I studied the hibernate annotations refernece guide and I really wonder if there is a way to annotate a class in such way that a unique key constraint for some fields are generated ? Any hints on this ? Did I miss something?

@Column(unique=true)

And what if I need a unique key that spans multiple rows ?

Did you try searching the documentation for "unique"? It's the first hit, actually.

do you mean the hibernate annotaions docs ? the search pointed me to an example that doesnt tell me anything. I know how to build a unique identifier. But thats not my concern. I have a surrogate key and need to build a unique constraint on some other cols. Excuse me if I#m too blind I don't see it in the docs.
Thomas

Go there:

http://www.hibernate.org/hib_docs/annot ... ml_single/

Hit CTRL+F, type "unique", hit ENTER.

"You can also define unique constraints to the table using the @UniqueConstraint annotation in conjunction with @Table (for a unique constraint bound to a single column, refer to @Column)."

i knew it must be there. Thanks for your advice.
Thomas