学习慕课上的一个项目，使用的是Spring+Mybatis+c3po 学习搭建框架。

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:

Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!

The error may exist in file [E:\ecplisepro\schoolShop\target\classes\mapper\AreaDao.xml]

The error may involve com.imooc.o2o.dao.AreaDao.queryArea

The error occurred while executing a query

Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!

网上搜了终于找到了答案，mysql-connector-java.jar 我引入 的jar包问题，所以我总结了，在入门学习时大家对版本的要重视，要不然出的错很无厘头，对于刚开始学习的自信心打击很大，我也是卡了好久，才自己解决了这些问题，
于是我果断换回了以前的版本，

修改了POM文件

	<dependency>
		<groupId>mysql</groupId>
		<artifactId>mysql-connector-java</artifactId>
		<version>5.1.37</version>
	</dependency>

JDBC连接Mysql 8.0.12版本的几个注意事项
改了之后通过了单元测试

看见单元测试红色长条变成了绿色，我笑了，虽然很low终究是入门了。