/**
   * Parses AGGREGATE method parameters for WPS execute xml variables
   *
   * @param lc WFS layer configuration
   * @param json Method parameters and layer info from the front
   * @param baseUrl Url for Geoserver WPS reference input (input
   * @param aggre_field Field name for aggregate function
   * @return AggregateMethodParams parameters for WPS execution
   *     **********************************************************************
   */
  private AggregateMethodParams parseAggregateParams(
      WFSLayerConfiguration lc,
      JSONObject json,
      String baseUrl,
      String aggre_field,
      List<String> aggre_funcs)
      throws ServiceException {
    AggregateMethodParams method = new AggregateMethodParams();
    //
    method.setMethod(AGGREGATE);
    try {
      method.setLayer_id(ConversionHelper.getInt(lc.getLayerId(), 0));
      method.setServiceUrl(lc.getURL());
      baseUrl = baseUrl.replace("&", "&amp;");
      method.setHref(baseUrl + String.valueOf(lc.getLayerId()));
      method.setTypeName(lc.getFeatureNamespace() + ":" + lc.getFeatureElement());
      method.setMaxFeatures(String.valueOf(lc.getMaxFeatures()));
      method.setSrsName(lc.getSRSName());
      method.setOutputFormat(DEFAULT_OUTPUT_FORMAT);
      method.setVersion(lc.getWFSVersion());
      method.setXmlns(
          "xmlns:" + lc.getFeatureNamespace() + "=\"" + lc.getFeatureNamespaceURI() + "\"");

      method.setGeom(lc.getGMLGeometryProperty());

      JSONObject bbox = null;

      bbox = json.getJSONObject("bbox");
      method.setX_lower(bbox.optString("left"));
      method.setY_lower(bbox.optString("bottom"));
      method.setX_upper(bbox.optString("right"));
      method.setY_upper(bbox.optString("top"));

      // TODO: loop fields - current solution only for 1st field
      method.setAggreField1(aggre_field);
      method.setAggreFunctions(aggre_funcs);

    } catch (JSONException e) {
      throw new ServiceException("Method parameters missing.");
    }

    return method;
  }