code: public String getStorageServiceOption(ApplicationDefinition appDef) {
          String ssName = appDef.getOption(CommonDefs.OPT_STORAGE_SERVICE);
          if (Utils.isEmpty(ssName)) {
              ssName = DoradusServer.instance().getDefaultStorageService();
              appDef.setOption(CommonDefs.OPT_STORAGE_SERVICE, ssName);
          }
          return ssName;
      }
docs: Get the given application's StorageService option. If none is found, assign and
  return the default. Unlike {@link #getStorageService(ApplicationDefinition)}, this
  method will not throw an exception if the storage service is unknown or has not
  been initialized.
  
  @param   appDef  {@link ApplicationDefinition} of an application.
  @return          The application's declared or assigned StorageService option.