Extract server name in Saml2 login callback

Question

I have a project setup with Saml2 login authentication and the response callback is handled with the method documented by spring.

      @GetMapping("/saml2/callback")
      public ResponseEntity saml2Login(Model model, @AuthenticationPrincipal        Saml2AuthenticatedPrincipal principal) {
    ...
}

Only problem is that I need to extract also the server name in this callback. How can I do this?