I am mapping a one to many relationship of 'Product' to 'Stock Item' (a product can have many stock items) using a Set.

<set
name="stockItems"
lazy="true"
inverse="false"
cascade="all-delete-orphan"
sort="unsorted">
<key column="product_id"/>
<one-to-many class="testing.om.StockItem"/>
</set>

All saving/updating/deleting of Stock Items is done via the Product. Each Stock Item has an Integer id property, which I am using in the 'equals' method to determine equality. But I seem to be jumping through so many hoops to make things work smoothly that I'm wondering whether a Set was the right choice. Adding and deleting stock items is fine, but updating is what makes me wonder that I might be using the wrong approach. I have to remove the old StockItem with that ID from the set in Product and then add the new one to effectively update it. There is no way to update an existing member of a set ('add' simply leaves the existing one there, rather than replacing it with the new one, as a Map would if using 'put).

The issue is presumably one of using mutable objects in a set, which can be dangerous. What collection mapping would others use in this context?

TIA

dont use a db identifier in equals/hashcode.

http://www.hibernate.org/109.html

/max

The thrust of the article is that the reason you shouldn't use a db identifier is that it is unavailable to you until the object is saved. Thus is you are adding 'many' objects to a 'one' set, the IDs will be null until the 'one' record is saved (and only the last 'many' object will be stored).

Fair enough, it's a good point, and one whose consequences I had got around hitherto by only ever storing one 'many' object at a time (i.e., saving the parent after each addition of a child to the set). Nonetheless, I have changed this now to using a 'key' property in my equals/hashcode, the 'key' being assigned from a sequence generator. Thus I have a unique key for the child record before the parent is saved, which is no doubt better and gives me more flexibility. It still doesn't get me any further with my original question, though, does it? I am still left with the issue of how to update a specific object in a set. Given the prevalence of sets in the Hibernate examples, I'm surprised not to see this issue discussed more.

if you have cascades on then .saveOrUpdate(p) should be fine.

otherwise get the object and call .saveOrUpdate(si) on each individual stock item...don't understand what you are asking for.