private String loadConfigFromFile() {
        String result = "";
        if (StringUtils.isBlank(getFileName())) {
            LOG.error("Load metadata: fail to load json {} as the file name is null.", getFileName());
            return result;
        }
        InputStream inStream = null;
        try {
            URL url = getClass().getClassLoader().getResource(getFileName());
            inStream = url != null ? url.openStream() : null;
            if (inStream == null) {
                LOG.error("Load metadata: fail to load json {} as the input stream is null", getFileName());
                return result;
            }
            int size = inStream.available();
            if (size > MAX_ALLOWED_JSON_FILE_SIZE) {
                LOG.error("Load metadata: fail to load json {} as the content size({}) over max allowed size({})",
                        getFileName(), size, MAX_ALLOWED_JSON_FILE_SIZE);
                return result;
            }
            byte[] buffer = new byte[size];
            inStream.read(buffer);
            result = new String(buffer, StandardCharsets.UTF_8);
        } catch (Throwable e) {
            LOG.error("Load metadata: exception thrown while load from file {}", getFileName(), e);
        } finally {
            if (null != inStream) {
                try {
                    inStream.close();
                } catch (IOException e) {
                    LOG.error("Load metadata: fail in inStream.close for file {}", getFileName(), e);
                }
            }
        }
        return result;
    }
load configure from holder

@return the configure info
inlong-dataproxy/dataproxy-source/src/main/java/org/apache/inlong/dataproxy/config/holder/MetaConfigHolder.java