远程连接MySQL时发现如下错误：
java.sql.SQLException: null, message from server: "Host '192.168.30.23' is not allowed to connect to this MySQL server"
解决方法：
进入MySQL的bin目录,执行如下代码：
mysql -u root -proot
mysql> user mysql;
mysql> update user set host = '%' where user = 'root';
mysql> flush privileges;
