Hi, Thanks for the response. We are trying to implement something similar as discussed in the following SFO post.
http://stackoverflow.com/questions/27535668/spark-streaming-groupbykey-and-updatestatebykey-implementation We are doing it in java while accepted answer(second answer) in this post is in Scala. We wrote our java code taking this scala code as reference. But we are getting exception in highlighted line i.e. in return Optional.of(events.add(state.toString());); Specifically, it happens when we call events.add() final Function2<List<String>, Optional<List<String>>, Optional<List<String>>> updateFunc = new Function2<List<String>, Optional<List<String>>, Optional<List<String>>>() { public Optional<List<String>> call(List<String> events, Optional<List<String>> state) throws Exception { // TODO Auto-generated method stub if(state.toString()==null) return Optional.of(events); else { //UnsupportedOperationException here return Optional.of(events.add(state.toString());); } } }; Please let us know if you need more details. Unfortunately we are not in a position to share whole code. Thanks Regards, Anand/Yogesh From: Tathagata Das [mailto:t...@databricks.com] Sent: Friday, October 16, 2015 1:22 PM To: Chandra Mohan, Ananda Vel Murugan Cc: user Subject: Re: Get the previous state string in Spark streaming Its hard to help without any stacktrace associated with UnsupportedOperationException. On Thu, Oct 15, 2015 at 10:40 PM, Chandra Mohan, Ananda Vel Murugan <ananda.muru...@honeywell.com<mailto:ananda.muru...@honeywell.com>> wrote: One of my co-worker(Yogesh) was trying to get this posted in spark mailing and it seems it did not get posted. So I am reposting it here. Please help. Hi, I am new to Spark and was trying to do some experiments with it. I had a JavaPairDStream<String, List<String>> RDD. I want to get the list of string from its previous state. For that I use updateStateByKey function as follows: final Function2<List<String>, Optional<List<String>>, Optional<List<String>>> updateFunc = new Function2<List<String>, Optional<List<String>>, Optional<List<String>>>() { public Optional<List<String>> call(List<String> arg0, Optional<List<String>> arg1) throws Exception { // TODO Auto-generated method stub if(arg1.toString()==null) return Optional.of(arg0); else { arg0.add(arg1.toString()); return Optional.of(arg0); } } }; I want the function to append the new list of string to the previous list and return the new list. But I am not able to do so. I am getting the C error. Can anyone which help me out in getting the desired output?
