I might be having a moment, but here goes.
I have a Coupon class that contains an integer list of BrandIds that
specifies which brands of product the coupon is good for. We don't want
the whole Brand object because it contains a lot of information that's
not necessary for the coupon's CalculateDiscount() method to function,
so we'd just like a list of integers returned from iBATIS. int[],
List<int>, just a list of integers of some sort.
The relevant parts of the database tables look like this:
Coupons:
CouponId (PK)
Code
Coupons_Brands: (M:N relationship table)
CouponId (FK)
BrandId (FK)
To avoid the N+1 selects, we tried a SQL statement like the following:
SELECT
cou.CouponId AS CouponId,
cou.Code AS CouponCode,
cou_b.BrandId AS CouponBrandId,
FROM SkiviezInv.Coupons AS cou
LEFT OUTER JOIN Coupons_Brands AS cou_b
ON cou.CouponId = cou_b.CouponId
But then we got stuck at defining the <resultMap>. Just using the
property and column attributes doesn't work ("no type handler for List`1
is registered"). The furthest we got was defining another result map for
the integer type, like this:
<resultMap id="ResultMapCoupon" class="Coupon" groupBy="Id">
<result column="CouponId" property="Id" />
<result
property="BrandIds"
resultMapping="Coupon.ResultMapCouponBrandId" />
</resultMap>
<resultMap id="ResultMapCouponBrandId" class="int">
<result property="value" column="CouponBrandId" />
</resultMap>
This set up would indeed create a List<int> with the proper Count (e.g.,
two BrandIds), but they're always all set to 0. It seems like this would
be supported (see example 3.41 in the DataMapper documentation), but it
just doesn't seem to work.
We've worked around it by just using the select attribute and getting
rid of the join.
This is on DataMapper 1.6.1.
Thanks for any insight!
V/R,
Nicholas Piasecki
