1.jdbc报错：java.lang.ClassNotFoundException: com.mysql.jdbc.driver
严重: Servlet.service() for servlet [daleystore-manager] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: com.mysql.jdbc.driver### The error may exist in com/daleystore/mapper/TbItemMapper.xml
### The error may involve com.daleystore.mapper.TbItemMapper.selectByExample
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: com.mysql.jdbc.driver] with root cause
java.lang.ClassNotFoundException: com.mysql.jdbc.driver
起初我以为是框架的错误，从头到尾检查了一遍，最后才发现是.properties的配置文件中出错。
如果你也出现这种错误，百分之90%是这里写错了，有可能是用户名密码写错，
这里注意：在写username，password的时候要加上前缀 jdbc. 如 jdbc.username ,否则会认为是JVM系统环境变量的username，password同理。
也有可能是其他一些属性出错。
我这里的问题是jdbc.driver=com.mysql.jdbc.Driver的driver小写了。
