code: protected Locale resolveDefaultLocale(Translet translet) {
          Locale defaultLocale = getDefaultLocale();
          if (defaultLocale != null) {
              translet.getRequestAdapter().setLocale(defaultLocale);
              return defaultLocale;
          } else {
              return translet.getRequestAdapter().getLocale();
          }
      }
docs: Resolve the default locale for the given translet,
  Called if can not find specified Locale.
  
  @param translet the translet to resolve the locale for
  @return the default locale (never {@code null})
  @see #setDefaultLocale