Hi all,

I'm hopeful that this can be done in Hibernate, i'm just not sure how it would be mapped.

I have two tables PRODUCT and ORDER_LINE

PRODUCT
-------
product_id (pk)
product_name


ORDER_LINE
----------
order_line_id (pk)
product_id (fk)
product_name
qty

Naturally i have two classes Product and OrderLine and OrderLine has a Many-To-One relationship with Product.

What i want is that when i save OrderLine i also want the productName property of the Product object to be written into the product_name column of the ORDER_LINE table.

No idea how to map this though in hibernate. Any ideas from anyone?

Thanks in advance.

Hmmm, there's probably a business reason why you want redundant product_name data in both tables. Since you have a fk relationship to Product, then you have product_name from the Product table.

But, to answer your question:
Two scenarios - insert and update

If you are inserting/creating an OrderLine and assigning an existing Product then assign OrderLine.productName like this (pseudo-code):



If you are updating an existing OrderLine then you can use your hierarchy and reach into product like this:





I don't think you can map something like this because product_name is not part of the relational hierarchy. <overkill>You could probably use a db trigger to do it </overkill>

Yeah jruffin,

I know there are workarounds like having a productName property in the OrderLine class or using a db trigger.

I was really hoping for a way to map this though...

It could be done the following way: -



The idea is to map the product_name as a normal property and then add the code in get/set of Product and productName to keep it in sync. You would not have to call get/set of productName explicitly. When Hibernate calls the get/set of productName, its value would be fetched from product.

In the setProduct method you could set the productName also, but I don't think it is required.

Thanks jayesh but that's not really a mapping solution. I don't want to a productName property in my OrderLine class... to be honest i'd rather use a db trigger as i like to keep my code clean and following OO principles.

So is everyone pretty much saying that it CAN'T be done using a pure hibernate mapping solution?

Your original post is a little ambiguous... In it you have productName under table OrderLine... in later posts you mention you don't want productName in OrderLine. I may not be following you correctly.

If you don't want productName in OrderLine and you already have productName in Product - I don't understand what's left...

What's the question at hand?

Oh, you want to store in table OrderLine.productName the value from table Product.productName but not have java object OrderLine contain a productName attribute and/or accessors? And you'd like this controlled by a mapping file?

Not.

You could try and use <join>.