在web中连接mysql时候，出现如下警告：
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.
在高版本的MySQL下连接数据库需要表示是否要连接SSL
解决办法：在连接数据库后面添加useSSL=false或者useSSL=true
如：
jdbc:mysql://localhost:3306/yuejuan?useSSL=false
