}
                    return null;
                }).filter(o -> o != null && keySet.add(o.getFirst())).collect(Collectors.toList()));
            }
            propMap.put(DEFAULT_SORT_VALUES, list);
        }
        return list.stream().map(p -> {
            final String key = p.getFirst();
            if (StringUtil.isEmpty(key) || userBean

        }
    }

    @Override
    protected void writeHeaders(final HttpServletResponse response) {
        ComponentUtil.getFessConfig().getApiJsonResponseHeaderList().forEach(e -> response.setHeader(e.getFirst(), e.getSecond()));
    }

    protected void writeJsonResponse(final int status, final Throwable t) {
        final Supplier<String> stacktraceString = () -> {