dao层

dao全称 data access object,即数据连接层，也叫持久层，是数据库和web服务器的连接层。

包含两个基本java文件，一个文件是专门写接口，另一个是写接口的实现，专门写接口程序为了方便contraller调用。

接口程序：

package dao;
import java.util.List;
import entity.Student;

public interface StuDao {
    public List <Student> selAllStu();
    public void insertStu(Student stu);
    public void delStu(String num);
}

接口实现：

package dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import entity.Student;

public class StuDaoImp implements StuDao { // https://zhidao.baidu.com/question/355976494.html
    public List <Student> selAllStu(){
        List <Student> list = new <String> ArrayList();
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");//加载驱动
            con = DriverManager.getConnection("jdbc:oracle:thin:@//172.16." , "" , "" );//建立连接
            st = con.createStatement();        //获取Statement对象
            rs = st.executeQuery("select * from tb_students");
            while(rs.next()){
                Student stu = new Student();
                stu.setNum(rs.getString("num"));
                stu.setName(rs.getString("name"));
                stu.setSex(rs.getString("sex"));
                stu.setAge(rs.getInt("age"));
                list.add(stu);
            }
            
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally{
            try {
                if(rs != null)rs.close();
                if(st != null)st.close();
                if(con != null)con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return list;
    }
    public void insertStu(Student stu){
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        String sql = "insert into tb_students (num,name,sex,age) values('"+stu.getNum()+"','"+stu.getName()+"','"+stu.getSex()+"',"+stu.getAge()+")";
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");//加载驱动
            con = DriverManager.getConnection("jdbc:oracle:thin:@//172.16." , "" , "" );//建立连接
            st = con.createStatement();        //获取Statement对象
            st.execute(sql);    
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally{
            try {
                if(rs != null)rs.close();
                if(st != null)st.close();
                if(con != null)con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
    }
    public void delStu(String num){
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        String sql = "delete from tb_students where num='"+num+"'";
        try {
            Class.forName("oracle.jdbc.driver.OracleDriver");//加载驱动
            con = DriverManager.getConnection("jdbc:oracle:thin:@//172.16." , "" , "" );//建立连接
            st = con.createStatement();        //获取Statement对象
            st.execute(sql);    
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally{
            try {
                if(rs != null)rs.close();
                if(st != null)st.close();
                if(con != null)con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}