Retrieve Keycloak user data using received access token
I am developing a WildFly-Backend (in Java) that accepts HTTP requests (from a custom Frontend) that are signed with the user's Keycloak bearer access token through the "Authorization" HTTP header. The Backend connection itself is already secured with the Keycloak adapter for WildFly, but internally, I want to check who the user is (user groups, name, etc.) and return verying responses. I figured that it would be possible to just send this data from the Frontend, but then people could easily fake the request once they have an access token. Is there a way to retrieve things like user data while