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

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;
    }
    

}

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)+"
");
            }
            System.out.println(sb.toString());
            
        }catch(Exception e)
        {
            e.printStackTrace();
        }
        
    }

}

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;
    

}

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;
    }
    
}

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;

}

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;
    }

}

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);
    
        
    }

}

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。