druid连接池异常

在从excel导入10W条数据到mysql中时，运行一段时光就会抛这个异常，衔接池问题

org.springframework.transaction.CannotCreateTransactionException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.TransactionException: JDBC begin failed:
Caused by: java.sql.SQLException: connection holder is null
	at com.alibaba.druid.pool.DruidPooledConnection.checkState(DruidPooledConnection.java:1085)
	at com.alibaba.druid.pool.DruidPooledConnection.getMetaData(DruidPooledConnection.java:825)
	at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:285)

or