code: private OptionalEntity<File> getTargetFile(final String fileName) {
          final File baseDir = new File(getServletContext().getRealPath("/"));
          final File targetFile = new File(getServletContext().getRealPath(fileName));
          final List<File> fileList = getAccessibleFileList(baseDir);
          for (final File file : fileList) {
              if (targetFile.equals(file)) {
                  return OptionalEntity.of(targetFile);
              }
          }
          return OptionalEntity.empty();
      }
docs: ============