question: public Resolution doWithCredential ( String userId , Callable < Resolution > action ) { Credential credential = loadCredential ( userId ) ; if ( credential != null ) { try { return action . call ( ) ; } catch ( Exception e ) { throw new RuntimeException ( e ) ; } } return new RedirectResolution ( computeAuthorizationUrl ( ) ) ; }
target:  Executes an action if the user's credential is known, otherwise redirects to the authorization page.