Hi Marina,
Marina Vatkina wrote:
Hi Greg,
If this is the case, why would you need to remove items by a specific
offering?
Good question. A shopping cart can have more than one item containing
a particular offering. I do this so that I can support behavior like,
"Buy two cats at the regular price, get a third cat at half price." To
support this, (in a business class) I create 2 items. The first item
has 'cat' as the offering, and the quantity set to 2. The second item
has 'cat' as the offering, quantity 1, and a reference to a Discount
object with a 'percent off' value of .50f. The discount gets applied
only to the second item.
I am anticipating that it will be common for a user to remove all of
the items that contain a particular offering (decided we don't need any
cats today). So, I created a convenience method to handle this. I
also have methods for removing a particular item, and for updating the
quantity of an item.
Does this make sense?
Thanks.
Greg
Greg Ederer
wrote:
Hi Marina,
In my model, instances of Offering represent things that a Vendor
offers for sale. Product and Service directly subclass Offering and
are, themselves, subclassed by classes representing more specialized
kinds of products and services (e.g., Subscription, Garment, et
cetera).
A ShoppingCartItem has an Offering (as well as a quantity, a unit
price, a collection of Discounts, et cetera).
I suppose that I could establish a many-to-many relationship between
Offering and ShoppingCartItem. Does that strike you as being a good
idea?
Would it be a many-to-one if item can have only one offering?
The solution most probably depends on the use case. If you don't the
remove
quite often, the bulk delete might be a better solution (as long as it
doesn't
intervene with the in-memory transaction processing as it happens
directly
in the database, and won't affect the cache).
regards,
-marina
Cheers,
Greg
Marina Vatkina wrote:
Hi Greg,
Does it mean that there is no relationship from Offering to Item?
Is it worth adding (and maintaining so that they are always at sync)?
thanks,
-marina
Greg Ederer wrote:
Hi,
I have a method that removes a persistent object from a collection
based on a property of the object being removed, like so:
/**
* Removes all ShoppingCartItems containing this
* offering
*/
public void removeItem(Offering offering)
{
List<ShoppingCartItem> iList = new
ArrayList<ShoppingCartItem>(getItems());
for(ShoppingCartItem i : iList)
{
if(i.getOffering().equals(offering))
{
getItems().remove(i);
}
}
}
Is this the best way to do this?
Cheers,
Greg
p.s.: I'm so glad I found this list. I feel like I've been groping in
the dark with JPA. Thanks for all the help! --G
--
| E R G O N O S I S
| Greg Ederer
| Lead Developer
| greg@ergonosis.com
| 360.379.1157
| | OpenDocument - OK <http://openoffice.org/>
|
--
| E R G O N O S I S
| Greg Ederer
| Lead Developer
| greg@ergonosis.com
| 360.379.1157
| | OpenDocument - OK <http://openoffice.org/>
|