Hibernate查询：Set是否包含某个Object？

I have two Hibernate data object. The first is a User (with unique id, username etc.) and the second is the class Collaborateable. Between this two there is a n-to-m relation (implementet with Sets). That means, a User works on many Collaborateables and a Collaborateable has many users. In addition a Collaborateable has exactly one User as owner.I have two Hibernate data object. The first is