Struts iterator tag , property and textfield tags inside iterator. Problem passing list object

Question

I have a object exampleDTO.

ExampleDTO
{
private Map<Integer, LineNumberDTO> lineList;
private String  rept;
}

LineNumberDTO
{
line_number;
col1_descriptor;
col1_value;
col2_value;
}

I have this jsp where I am iterating throught this lineList.My jsp looks like this

<s:form action="AddBatchEntry" method="post">

<div class="content-box">
    <table id="batchHeaderFields">
        <tbody>
            <tr>
            <td><s:property value="batchNumber"/></td><td><s:textfield name="exampleDTO.batchNumber" readonly="true" style="bgcolor:blue"/></td>
            <td><s:property value="batchName"/></td><td><s:textfield name="exampleDTO.batchName" size="10" readonly="true"/></td>
            </tr>
            <tr><td><s:property value="ReportNumber"/></td><td><s:textfield name="exampleDTO.Rept"/></td>           
        </tbody>
    </table>
    <table id="tlines" >
        <tbody>     
                <thead>
                <tr>
                    <th>LINE NUMBER</th>
                    <th>LINE DESCRIPTOR</th>
                    <th>value1</th>
                    <th>value2</th>
                    
                </tr>
                </thead>
                <s:iterator value="%{exampleDTO.lineList}">
                <tr>
                
                    <td><s:property value="%{value.line_number}"/></td>
                    <td><s:property value="%{value.col1_descriptor}" /></td>
                    <td><s:textfield name="%{value.col1_value}" size="4"/></td>
                    <td><s:textfield name="%{value.col2_value}" size="4"/></td>
                    
                </tr>
                
                </s:iterator>
        </tbody>
    </table>

    </div>
    </div>
</div>
<div class="title-button">
        <s:submit value="%{getText('button.AddNextEntry')}" />
</div>
</s:form>

listList is populated depending on batch number.I am able to display line_number and col1_descriptor in this page. I am taking 2 inputs col1_value and col1_value. when i enter these values and submit. I am getting 'lineList' as null in my action class. But i am getting all other values including 'rept' which i am inputting in this page .

How do I get lineList object in my action class.