I've read that the Primary Key field can be a wrapper class. But, no where has it been mentioned if it can be any Java API class. To be specific, can java.util.Vector be a Primary Key class for my bean?

Robert Castaneda

I am not aware of any application Server that would allow a Vector to be specified as a primary key type for an Entity Bean.

Logically when you think about it, there is no clear database type[s] that you would map it to in a relational database.

If you are trying to make a compound Primary Key, then you should use a wrapper class that contains simple types.