Can IngressController replace Frontend role such as Httpd or Nginx?

Hi, I am trying to get used to Istio.
Judging from various functions of Istio(faultinjection, traffic route and whitelist), is it necessary to use webservers like nginx or httpd as a frontend role working as proxy for backend like tomcat?

IngressController can receive users’ requests as a loadbalancer and it can route traffic according to url. Therefore, I thought IngressController can substitute webserver frontend (Of course, when static web pages are required, front webservers are needed).

How about recommended WAS environment with nginx and tomcat, I can find only bookinfo example. Are there other cases with Istio? or some communities and sites which show reperfences?

Yes this has been a main feature of Istio for some time now (years). You can replace nxing or any other ingress proxy with the Istio ingress gateway.

Istio Ingress-Gateway will replace components like Nginx Ingress Operator or the Traefik counterpart.

But that is filling up the Ingress part of your cluster. Your container being served by Istio, wether thru are frontend (static, or Nodejs perhaps) or backend services (PHP, Node, Java and so on) will still need a server within the image to deliver the data.