[keycloak-user] How do I get KeycloakSecurityContext to be set in the httpServletRequest in Keycloak's account-linking doc?

Hi. In Keycloak's account-linking <http://www.keycloak.org/docs/3.2/server_development/topics/identity-broke... documentation, there's a code snippet: KeycloakSecurityContext session = (KeycloakSecurityContext) httpServletRequest.getAttribute(KeycloakSecurityContext.class.getName()). Why would the KeycloakSecurityContext be set in the httpServletRequest? Where does this code should run? In what context? Thanks. * Also posted the question in SO: https://stackoverflow.com/questions/46409356/how-do-i-get-keycloaksecurit...