i have two objects, one is parent and one is child, both have "identity" key, and specifies "cascade=save-update" in the parent side of the one-to-many relationship.

I create a parent object A
then create a child object B
specify B as child of A (e.g. A.getBs().add(B);)
specify A as parent of B (e.g. B.setA(A);)

then I persist A

from the hibernate print out, i find that it does a insert of A, which is fine
Then It does an update of B instead of insert of B, which causes an error (as B has not been persisted before)

I try not to use cascade = save-update, and try to persist B before A. However, when persisting B, since the id of A is not generated yet, (it is "identity") the key of A cannot be correctly inserted in the record of B in the database.

Any ideas or suggestions?

Check your unsaved-value mapping

Thx for your remind!

sorry that I read the documentation about unsaved-value, and know it is used to distinguish whether an object is newly instantiated object or transient object. But I still don't have very clear idea on how "any|none|null|id_value" could be used and their differences. I hope I can find some examples or more detailed illustrations on how to properly use them. Can anyone pass me some references or ideas? I found some concepts are very important to me but I cannot make it very clear from the documentation. Many Thank!

Sorry, don't really have time for a more in-depth explanation right now. Take a look at http://www.hibernate.org/hib_docs/reference/html/parent-child.html#parent-child-update