报错信息类似这样：
Wed May 27 14:15:54 CST 2020 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 se.........
解决方法：
在url值中加上useSSL=false。
url值应该改为：jdbc:mysql://localhost:3306/supermarket?useSSL=false&serverTimezone=UTC
