try (CloseableHttpResponse response = httpClient.execute(httpPost)) {
            if (response.getStatusLine().getStatusCode() != Constants.OK_STATUS_CODE) {
                logger.error("Failed to access {}, code: {}.", url, response.getStatusLine().getStatusCode());
                return null;
            }

            data.setContent(EntityUtils.toString(response.getEntity(), Charsets.UTF_8));

                httpRequest = new HttpGet(buf.toString());
            }

            executor.accept(httpRequest, (response, entity) -> {
                final int httpStatusCode = response.getStatusLine().getStatusCode();
                if (httpStatusCode < 400 || httpStatusCode == 401) {
                    parseTokenPage(tokenPattern, responseParams, entity);
                } else {
                    String content;

            });
        } catch (final WebApiException e) {
            logger.debug("Failed to access to Web API.", e);
            response.sendError(e.getStatusCode(), e.getMessage());
        }
    }

    protected void processRequest(final HttpServletRequest request, final HttpServletResponse response, final String path) {

        throw new HttpErrorStatusCodeException(response.getMethod(), effectiveUri.toString(), response.getStatusLine().getStatusCode(), response.getStatusLine().getReasonPhrase());
    }

    private synchronized CloseableHttpClient getClient() {
        if (client == null) {
            HttpClientBuilder builder = HttpClientBuilder.create();

            // get a content
            final HttpResponse response = executeHttpClient(httpGet);
            httpEntity = response.getEntity();

            final int httpStatusCode = response.getStatusLine().getStatusCode();
            if (httpStatusCode == 200) {

                // check file size
                final Header contentLengthHeader = response.getFirstHeader("Content-Length");