code: private RequestArguments.Argument arg(Request R) {
        if( _arg != null ) return _arg;
        Class clzz = R.getClass();
        // An amazing crazy API from the JDK again.  Cannot search for protected
        // fields without either (1) throwing NoSuchFieldException if you ask in
        // a subclass, or (2) sorting through the list of ALL fields and EACH
        // level of the hierarchy.  Sadly, I catch NSFE & loop.
        while( true ) {
          try {
            Field field = clzz.getDeclaredField(_name);
            field.setAccessible(true);
            Object o = field.get(R);
            return _arg=((RequestArguments.Argument)o);
          }
          catch(   NoSuchFieldException ie ) { clzz = clzz.getSuperclass(); }
          catch( IllegalAccessException ie ) { break; }
          catch( ClassCastException ie ) { break; }
        }
        return null;
      }
docs: Specific accessors for input arguments.  Not valid for JSON output fields.