code: public void serveFile(final String contentFile, final String root, final String validSubPaths) {
      if (rootPath == null) {
        final String slash = root.endsWith("/") ? "" : "/";
        rootPath = root + slash;
      }
  
      final String contentPath = rootPath + context.request.uri;
  
      try {
        final byte[] fileContent = readFile(contentPath);
        completes().with(Response.of(Ok, Body.from(fileContent, Body.Encoding.UTF8).content));
      } catch (IOException e) {
        completes().with(Response.of(InternalServerError));
      } catch (IllegalArgumentException e) {
        completes().with(Response.of(NotFound));
      }
    }
docs: Completes with {@code Ok} and the file content or {@code NotFound}.
  @param contentFile the String name of the content file to be served
  @param root the String root path of the static content
  @param validSubPaths the String indicating the valid file paths under the root