Struts 2's inbuit Validations on List items

Question

<s:iterator value="listOfValues" status="row">
    <s:textfield name="listOfVoObjects[${row.index}].itemId"/>
    <s:textfield name="listOfVoObjects[${row.index}].itemName"/>
</s:iterator>

In this scenario, does anybody know how to do validations on each itemId and itemName in the listOfValues when the form is submitted using the XML validations in Struits2 ??

Thanks in Advance, `A