之前一直在虚拟机本地调试，加内网转发，今天上传到阿里云报了一个错误，没找到问题，
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: Connections could not be acquired from the underlying database!↵### The error may exist in file [/home/apache-tomcat-8.0.52/webapps/o2o/WEB-INF/classes/mapper/ShopDao.xml]↵### The error may involve com.imooc.o2o.dao.ShopDao.queryShopList↵### The error occurred while executing a query↵### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database

感觉是数据库链接错误，我线上数据库版本是5.6.44。。但是本地版本是mysql5.7.27(能连上)

我写了个远程链接数据库的测试类，debug也能连上，好像不是什么驱动问题，如果是驱动问题，为什么远程debug也能连上呢？

mark:之前折腾数据库版本换过mysq8.xx，c3pO驱动版本也重新配置过但是还是链接不上