The assigned primary key need to be modified。 How to do this?
Should I first delete the original record with original key and create a new one with the new key?

Yes

Thanks.

But if we use pure sql, can't we use one sql to update the primary key? as following:

Update table1 set id=newid where id=oldid

Hello Friend:

I guess you can do it. But, always with caution of the "repeated key". I will do that update operation with HQL.

requests for comments.

You can choose to by-pass the ORM and update the key directly. I would suggest that you use the ORM the way it is designed to be used. In this case, the primary key should be treated as imutable, eg, the setId domain method should be private. Thus you should deleted the old object and create a new one as required.

we should remove and create a new record? OK, that's all right. but what if my record had a million references on many other tables?
should i delete them too or re-reference them again?

Well it all depends. Data cleanup operations would normally be completed using database scripts so that all of the Primary Key changes etc can occur efficiently etc. If this is a part of an application use-case then it is not ideal and does not fit a quality DB design. In this sort of case, use a native query or JDBC and update it directly. Care is required when doing this sort of work.
Your the engineer so your in the best position to choose themost appropriate approach for your system and its limitations/constraints.

allright, but can you possibly tell why why ORM frameworks lack this simple ability? is there a specific reason?
i mean, we could update a PK in Hibernate and then let the DB re-reference all the referenced data by its "UPDATE CASCADE" feature. can't we?
or while we can manage this re-referencing with scripts or DB, why shouldn't we manage that completely with Hibernate?