一、DBConnection 类

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/** * @author: By yangbocsu * @date: 2021/10/6 10:10 * @description: 110.42.134.158:3306 "jdbc:mysql://110.42.134.158:3306/myemployees" */
public class DBConnection {
    private static String driver = "com.mysql.jdbc.Driver";
    private static String URL = "jdbc:mysql://localhost:3306/myemployees?useSSL=true";   //myemployees：要连接的数据库名
    private static String USER = "root";
    private static String PASSWORD = "123";

    //?useSSL=true 不加它会产生的问题，如下
// Wed Oct 06 11:20:14 CST 2021 WARN: Establishing SSL connection without server's identity verification is not recommended.
// According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set.
// For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'.
// You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.

    public static Connection getConnection()
    {
        Connection con = null;
        try
        {
            // DriverManager是类用来管理数据库中的所有驱动程序，调用它的静态方法可以getConnection(url,user,password)与数据库建立连接，
            // 连接成功会返回connection对象，后面的接口都会依赖于这个接口对象
            Class.forName(driver);  //加载驱动程序
            con = DriverManager.getConnection(URL,USER,PASSWORD);
            System.out.println("已经连接上myemployees数据库");
            return con;
        }
        catch (ClassNotFoundException | SQLException e)
        {
            System.out.println("连接失败了！！！！");
            e.printStackTrace();
        }
        return null;
    }
}

二、EmployeesMgr 类

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/** * @author: By yangbocsu * @date: 2021/10/6 10:27 * @description: */
public class EmployeesMgr {
    public static void main(String[] args) throws SQLException {
        DBConnection dbc = new DBConnection();
        Connection con = dbc.getConnection();

        //向数据库发送SQL语句 需要创建 Statement类对象
        Statement stmt = con.createStatement();
        ResultSet res = stmt.executeQuery("select * from employees;");
        res.next();
// while (res.next())
        {
            System.out.println(res.getString("email"));
        }

        con.close();
    }

}