<!DOCTYPE validators PUBLIC "-//OpenSymphony Group//XWork Validator 1.0.2//EN" "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">
<validators>
    <field name="productId">
        <field-validator type="required">
            <message>You must select a product.</message>
        </field-validator>
    </field>
    <field name="quantity">
        <field-validator type="int">
            <param name="min">0</param>
            <message>The quantity cannot be less than zero.</message>
        </field-validator>
    </field>
</validators>