1.UserDao接口

主要规范UserDaoImp的方法，具体代码如下：

package dao;

import entity.user;

/**
 * @author :LiuYihong
 * @Description :
 * @date : 2022/5/3 12:57
 * @Version 1.0
 */
public interface UserDao {
    public  void addUsers(user user);

    public void deleteUsers(user user);

    public void updateUsers(user user);

}

2.UserDaoImp实现类

实现与数据库连接的增、删、改方法，这里会用到前面写的连接工具类，用户实体类，重要的是preparestatement方法，里面填写预编译的sql语句，具体参数是从前端输入标签中获取的。

package dao.imp;

import dao.UserDao;
import entity.user;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import static util.baseDao.getConnections;

/**
 * @author :LiuYihong
 * @Description :
 * @date : 2022/5/3 13:51
 * @Version 1.0
 */
public class UserDaoImp implements UserDao {

    @Override
    public void addUsers(user user) {
        Connection con = null;
        PreparedStatement pp = null;
        try {
            //得到数据库连接
            con=getConnections();
//            给pp赋值
            pp = con.prepareStatement("INSERT INTO users (uid,uname,upwd) VALUES (?,?,?)");
//           在预编译语句中填入相应的值
            pp.setInt(1,user.getUid());
            pp.setString(2,user.getUname());
            pp.setString(3,user.getUpwd());
//            执行更新操作
            pp.executeUpdate();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally{
//            关闭资源
        }
    }
    @Override
    public void deleteUsers(user user) {
        Connection con = null;
        PreparedStatement pp = null;
        try {
            con=getConnections();
            pp = con.prepareStatement("DELETE FROM users WHERE id=?");
            pp.setInt(1, user.getUid());
            pp.executeUpdate();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }
    @Override
    /**
     * 更新操作还未完善
     */
    public void updateUsers(user user) {
        Connection con = null;
        PreparedStatement pp = null;
        try {
            con=getConnections();
            pp = con.prepareStatement("UPDATE users SET `uid`=?,SET `uname`=?,SET `upwd`=?, WHERE id=?");
            pp.setInt(4,user.getOid());
            pp.setString(2,user.getUname());
            pp.setString(3,user.getUpwd());
            pp.setInt(1,user.getUid());
            pp.executeUpdate();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }

    }
}