/** Return true if the file is a valid jar plugin file */
 public static boolean isValidJarPlugin(final File file) {
   try {
     try (final JarInputStream jarInputStream = new JarInputStream(new FileInputStream(file))) {
       final Manifest manifest = jarInputStream.getManifest();
       if (null == manifest) {
         return false;
       }
       final Attributes mainAttributes = manifest.getMainAttributes();
       validateJarManifest(mainAttributes);
     }
     return true;
   } catch (IOException | InvalidManifestException e) {
     log.error(file.getAbsolutePath() + ": " + e.getMessage());
     return false;
   }
 }