Im just learning Hibernate so this should be a good opportunity to earn some credits :)

My problem is as follows. I am trying to create mapping files for a hierarchical relationship. The basic idea is this. I have (0-N) accounts. Each account has (0-N) computers. Each computer has (0-N) connections. Pretty simple huh? Here's the catch.

I want the accounts table to have a generated primary key. No problem.

I want the computers table to have a generated (primary?) key which is unique to each account (FK?) but not to the table as a whole. An example table might be as follows:


And so on....

Likewise, I would like to have the connections table have a generated (primary?) key which is unique to the (account,machine) pair but not to the table as a whole. For example:



My question is, how do I set up the mapping files to handle this situation? I have searched through the forum, the online docs, and "Hibernate, A J2EE Developer's Guide" to no avail.

Clarification would be greatly appreciated. Also, feel free to make suggestions about my database schema if you think there is a better way to do it.

I don’t think the scenario you described can be solved directly be just configuration in the maps. If I understand you right you are using composite keys as your identifier. (Primary key composed of several columns in the table)

http://www.hibernate.org/hib_docs/v3/reference/en/html/mapping.html#mapping-declaration-compositeid

When using composite key, Hibernate can not auto-generate the value for the identifier, which must then be handled in the application.

The problem you are describing is not possible to configure up just out of the box in the maps

The primary key section in the Account Map could look something like:


The primary key section in the Computer Map could look something like:


Hope this helps!

Do you really need that connection's id and computer's id can be shared? Otherwise, you only have to map two one-to-many relations and forget about composite keys... You will be able to traverse the object hierarchy either way.

Bye.

No. I guess my thinking was that I dont want someone (in the application) to be able to reference the machine without also knowing its account number, for security reasons. I guess I could, in theory, handle that at the application level as opposed to the database level... I just figured it would be more efficient to do it at the database level, thats all. Of course, in the real thing I wouldn't be using incremental keys. That was done for illustration purposes only.