question: private void pickOnlyProvider ( ) throws ServletException { try { Entry < OAuthLoginProvider > loginProvider = Iterables . getOnlyElement ( loginProviders ) ; defaultAuthPlugin = loginProvider . getPluginName ( ) ; defaultAuthProvider = loginProvider . getExportName ( ) ; } catch ( NoSuchElementException e ) { throw new ServletException ( "No OAuth login provider installed" ) ; } catch ( IllegalArgumentException e ) { } }
target:  Picks the only installed OAuth provider. If there is a multiude of providers available, the actual provider must be determined from the authentication request.