Guozhang Wang created KAFKA-3519:
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Summary: Refactor Transformer templates to return the same
strong-typed value.
Key: KAFKA-3519
URL: https://issues.apache.org/jira/browse/KAFKA-3519
Project: Kafka
Issue Type: Bug
Components: kafka streams
Reporter: Guozhang Wang
Assignee: Guozhang Wang
Fix For: 0.10.0.0
Currently the Transformer interface's template is:
{code}
R transform(K key, V value);
{code}
While all its usage requires a key-value pair, and hence constructing the
object as:
{code}
new Transformer<K, V, KeyValue<K1, V1>>
{code}
Since we expect Transformer to be only used in the Streams DSL, which is
supposed to return another key-value pair streams, it's better to define its
template just as
{code}
public interface Transformer<K, V, K1, V1> {
KeyValue<K1, V1> transform(K key, V value);
}
{code}
Also, we can allow punctuate() to also return a nullable KeyValue<K1, V1> pair,
and let the implementation to forward to downstream processor only when the
returned pair is not null.
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