question: protected void validateConfig ( ) { A . notNull ( getStreamer ( ) , "Streamer" ) ; A . notNull ( getIgnite ( ) , "Ignite" ) ; A . notNull ( endpointUrl , "Twitter Streaming API endpoint" ) ; A . ensure ( getSingleTupleExtractor ( ) != null || getMultipleTupleExtractor ( ) != null , "Twitter extractor" ) ; String followParam = apiParams . get ( SITE_USER_ID_KEY ) ; A . ensure ( followParam != null && followParam . matches ( "^(\\d+,? ?)+$" ) , "Site streaming endpoint must provide 'follow' param with value as comma separated numbers" ) ; }
target:  Validates config at start.