com.mysql.jdbc.Driver 是 mysql-connector-java 5中的，
com.mysql.cj.jdbc.Driver 是 mysql-connector-java 6中的
1、JDBC连接Mysql5 com.mysql.jdbc.Driver:
driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=
2、JDBC连接Mysql6 com.mysql.cj.jdbc.Driver， 需要指定时区serverTimezone:
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?serverTimezone=UTC&?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=
在设定时区的时候，如果设定serverTimezone=UTC，会比中国时间早8个小时，如果在中国，可以选择Asia/Shanghai或者Asia/Hongkong，例如：
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?serverTimezone=Shanghai&?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=
备注：
I、如果mysql-connector-java用的6.0以上的，如下：
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>6.0.6</version>
</dependency>
但是你的driver用的还是com.mysql.jdbc.Driver，就会报错：
Loading class 'com.mysql.jdbc.Driver'. This is deprecated. The new
driver class is 'com.mysql.cj.jdbc.Driver'.
The driver is automatically registered via the SPI
and manual loading of the driver class is generally unnecessary.
此时需要把com.mysql.jdbc.Driver 改为com.mysql.cj.jdbc.Driver
II、还有一个警告：
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 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.
不推荐不使用服务器身份验证来建立SSL连接。
如果未明确设置，MySQL 5.5.45+, 5.6.26+ and 5.7.6+版本默认要求建立SSL连接。
为了符合当前不使用SSL连接的应用程序，verifyServerCertificate属性设置为’false’。
如果你不需要使用SSL连接，你需要通过设置useSSL=false来显式禁用SSL连接。
如果你需要用SSL连接，就要为服务器证书验证提供信任库，并设置useSSL=true。
SSL – Secure Sockets Layer（安全套接层）
MySql驱动8.0.11版本的一些使用注意事项
1>解决java.sql.SQLException: The server time zone value '???ú±ê×??±??' is unrecognized or represents more than one time zone.
添加格式：
?serverTimezone=GMT%2B8;
使用的数据库是MySQL，驱动是8.0.11，这是由于数据库和系统时区差异所造成的，在jdbc连接的url后面加上serverTimezone=GMT即可解决问题，如果需要使用gmt+8时区，需要写成GMT%2B8，否则会被解析为空。再一个解决办法就是使用低版本的MySQL jdbc驱动，5.1.28不会存在时区的问题。
2>解决：Fri May 18 15:00:19 CST 2018 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 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.
在后面加入：useSSL=false
3>解决：Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
不能这样 driverClass="com.mysql.jdbc.Driver" 写了，应该修改成 driverClass="com.mysql.cj.jdbc.Driver"
最终如下：
<jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
connectionURL="jdbc:mysql://localhost:3306/springmvc?serverTimezone=GMT%2B8&useSSL=false"
userId="root" password="root">
</jdbcConnection>
还有一些其他的可能未总结到
参考资料:
https://blog.csdn.net/m0_37520980/article/details/80364884
https://blog.csdn.net/superdangbo/article/details/78732700
