMSServletController")

public class SMSServletController extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public SMSServletController() {

        super();

    }

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

    this.doPost(request, response);

    }

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

        StudentService ss=new StudentServiceImpl();

        String path=request.getServletPath();

        path=path.substring(0,path.indexOf("."));

        if(path.equalsIgnoreCase("/sms/list"))

        {

            try

            {

                List students=ss.findAllStudent();

                request.setAttribute("students", students);

                forward("list.jsp",request,response);

            }catch(Exception e)

            {

                throw new ServletException("error when query!");

            }

        }else if(path.equalsIgnoreCase("/sms/add"))

        {

            request.setCharacterEncoding("UTF-8");

            String name=request.getParameter("name");

            String birthday=request.getParameter("birthday");

            Student student=new Student();

            student.setBirthday(Date.valueOf(birthday));

            student.setName(name);

            try{

                ss.addStudent(student);

                }catch(Exception e)

                {

                    e.printStackTrace();

                }

            response.sendRedirect(request.getContextPath()+"/sms/list.do");

            }

        }

    private void forward(String url, HttpServletRequest request,

            HttpServletResponse response)throws IOException,ServletException{

        ServletContext application=getServletContext();

        RequestDispatcher ds=application.getRequestDispatcher(url);

        ds.forward(request,response);

    }

}

Servlet

9）Web层表示页面

整个过程即为一个基本的MVC设计模式以及代码流程。在此还未解决的问题是最后的表示层页面显示，会在此后逐步解决。

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