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;

                message = "[" + errorCode + "] Failed to access to Web API.";
                logger.warn(message, e);
            }
            response.sendError(e.getStatusCode(), message);
        }
    }

    /**
     * Processes API requests to the search engine.
     * Handles both regular API calls and plugin requests.
     *