Use @SpanTag to assign value from object

Question

@NewSpan
public void validateUser(@SpanTag("userName" userDto.getName()) UserDto userDto) 

I want to add a span tag userName whose value is userDto.getName() using @SpanTag annotation. I do not want to pass username as a method param as it would be duplicate since dto is already being passed & above way is not supported. Going through the documentation, I did not find a way to achieve this, is there a workaround? https://cloud.spring.io/spring-cloud-sleuth/reference/html/

Tried above approach but did not work, I do not want to do this by creating any bean.