mappedBy

tathagat · **Joined:** Mon Mar 02, 2009 12:01 pm **Posts:** 5

SORRY I POST THIS IN THE WROG FORUM BEFORE
Hi all.
I tried to search this through the forum but couldn't find it.

Is this valid

Code:

Class Father {
@OneToMany (mappedBy="grandFather.Father")
public Child getChild() {
 return child;
}
}

Where Child class has the property Grandfather but not Father (this is just an example).

So basically I want to go 1 step deep.

Thanks in advance!

Cheers

mmerder · **Posted:** Mon Mar 02, 2009 4:03 pm

No, I don't think its possible.

tathagat · **Joined:** Mon Mar 02, 2009 12:01 pm **Posts:** 5

Hey there. Thanks for the quick reply.

Just for anyone who wants to know this. I figured it out.

All I had to do was

Code:

Class Father {
@OneToMany (mappedBy="grandFather")
public Child getChild() {
 return child;
}
} 

Where Father was mapped by Grandfather... Hibernate somehow knew internally that mapping. Pretty neat I would say :).

Cheers

mmerder · **Posted:** Mon Mar 02, 2009 4:12 pm

So your father is the grandfather of his kids? sounds weird...

tathagat · **Joined:** Mon Mar 02, 2009 12:01 pm **Posts:** 5

Told you. It was just an example. Have to admit a bad one!

But I hope the concept is clear - on how to manage this deep hierarchy relationship.

mmerder · **Posted:** Tue Mar 03, 2009 2:49 am

Could you post a clearer example? just out of interest...

tathagat · **Joined:** Mon Mar 02, 2009 12:01 pm **Posts:** 5

I will try. Please let me know if it is still unclear.

Bank offers Deals.
So on Java level, Bank has a List of Deal object.

Now Customer comes. He takes the deal and that creates a Contract.
A Customer can make many contracts.

So Customer->List<Contract>

Also, a Contract is something from a Deal.
So Contract has a foreign key from Deal.

Code:

class Bank{
mappedBy=Bank
private List<Deal> deals;
}

class Customer{
mappedBy=Customer
private List<Contract> contracts;
}

class Contract{
private Customer customer;
private Deal deal;
}

class Deal {
private Bank bank;
}

Hope it is clear till now.

Now on front end, I wanted to see how many contracts the Bank did (irrespective of customers).

So I just create a List of Contract in Bank, which is mappedBy=Deal

Code:

mappedBy=Deal
private List<Contract> contracts;

What did not work was

Code:

mappedBy=Deal.bank
private List<Contract> contracts;

May be I am just making it over complicated..... any suggestions are welcome.

mmerder · **Posted:** Wed Mar 04, 2009 4:01 am

Hmm, never seen that before. Are you sure it works correctly?

I'd probably have used a namedquery in order to count the contracts of a bank.

tathagat · **Joined:** Mon Mar 02, 2009 12:01 pm **Posts:** 5

Hiya.
I don't have enough data in my DB right now to say a definite yes. But it seems to work.

I will post an update by EoW.

Cheers