I'm trying to map a one-to-many relationship and get an insert or update of the parent object to cause a Set of child objects to be inserted into the database with their foreign keys set automatically to the parent key, etc.

The issue is that the implementation of the Set.add method wants a unique object but the objects aren't unique until they get an ID from the database. So I'm forced to save each child object individually and then add them to the parent object. I'd really like hibernate to do all the work and insert them automagically when I update the parent object:)

Is it as simple as overriding the equals method of the child object so they appear to be unique even if their ID's are null? Or is hibernate depending on the equals method in some way so that I can't change it?

Thanks,
Rich

Remember that you can't change the hashcode of an object while it is in a set. So no, no-one has ever had a good solution for this.

I generally advise not to make equals to an id comparison. It should compare "business keys", not surrogate keys.

(Alternatively, use a <bag>.)

"you can't change the hashcode of an object while it is in a set"? Do you mean at runtime? i.e.: You can't add objects to a set and then do something that will change the hashcodes of the objects while the set is in scope?

BTW - I used middlegen and hbmtojava to generate my hibernate code. It uses the primary key fields in the equals and hashcode methods by default. It sounds like I can change them if I need to.

Thanks -