基于Java（MySQL数据库）的选课系统，简单易理解

 学生功能：

package com.dao;

import com.orm.Courses;
import com.orm.StuCou;
import com.orm.Students;
import com.util.BaseDAO;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class StudentDao extends BaseDAO {
    Connection con = null;
    PreparedStatement pst = null;
    ResultSet rs = null;



    //学生选课
    public void chooseCourses(int stuID,int couID) throws Exception {
        StuCou sc=new StuCou();
        con=BaseDAO.getCon();
        String sql="insert into stucourses(stuID,couID) values(?,?)";
        try {
            pst=con.prepareStatement(sql);
            pst.setInt(1, stuID);
            pst.setInt(2,couID);
            int result=pst.executeUpdate();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
    //查看全部课程
    public void SClookCourse() throws Exception {
        con=BaseDAO.getCon();

        try {
            String sql="select * from courses";
            pst=con.prepareStatement(sql);
            rs=pst.executeQuery();
            int index=0;
            while(rs.next())
            {
                 Courses cou=new Courses();
                int couID = rs.getInt("couID");//获取集合第1行，deviceid 这一列的值
                String couName = rs.getString("couName");//获取集合第1行 devicename 列的值
                String couTeacher = rs.getString("couTeacher");//获取集合第1行 devicetype 列的值
                System.out.println(couID + " " + couName + " " +  couTeacher );


            }
             con.close();
            pst.close();
            rs.close();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }
    //查询总成绩以及平均成绩
    public void lookGrade() throws Exception{
        con=BaseDAO.getCon();
        try{
            String sql="SELECT stuID,SUM(grade),AVG(grade) FROM grade GROUP BY stuID;";
            pst=con.prepareStatement(sql);
            rs=pst.executeQuery();
            int index=0;
            while(rs.next()){
                int stuID=rs.getInt("stuID");
                int sum=rs.getInt("sum(grade)");
                double avg=rs.getInt("avg(grade)");
                System.out.println("学号"+" "+ "总成绩"+" " +"平均成绩");
                System.out.println(stuID+"     "+sum+"     "+avg+"   ");

            }
        }catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

             }

 

 教师功能（部分代码）：

package com.dao;

import com.orm.Courses;
import com.orm.StuCou;
import com.orm.Students;
import com.util.BaseDAO;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDao extends BaseDAO {
    Connection con = null;
    PreparedStatement pst = null;
    ResultSet rs = null;


    //增加学生信息
    public int add(Students stu) throws Exception {
        //Students stu=new Students();
        int result=0;
        con=BaseDAO.getCon();
        String sql="insert into students(stuID,stuName,stuYear,StuNumber,stuSex) values(?,?,?,?,?)";
        try {
            pst=con.prepareStatement(sql);
            pst.setInt(1, stu.getStuID());
            pst.setString(2,stu.getStuName());
            pst.setInt(3, stu.getStuYear());
            pst.setString(4,stu.getStuNumber());
            pst.setString(5,stu.getStuSex());
            result=pst.executeUpdate();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        return result;
    }
    //删除学生
    public int del(int stuID) throws Exception {

        int result=0;
        con=BaseDAO.getCon();
        String sql="delete from students where stuID=?";
        try {
            pst=con.prepareStatement(sql);
            pst.setInt(1, stuID);
            result=pst.executeUpdate();

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return result;
    }
    //修改学生
    public int update(Students stu) throws Exception {

        int result=0;
        boolean flag = false;
        try {
        con=BaseDAO.getCon();
        String sql="update students set stuName=?,stuYear=?,stuNumber=?,stuSex=? where stuID=?";
            pst=con.prepareStatement(sql);
            pst.setString(1,stu.getStuName());
            pst.setInt(2,stu.getStuYear());
            pst.setString(3,stu.getStuNumber());
            pst.setString(4,stu.getStuSex());
            pst.setInt(5,stu.getStuID());
            if(pst.executeUpdate() !=0){
                flag=true;
            }
            pst.close();
            con.close();
            //result=pst.executeUpdate();
        //System.out.println(stu.getStuID());
        System.out.println("修改完成！");




        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return result;
    }
    //查找全部学生
    public List<Students> queryAll() throws Exception {
        List<Students> list=new ArrayList<Students>();
        con=BaseDAO.getCon();
        String sql="select * from students";
        try {
            pst=con.prepareStatement(sql);
            rs=pst.executeQuery();
            while(rs.next())
            {
                Students stu= new Students();
                stu.setStuID(rs.getInt(1));
                stu.setStuName(rs.getString(2));
                stu.setStuYear(rs.getInt(3));
                stu.setStuNumber(rs.getString(4));
                stu.setStuSex(rs.getString(5));
                list.add(stu);

                System.out.println(stu.getStuID()+" "+stu.getStuName()+" "+stu.getStuYear()+" "+stu.getStuNumber()+" "+stu.getStuSex());
            }


        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return list;
    }
    //查找指定学生
    public void queryStudentById(int stuID) throws Exception {
        Students stu=new Students();
        con=BaseDAO.getCon();
        String sql="select * from students where stuID=?;";
        try {
            pst=con.prepareStatement(sql);
            pst.setInt(1,stuID);
            rs=pst.executeQuery();
            if(rs.next())
            {
                stu.setStuID(rs.getInt("stuID"));
                stu.setStuName(rs.getString("stuName"));
                stu.setStuYear(rs.getInt("stuYear"));
                stu.setStuNumber(rs.getString ("stuNumber"));
                stu.setStuSex(rs.getString("stuSex"));
                System.out.println(stu.getStuID()+""+stu.getStuName()+""+stu.getStuYear()+""+stu.getStuNumber()+""+stu.getStuSex());
            }

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        //return stu;
    }