StuDAO

package com.svse.dao;

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

import com.svse.entity.StuEntity;

public class StuDAO {
    // 全查询
    public List<StuEntity> getAll() {
        List<StuEntity> ar = new ArrayList<StuEntity>();
        try {
            String driver = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql://localhost:3306/test";
            String user = "root";
            String password = "root";
            Connection  conn=null;
            Class.forName(driver);
            conn=DriverManager.getConnection(url, user, password);
            
            String sql="select *  from stuinfo";
            PreparedStatement pre=conn.prepareStatement(sql);
            ResultSet rs=pre.executeQuery();
            while(rs.next())
            {
                int sid=rs.getInt("sid");
                String sname=rs.getString("sname");
                String spsw=rs.getString("spsw");
                
                StuEntity s=new StuEntity();
                s.setSid(sid);
                s.setSname(sname);
                s.setSpsw(spsw);
                
                ar.add(s);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
        return ar;
    }

    // 查询一个对象
    public StuEntity getOne(int sid) {
        StuEntity stu = new StuEntity();
        try {
            String driver = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql://localhost:3306/test";
            String user = "root";
            String password = "root";
            Connection  conn=null;
            Class.forName(driver);
            conn=DriverManager.getConnection(url, user, password);

            String sql="select *  from stuinfo where sid=?";
            PreparedStatement pre=conn.prepareStatement(sql);
            pre.setInt(1, sid);
            ResultSet rs=pre.executeQuery();
            while(rs.next())
            {
                String sname=rs.getString("sname");
                String spsw=rs.getString("spsw");
                
                stu.setSid(sid);
                stu.setSname(sname);
                stu.setSpsw(spsw);
            }
            
        } catch (Exception e) {
            e.printStackTrace();
        }
        return stu;
    }

    // 修改
    public void updateStu(StuEntity stu) {
        try {
            String driver = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql://localhost:3306/test";
            String user = "root";
            String password = "root";
            Connection  conn=null;
            Class.forName(driver);
            conn=DriverManager.getConnection(url, user, password);

            String sql="update stuinfo set sname=?,spsw=? where sid=?";
            PreparedStatement pre=conn.prepareStatement(sql);
            pre.setString(1,stu.getSname());
            pre.setString(2,stu.getSpsw());
            pre.setInt(3,stu.getSid());
            pre.executeUpdate();
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

StuEntity

package com.svse.entity;

public class StuEntity {

    private int sid;
    private String sname;
    private String spsw;

    public int getSid() {
        return sid;
    }

    public void setSid(int sid) {
        this.sid = sid;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public String getSpsw() {
        return spsw;
    }

    public void setSpsw(String spsw) {
        this.spsw = spsw;
    }

}

Test

package com.svse.test;

import java.util.List;
import java.util.Scanner;

import com.svse.dao.StuDAO;
import com.svse.entity.StuEntity;

public class Test {
    
    public static void main(String[] args) {
        StuDAO dao=new StuDAO();
        System.out.println("\t\t\t武汉光谷职业学院学生信息");
        System.out.println("以下是全查询学生信息:");
        List<StuEntity> ar=dao.getAll();
        for (StuEntity stuEntity : ar) {
            System.out.println(stuEntity.getSid()+"\t"+stuEntity.getSname()+"\t"+stuEntity.getSpsw());
        }
        System.out.println("请输入你要修改的学生的编号：");
        Scanner sa=new Scanner(System.in);
        int sid=sa.nextInt();
        //一个指定的学生的信息
        StuEntity s=dao.getOne(sid);
        System.out.println("以下是你要修改的学生的信息：");
        System.out.println(s.getSid()+"\t"+s.getSname()+"\t"+s.getSpsw());
        //下面是填写要修改的信息
        System.out.println("请输入要修改的姓名：");
        String sname=sa.next();
        System.out.println("请输入要修改的密码：");
        String spsw=sa.next();
        //封装
        StuEntity ss=new StuEntity();
        ss.setSid(sid);
        ss.setSname(sname);
        ss.setSpsw(spsw);
        //调用 修改
        dao.updateStu(ss);
        System.out.println("修改成功！");
    }

}