writeJsonResponse(HttpServletResponse.SC_BAD_REQUEST, escapeJsonKeyValue(MESSAGE_FIELD, "Referer is invalid."));
            return;
        }

        if (!fessConfig.isApiSearchScroll()) {
            writeJsonResponse(HttpServletResponse.SC_BAD_REQUEST, escapeJsonKeyValue(MESSAGE_FIELD, "Scroll Search is not available."));
            return;
        }

     * The value is, e.g. false <br>
     * @return The determination, true or false. (if not found, exception but basically no way)
     */
    boolean isApiSearchScroll();

    /**
     * Get the value for the key 'api.json.response.headers'. <br>
     * The value is, e.g.  <br>
     * @return The value of found property. (NotNull: if not found, exception but basically no way)