How to send a Javascript variable to server side?

I must add items to an existing code, but I do not know all the patterns established. I need to retrieve a value from a numeric field in javascript, store it in a JSP tag variable and submit it to a Java method. I know javascript is client side and the server-side Java.

This is a numeric field "ZONE" whose value must be recovered for a loop

The added code is input "ZONE", the Action buton "ADD_ELEMENT_LISTE_OUVERTE_1" and the variable and loop "zone".

thanks !

JSP-side code:

<popo:form>



    <div class="left">

    nombre de colonnes <input type="number" id="zone"  name="zone" class="text" maxlength="25" valeur="" />

    </div>

    <div class="right">

        <%controller.getContext().getInteger(ListeOuverteContributionDetailController.ZONE) =%>



        <script type="text/javascript">

            function getZoneJS() {

                var zone=(parseInt(document.form.elements["zone"].value));

                if (zone != null ){

                    return zone;

                }                                        

            }

        </script>



        <popo:action name="ADD_ELEMENT_LISTE_OUVERTE_1" text="Ajouter les colonnes" />                                

    </div>



    <popo:listpanel dtcid="<%=ListeOuverteContributionDetailController.DTC_ELEMENTS_LISTE_OUVERTE%>" readonly="false">



        <popo:grid cols="2" colwidth="200px,*">

            <popo:iterator>

                <popo:field name="VALEUR"/>

                <popo:action name="DELETE_ELEMENT_LISTE_OUVERTE" text="<%=controller.getTextSupprimer()%>" style="icon"/>

            </popo:iterator>

        </popo:grid>

    </popo:listpanel>



    <div class="left">

        <popo:action name="ADD_ELEMENT_LISTE_OUVERTE" text="Ajouter un élément"/>   

    </div>

    <div class="left">

        <%--<popo:link address="<%=AddressItems.IMPORT_LISTE_OUVERTE_ADDRESS.getAddress()%>" fields="CHAMP_ID" objects="<%="FOR_ID," + controller.getChampKey(champId)+","+controller.DTC_ELEMENTS_LISTE_OUVERTE%>" style="button">Importer</popo:link>--%>

        <popo:action name="IMPORT_LISTE_OUVERTE" text="Importer"/>

    </div>

    <div class="left">

        <popo:action name="EXPORT_LISTE_OUVERTE" text="Exporter" /> 

    </div>

    <div class="clear"></div>



    <div class="buttonbar">

        <div class="left">

            <popo:link address="<%=AddressItems.SECTION_CONTRIBUTION_DETAIL_ADDRESS.getAddress()%>" fields="SEC_ID" objects="FOR_ID" params="<%="MODE=" + DetailController.MODE_EDIT%>" style="button" confirm="<%=Constantes.MSG_CONFIRM_QUITTER_ECRAN_CREATION_MAJ%>">Abandonner</popo:link>

        </div>

        <div class="right">

            <popo:action name="SAVE_MODIFICATIONS_LISTE_OUVERTE" text="Enregistrer" isdefaultaction="true"/>

        </div>

    </div>

</popo:form>

Java method that will retrieve the ZONE variable to loop

public class ListeOuverteContributionDetailController extends AbstractContributionController {



    /**

     * Liste des éléments de la liste ouverte.

     */

    public static final String DTC_ELEMENTS_LISTE_OUVERTE = "DTC_ELEMENTS_LISTE_OUVERTE";

    public static final String SI_AJOUT_ELEMENT = "SI_AJOUT_ELEMENT";

    public static final String ZONE = "ZONE";



    public Message executeAddElementListeOuverte1() throws KUserException, KSystemException {



        final DtCollection<ElementListeOuverte> elementsListeOuverte = getContext().<ElementListeOuverte>getDtCollectionInput(DTC_ELEMENTS_LISTE_OUVERTE).validate();

        // la valeur zone qui doit être récupérée de la JSP

        final int zone = Integer.parseInt(getContext().getString(ZONE));

        for (int i = 1; i <= zone; i++) {

            // On ajoute un élément à la liste des éléments stockée dans le contexte en le flagant "Nouveau"

            final ElementListeOuverte elementListeOuverte = new ElementListeOuverte();

            final ChampContribution champ = getContext().<ChampContribution>getDtObjectInput(getChampKey(getContext().getLong(CHAMP_ID))).validate();

            elementListeOuverte.setChampId(champ.getChampId());

            elementListeOuverte.setSiNouveau(true);

            elementListeOuverte.setSiSupprime(false);

            elementsListeOuverte.add(elementListeOuverte);



            getContext().put(SI_AJOUT_ELEMENT, true);

        }

        return refresh();

    }

}