Get value from checkbox inside iterator, in struts2

I have a checkbox inside an iterator, in a jsp page. Whatever I tried, the attribute value of the checkbox tag stay with the 'true' value, even when the value of the fieldvalue is the one I want. But I can't get back it. I only get 'true'.

 <s:iterator
                    id="pieceJointe"
                    value="listePiecesJointesTrouvees">
                    <tr height="30">
                        <td>
                            <s:property value="codeDemande" />
                        </td>
                        <td
                            headers="actions"
                            class="center">         
                            <s:checkbox 
                            value="%{chemin}"
                            fieldvalue="%{chemin}"                      
                            name="checkbox" /> 
                        </td>           
                    </tr>
                </s:iterator>

The variable 'chemin' getting back with fieldset attribut is the one I want. I can see it with the Web Inspector but I can't take it in the code. I only get back the value of 'value' variable wich is desesperatly "true" value.

If you have an idea,

Thanks for your help and sorry for my bad english,

Stephane