code: private static InputStream getResourceAsStream(String path) throws IOException {
      if (StringUtils.isEmpty(path)) {
        return null;
      }
  
      // first try to load as file
      File file = new File(path);
      if (file.exists() && file.isFile()) {
        return new FileInputStream(file);
      }
  
      // if not a file fallback to classloader resource
      return CertificateLoader.class.getResourceAsStream(path);
    }
docs: Tries to load the given resource as file, or if no file exists as classpath resource.
  @param path Filesystem or classpath path
  @return InputStream or null if neither file nor classpath resource is found
  @throws IOException