I hope I don't ask a stupid question.
Hibernate recommend seperating object id and business key,for example,
a product has a auto-generate id and a unique product serial No. Here is the question:
I and my colleagues are beginners for hibernate,in a recent project,I stick to the foreign key is referenced by id(auto-generate id),but one of my colleagues argues that we should use the business key(product serial No.) for FK. Of course,hibernate allow both,could you give me some valuable suggestion?thanks very much!

Always use the surrogate key for primary and foreign key constraints. Thats the point, really. The purpose of the surrogate key is to allow the separation of database internal semantics (PK and FK constraints) from external business semantics.

Thanks, christian!Your answer comes just in time,by the way I am very glad that you understand my shabby English.