kafka stream windowed count output unreadable - apache-kafka

Question

I am trying windowed count with word count example. It works fine except that output is partially unreadable.
Code:
StringSerializer stringSerializer = new StringSerializer();
StringDeserializer stringDeserializer = new StringDeserializer();
WindowedSerializer<String> windowedSerializer = new WindowedSerializer<>(stringSerializer);
WindowedDeserializer<String> windowedDeserializer = new WindowedDeserializer<>(stringDeserializer);
Serde<Windowed<String>> windowedSerde = Serdes.serdeFrom(windowedSerializer, windowedDeserializer);
TimeWindows window = TimeWindows.of(TimeUnit.MINUTES.toMillis(1)).advanceBy(TimeUnit.MINUTES.toMillis(1));
KStream<String, String> textLines = builder.stream("streams-plaintext-input");
KTable<Windowed<String>, Long> wordCounts = textLines
.flatMapValues(textLine -> Arrays.asList(textLine.toLowerCase().split("\\W+")))
.groupBy((key, word) -> word)
.windowedBy(window)
.count(Materialized.<String, Long, WindowStore<Bytes, byte[]>>as("counts-store"));
wordCounts.toStream().to("streams-plaintext-output", Produced.with(windowedSerde, Serdes.Long()));
KafkaStreams streams = new KafkaStreams(builder.build(), config);
streams.start();
Output:
kafka c[?? 1
yaya c[?? 1
kafka c[?? 2
I guess the unreadable part might be windows duration.
What can I do to let it readable?
EDIT:
Tried to use windowedSerde to print output:
KStream<Windowed<String>, Long> output = builder.stream("streams-plaintext-output");
output.print(windowedSerde, Serdes.Long());
It still doesn't work.

Answer 1

When reading from the topic you need to use a Deserializer appropriate for Serializer that was used to produce to the topic. In this case, you need to use the windowDeserializer, which you are already constructing like so:
WindowedDeserializer<String> windowedDeserializer = new WindowedDeserializer<>(stringDeserializer);