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Hibernate : Bidirectional Association

Sandeep Vaid
Ranch Hand

Joined: Feb 27, 2006
Posts: 390
Assume one to many relationship exists between Item and Bid and is bidirectional. As we need to access them in either way,to save an item, we need to write :

bid.setItem(item);//Line 1
Set bidset = new HashSet();
bidset.add(bid);
item.setBids(bidset);// Line 2

CASE 1:
suppose i only comment line 1 and then save item :
a)it's inserting into ITEM table
b) It's inserting into BID table but the FK (ITEM_ID) is setting as null...

So this means i won;t be able to retrieve bids from this item.. ?


CASE 2:
suppose i only comment line 2 and then save bid :
a) insert into bid
b) insert into item
c) update bid to set FK (ITEM_ID) properly

Moreover i don't understand that why in case 2) it executed the update (c)
while in case 1) it doesn't ?
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Hibernate : Bidirectional Association