kafka-streams-ValueTransformer.adoc

ValueTransformer — Stateful Record-by-Record Value Transformation

ValueTransformer is the contract in Kafka Streams for stateful mapping of a value to a new value of an arbitrary type.

package org.apache.kafka.streams.kstream;

interface ValueTransformer<V, VR> {
  void close();
  void init(final ProcessorContext context);
  VR transform(final V value);
  // deprecated
  VR punctuate(final long timestamp);
}

ValueTransformer is used when a stream (AbstractStream) is requested to toInternalValueTransformerSupplier.

Table 1. ValueTransformer Contract

Method	Description
close	Used when…​FIXME
init	Used when…​FIXME
transform	Used when…​FIXME
punctuate	DEPRECATED Use Punctuator interface