[keycloak-user] Get current user through JACC

I'm testing a javaee webapp inside a Wildfly with a 4.5.0.Final keycloak adapter installed. The authentication is ok but now I would get in my web app the current user id. Using this code: javax.security.jacc.PolicyContext.getContext("javax.security.auth.Subject.container"); I get null. How I miss to receive the user id? You can test the sample of the keycloak quickstart from https://github.com/keycloak/keycloak-quickstarts/tree/latest/app-authz-je... and add that code in the Controller class where do you want.