Composite Keys or Multiple Complex Parameters Properties

You might have noticed that in the above examples there is only a single key being used as specified in the resultMap by the column attribute. This would suggest that only a single column can be associated to a related mapped statement. However, there is an alternate syntax that allows multiple columns to be passed to the related mapped statement. This comes in handy for situations where a composite key relationship exists, or even if you simply want to use a parameter of some name other than #value#. The alternate syntax for the column attribute is simply param1=column1, param2=column2, ... , paramN=columnN. Consider the example below where the PAYMENT table is keyed by both Customer ID and Order ID:

<resultMap id="select-order-result" class="order">
    <result property="id" column="ORD_ID"/>
    <result property="customerId" column="ORD_CST_ID"/>
    ...
    <result property="payments" column="{itemId=ORD_ID, custId=ORD_CST_ID}"
      select="selectOrderPayments"/>
</resultMap>

<statement id="selectOrderPayments" resultMap="select-payment-result">
    select * from PAYMENT
    where PAY_ORD_ID = #itemId#
    and PAY_CST_ID = #custId#
</statement>

Optionally you can just specify the column names as long as they're in the same order as the parameters. For example:

{ORD_ID, ORD_CST_ID}