問題描述：
在mysql5.7版本，發現登錄不了，找不到原因。有人說是驅動的問題，下載最新的驅動，問題得到解決！
問題解決：
下載最新mysql-jar驅動，傳統版本最新mysql-jar驅動版本5.1.45，要下載mysql-jar-8.0.15
MySQL Connector/J is the official JDBC driver for MySQL. MySQL Connector/J 8.0 is compatible with all MySQL versions starting with MySQL 5.5. Additionally, MySQL Connector/J 8.0 supports the new X DevAPI for development with MySQL Server 8.0.
https://dev.mysql.com/downloads/connector/j/
https://mvnrepository.com/artifact/mysql/mysql-connector-java/8.0.15
http://central.maven.org/maven2/mysql/mysql-connector-java/8.0.15/mysql-connector-java-8.0.15.jar