Great. So you have an index named contacts but it is empty.
Either you created manually.
Or Logstash created it.
If the later, then it means that Logstash did not read any "event" from the database.
I'd recommend to change the logstash output to stdout just to check if anything is read from the database.
Or check logstash logs. May be something is wrong.
I wonder if this is correct:
jdbc_driver_library => "C:\Users\Hakansu\Downloads\ojdbc6.jar"
And should not be:
jdbc_driver_library => "C:/Users/Hakansu/Downloads/ojdbc6.jar"
But it might be better to ask in #logstash forum then...