1.首先：jdbc所需要的maven依赖
2.java获取到数据库的连接.
jdbc工具类

public final  class jdbcUtil  { 
    private static final String URL = "jdbc:mysql://120.25.227.234:3306/user?useSSL=false";
    private static final String USER = "user";
    private static final String PASSWORD = "root";

    private static Connection connection = null;

    static { 

        try { 
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) { 
            e.printStackTrace();
        }

        try { 
            connection = (Connection) DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (SQLException throwables) { 
            throwables.printStackTrace();
        }

    }

    public static Connection getConnection(){ 
        return connection;
    }

}

工具类的使用方法：

public class userDaoImpl implements userDao{ 
	//直接获取链接
    Connection conn = jdbcUtil.getConnection();


    public boolean getUserInstance(String username, String password) throws Exception { 
        String sql = "select * from user where username = ? and password = ?";
        PreparedStatement preparedStatement = conn.prepareStatement(sql);
        preparedStatement.setString(1,username);
        preparedStatement.setString(2,password);

        ResultSet resultSet = preparedStatement.executeQuery();

        if(!resultSet.next()){ 
            return false;
        }else { 
            return true;
        }
    }
}