CDATA validation for lists in jsp

I have a list of fields in my jsp

<s:iterator value="someList" status="counter" var="item">
        <div class="col-xs-7">
            <div class="col-xs-3"><s:textfield name="fromValue" id="fromValue_%{#counter.index}" value="%{#item.fromValue}" cssClass="abc form-control" /></div>
            <div class="col-xs-3"><s:textfield name="toValue" id="toValue%{#counter.index}" value="%{#item.toValue}" cssClass="abc form-control"/></div>        
            <div class="col-xs-3"><s:textfield name="value1" id="rateValue1_%{#counter.index}" value="%{#item.value}" cssClass="abc form-control"/></div>       
            <div class="col-xs-3"><a href="#" class="dynaRowRemove2 col-xs-3" style="text-decoration: none;font-weight:bold;"><s:text name="remove"/></a></div>
        </div>
</s:iterator>

I need to validate against each value for value1 how do i do that ?

I understand this is how it is done for any single fields

<validator type="fieldexpression">
<param name="fieldName">value1</param>
<param name="expression"><![CDATA[some regular expression]]></param>
<message key="invalid" /> 
</validator>

Not sure how to do it for iterators..