HTTP Status 500 - 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: Connections could not be acquired from the underlying database! ### The error may exist in URL [jar:file:/D:/BaiduNetdiskDownload/eclipse/wk/.metadata/.plugins/org.eclipse.wst.server.core/tmp0/wtpwebapps/ocPortal/WEB-INF/lib/ocService-1.0.0-SNAPSHOT.jar!/com/online/college/core/consts/dao/ConstsSiteCarouselMapper.xml] ### The error may involve com.online.college.core.consts.dao.ConstsSiteCarouselDao.queryCarousels ### 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!

老师，都是按照视频配置为什么连不上数据库？