try {
            final ActionResponse actionResponse = ssoManager.getResponse(SsoResponseType.METADATA);
            if (actionResponse == null) {
                throw responseManager.new400("Unsupported request type.");
            }
            return actionResponse;
        } catch (final SsoMessageException e) {
            if (e.getCause() == null) {
                if (logger.isDebugEnabled()) {

            // 404
            throw responseManager.new404("Thumbnail for " + form.docId + " is not found.");
        }

        final File thumbnailFile = thumbnailManager.getThumbnailFile(doc);
        if (thumbnailFile == null) {
            if (fessConfig.isThumbnailEnabled()) {
                thumbnailManager.offer(doc);
            }
            // 404

     *
     * @return the stream response
     */
    public StreamResponse asStream() {
        if (osddFile == null) {
            throw ComponentUtil.getResponseManager().new404("Unsupported Open Search Description Document response.");
        }

        return new StreamResponse(osddFile.getName()).contentType(contentType + "; charset=" + encoding).stream(out -> {