public static void showImage(Long id) {
   Content content = Content.findById(id);
   notFoundIfNull(content);
   response.setContentTypeIfNotSet(content.image.type());
   File file = content.image.getFile();
   notFoundIfNull(file);
   renderBinary(file);
 }
 public static void showContents() {
   List<Content> contents = Content.findAll();
   render(contents);
 }