org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions

保存出错：
org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
    at org.hibernate.collection.AbstractPersistentCollection.setCurrentSession(AbstractPersistentCollection.java:432)
    at org.hibernate.event.def.OnUpdateVisitor.processCollection(OnUpdateVisitor.java:66)
    at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:124)
    at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:84)
    at org.hibernate.event.def.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:78)
    at org.hibernate.event.def.AbstractVisitor.process(AbstractVisitor.java:146)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:316)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:246)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:112)
    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:535)
    at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:527)
    at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:523)