class PermissionExtractorRegistry {

   public PermissionExtractor getPermissionExtractor(PlatformMessage message) {
      PermissionExtractor extractor = extractors.get(message.getMessageType());
      return extractor == null ? fallbackExtractor : extractor;
   }

   @Inject public  PermissionExtractorRegistry(Map<String,PermissionExtractor> extractors);

}