How to convert a KStream to a KTable in Kafka Streams

If you have a KStream and you need to convert it to a KTable, KStream.toTable does the trick. Prior to the introduction of this method in Apache Kafka 2.5, a dummy aggregation operation was required.

As a concrete example, consider a topic with string keys and values. To convert the stream to a KTable:

  KTable<String, String> convertedTable = builder.stream(INPUT_TOPIC, Consumed.with(stringSerde, stringSerde))
    .toTable(Materialized.as("stream-converted-to-table"));