问题描述：
在mysql5.7版本，发现登录不了，找不到原因。有人说是驱动的问题，下载最新的驱动，问题得到解决！
问题解决：
下载最新mysql-jar驱动，传统版本最新mysql-jar驱动版本5.1.45，要下载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