org.hibernate.MappingException：无法确定类型：java.util.Set，在表：USERS，对于列：[org.hibernate.mapping.Column（invoices）]

I have a problem that Hibernate is unable to determine the type for Set at the table USERS. I am trying to create a foreign key of table INVOICES through one-to-many relationship. One User can generate many Invoices. My User.java is given below. I have a problem that Hibernate is unable to de