private JSONObject saveModelNodes(List<Model> nodesToSave) throws JSONException {
    JSONArray errorNodes = new JSONArray();

    JSONObject respObj = new JSONObject();

    // loop over nodes and order them ascending
    TreeMap<Integer, Model> treeMap = new TreeMap<Integer, Model>();
    for (int i = 0; i < nodesToSave.size(); i++) {

      Model model = (Model) nodesToSave.get(i);
      // loads all nodes guiid with type error

      respObj.put(model.getGuiId(), "OK");
      respObj.put("label", model.getLabel());

      if (model.getParentId() != null) {
        // look up for its id: if null --> newly created node
        Integer id = model.getId();
        if (id == null) {
          treeMap.put(Integer.valueOf("-" + i + 1), model);
        } else {
          // else to modify node
          treeMap.put(model.getId(), model);
        }

      } else {
        // root node --> save first
        try {
          if (model.getId() != null) {
            modelDao.modifyModel(model);
            respObj.put(model.getGuiId(), model.getId());
            respObj.put(model.getId() + "", model.getLabel());
          } else {
            Integer index = modelDao.insertModel(model);
            respObj.put(model.getGuiId(), index);
            respObj.put(index + "", model.getLabel());
          }
        } catch (Exception e) {
          // send error!!!
          respObj.put(model.getGuiId(), "KO");
        }
      }
    }

    Set set = treeMap.entrySet();
    // Get an iterator
    Iterator it = set.iterator();
    // loop again over treemap
    while (it.hasNext()) {
      Map.Entry orderedEntry = (Map.Entry) it.next();
      // check that parent exists
      Model orderedNode = (Model) orderedEntry.getValue();

      // GET JSON OBJECT VALUE
      Integer parentId = orderedNode.getParentId();
      try {
        Model parent = modelDao.loadModelWithoutChildrenById(parentId);
        if (parent != null) {
          // if parent exists--> save
          // if node id is negative --> insert
          if (orderedNode.getId() == null) {
            Integer newId = modelDao.insertModel(orderedNode);
            if (newId != null) {
              orderedNode.setId(newId);
              respObj.put(orderedNode.getGuiId(), newId);
              respObj.put(newId + "", orderedNode.getLabel());
            } else {
              respObj.put(orderedNode.getGuiId(), "KO");
            }
          } else {
            // else update
            modelDao.modifyModel(orderedNode);
            respObj.put(orderedNode.getGuiId(), orderedNode.getId());
            respObj.put(orderedNode.getId() + "", orderedNode.getLabel());
          }
        }
      } catch (Exception e) {
        // if parentId != null but no parent node stored on db --> exception
        respObj.put(orderedNode.getGuiId(), "KO");
      }
    }
    return respObj;
  }
  private List<Model> deserializeNodesJSONArray(JSONArray rows) throws JSONException {
    List<Model> toReturn = new ArrayList<Model>();
    HashMap<String, Model> labels = new HashMap<String, Model>();
    for (int i = 0; i < rows.length(); i++) {

      JSONObject obj = (JSONObject) rows.get(i);

      Model model = new Model();
      // always present guiId
      String guiId = obj.getString("id");
      model.setGuiId(guiId);

      try {
        model.setId(obj.getInt("modelId"));
      } catch (Throwable t) {
        // nothing
        model.setId(null);
      }

      try {
        model.setParentId(obj.getInt("parentId"));
      } catch (Throwable t) {
        // nothing
        model.setParentId(null);
      }
      try {
        model.setCode(obj.getString("code"));
        try {
          model.setDescription(obj.getString("description"));
        } catch (Throwable t) {
          // nothing
          model.setDescription(null);
        }

        String labelKey;
        try {
          labelKey = obj.getString("label");
        } catch (Throwable t) {
          labelKey = java.util.UUID.randomUUID().toString();
        }
        model.setLabel(labelKey);
        if (!labels.containsKey(labelKey)) {
          labels.put(labelKey, model);
        } else {
          // skip it
          continue;
        }
        model.setName(obj.getString("name"));
        model.setTypeCd(obj.getString("type"));
        model.setTypeId(obj.getInt("typeId"));
        try {
          model.setTypeDescription(obj.getString("typeDescr"));
        } catch (Throwable t) {
          // nothing
          model.setTypeDescription(null);
        }
        try {
          model.setKpiId(obj.getInt("kpiId"));
        } catch (Throwable t) {
          // nothing
          model.setKpiId(null);
        }
        // add the udpValues to Model Instance Definition, that will be serialized
        List<UdpValue> udpValues = new ArrayList<UdpValue>();
        JSONArray jsonArray = null;
        try {
          jsonArray = obj.getJSONArray("udpValues");
        } catch (Throwable t) {
          jsonArray = new JSONArray();
        }
        logger.debug("found udpValues Array containing number of Udp " + jsonArray.length());
        for (int j = 0; j < jsonArray.length(); j++) {
          JSONObject objJS = (JSONObject) jsonArray.get(j);
          // only label and value information are retrieved by JSON object
          String labelJ = objJS.getString("name");
          String value = objJS.getString("value");

          UdpValue udpValue = new UdpValue();

          // reference id is the kpi id
          udpValue.setLabel(obj.getString("label"));
          udpValue.setValue(value);
          udpValue.setReferenceId(model.getId());

          // get the UDP to get ID (otherwise could be taken in js page)
          Udp udp = DAOFactory.getUdpDAO().loadByLabelAndFamily(labelJ, "MODEL");
          Domain familyDomain = DAOFactory.getDomainDAO().loadDomainById(udp.getFamilyId());
          logger.debug(
              "Udp value assigning value "
                  + value
                  + " to UDP with label "
                  + udp.getLabel()
                  + " and Model Instance with label "
                  + model.getLabel());
          udpValue.setLabel(udp.getLabel());
          udpValue.setName(udp.getName());
          udpValue.setFamily(familyDomain != null ? familyDomain.getValueCd() : null);
          udpValue.setUdpId(udp.getUdpId());

          udpValues.add(udpValue);
        }
        model.setUdpValues(udpValues);

        String value = obj.getString("toSave");
      } catch (Throwable t) {
        logger.debug("Deserialization error on node: " + guiId);
      }
      toReturn.add(model);
    }
    return toReturn;
  }