Hibernate 执行十万级数据批量操作时遇到的错误 求大神！

同步批量执行SQL插入语句 30分钟左右后报错信息如下：

[ERROR] 2019-04-28 13:24:28,652 org.c.event.def.AbstractFlushingEventListener - Could not synchronize database state with session org.hibernate.exception.GenericJDBCException: could not insert: [com.eplugger.netSearch.paper.entity.NetSearchPaper]

[ERROR] 2019-04-28 13:24:28,743 org.hibernate.transaction.JDBCTransaction - Could not toggle autocommit java.sql.SQLException: connection holder is null

Caused by: java.sql.SQLException: connection holder is null at com.alibaba.druid.pool.DruidPooledConnection.checkStateInternal(DruidPooledConnection.java:1140) at com.alibaba.druid.pool.DruidPooledConnection.checkState(DruidPooledConnection.java:1131) at com.alibaba.druid.pool.DruidPooledConnection.prepareStatement(DruidPooledConnection.java:333) at org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:497) at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:94) at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:87) at org.hibernate.jdbc.AbstractBatcher.prepareBatchStatement(AbstractBatcher.java:218) at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2174) ... 139 more