public void setParameter(String paramName, String param){
        String[] prms = requestParameters.get(paramName);
        if (prms != null) {
            List<String> list = new ArrayList<>(Arrays.asList(prms));
            list.add(param);
            requestParameters.replace(paramName, (String[]) list.toArray());
        } else {
            prms = new String[]{param};
            requestParameters.put(paramName, prms);
        }
    }