一、报错信息
mybaits查询报错：
Tue Oct 20 15:46:34 CST 2020 There was an unexpected error (type=Internal Server Error, status=500).nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException:
Failed to obtain JDBC Connection; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
### The error may exist in file [D:\project\mybatis\target\classes\mapper\TruckInfoMapper.xml]
### The error may involve com.example.mybatis.cache.dao.mapper.TruckInfoMapper.getTruckInfo
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException:
Failed to obtain JDBC Connection; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
二、问题排查
从报错信息上预测是JDBC连接获取失败导致。因此，首先查询mysql版本和jdbc版本。
1、查询mysql版本
Mysql版本为8.0.19。
2、查询JDBC版本
JDBC版本为5.1.39。
3、问题结论
Mysql与JDBC版本不一致，兼容性问题导致JDBC连接获取失败。
三、解决方案
1、升级JDBC版本，5.1.39--->8.0.12。 2、修改数据库驱动， driver-class-name: com.mysql.cj.jdbc.Driver
