解决 mysql5 升级到mysql8 ，mybatis连接失败

转载: https://blog.csdn.net/AOBO516/article/details/93370637#%E5%8D%87%E7%BA%A7MySQL%E9%A9%B1%E5%8A%A8mysql-connector-java%E5%8D%87%E7%BA%A7%E5%88%B08.0.X%E7%89%88%E6%9C%AC

解决过程：

1 升级MySQL驱动mysql-connector-java升级到8.0.X版本

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.16</version> </dependency>

2 修改配置中的驱动类 驱动类变了，原来是由原来的com.mysql.jdbc.Driver 改为 com.mysql.cj.jdbc.Driver

不修改会影响性能，启动过程中有告警： Loading class com.mysql.jdbc.Driver'. This is deprecated. The new driver class iscom.mysql.cj.jdbc.Driver’. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

3 jdbc_url上的时区变为必须配置，否则会启动报错 在原来的 jdbc_url的最后加上 &serverTimezone=GMT

如：

jdbc:mysql://localhost:3306/dbname??useUnicode=true&characterEncoding=UTF-8&useSSL=true&serverTimezone=GMT&autoReconnect=true&failOverReadOnly=false

如果不加，报错：

Caused by: com.mysql.cj.exceptions.InvalidConnectionAttributeException: The server time zone value '�й���׼ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.