private Service Service;
    private Vehicule v;
    private Map<String, Object> map= new HashMap<>();

    public String query()
    {

            Service = new ServiceImpl();
            v = new Vehicule();
            v= Service.getVehiculeByImmat(field1);
            map.put("date", v.getdate().toString());
    map.put("kilometrage", v.getKilometrage());


    return "success";

    }

$(document).ready(function(){

      $('#field1').change(function(){


          var selectedValue = $('#field1').val();
            if ($.trim(selectedValue).length > 0)
             {
          alert(selectedValue);
                $.ajax(
                {
                    type: 'POST',
                    url  : "<s:url action='query'/>",
                    dataType : 'json',
                    data: { field1: selectedValue},
                    success: function(result){

                        $.each(result, function(key,value)
                        {                      $("#"+key).val(value);
                                    } );

                },

                 });

            }

        }
      );


    });

<action name="query" class="action.GestionVehicules" method="query">
          <result name="success" type="json">map</result>
    </action>

ActionContext.getContext().setLocale(Locale.US);