code: protected ActionForward invokeActionMethod( Method method, Object arg )
          throws Exception
      {
          return invokeActionMethod( method, arg, getRequest(), getActionMapping() );
      }
docs: Invoke the given action handler method, passing it an argument if appropriate.
  
  @param method the action handler method to invoke.
  @param arg the form-bean to pass; may be <code>null</code>.
  @return the ActionForward returned by the action handler method.
  @throws Exception if an Exception was raised in user code.