Hi all,

This is my 2nd week using Hibernate and I've been pretty impressed and overwhelm by all the features. Currently, I am trying to map a "derived property" and not sure the right way to go about it. Here's the problem statement:

I have three tables:

table: SHIRT
ID NUMERIC
SIZE VARCHAR
DESCRIPTION VARCHAR

table: APPLE
ID NUMERIC
COLOR VARCHAR

table: SELLABLE_ITEM_TYPE
ID VARCHAR
NAME VARCHAR

The SELLABLE_ITEM_TYPE table contains only two rows, one for SHIRT and one for APPLE, as you may have guessed.

The Shirt bean contains the following properties: id, size, description, and type. The mapping for all the properties is pretty straightforward, except type.

Type is of a SellableItemType object. I'm not quite sure how to tell Hibernate to map this.

A few things I've tried:



but obviously this won't work since SELLABLE_ITEM_TYPE and SHIRT table does not share any property-ref. Is there a way to tell Hibernate that there's no property ref?

Another thing I've tried is using formula and property:



and I'm getting this error:



What's the right way to use formula here? Is it possible to map a formula expression to a complex object?

I read through a few posts but couldn't find similar items discussed. My apology if this is a common question. If so, please send a clue my way so I can narrow my search. Thanks!

Just an update on this one:

I've decided to kill SELLABLE_ITEM_TYPE object and merged its properties to SHIRT and APPLE.

so the mapping becomes simpler:

in SHIRT.hbm.xml:



Still curious though if there's a way in Hibernate to do what I originally set out to do.

The latest thinking was to use formula, get the ID from SELLABLE_ITEM_TYPE and uses a property binder. So, there's a SellableItemTypeEditor with a setAsText(String). I didn't try this so not sure if Hibernate will support it.

I am not sure I understood what you are trying to do, but to me, it looks more like inheritence. If you think in term of classes and not tables, you could probably have a SellableItem interface which is implemented by both Shirt and Apple. Or you cane use a base class "SellableItem" and extend it by both Shirt and Apple. Have a look at "http://www.hibernate.org/hib_docs/reference/en/html/mapping.html#mapping-declaration-subclass" on how to do it.

But ... I'm not really sure that's what you wanna do ...

Hope it helps !

Guillaume

It is related to inheritance but I don't think it's related to this specific question.

To simplify, the question is whether it's possible to have a one-to-many relationship when you don't have a connecting primary/foreign key. So, in terms of object model, your object A wants to have a reference to object B but in the data model, there's nothing that indicates that's the case. Obviously we're dealing with two legacy data models here :) Also, this is read only, no expectation to insert/update/delete on the Association.

Another solution is to add a link table between the two if you're allowed.