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https://issues.apache.org/jira/browse/KAFKA-3519?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Guozhang Wang resolved KAFKA-3519.
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Resolution: Fixed
Issue resolved by pull request 1204
[https://github.com/apache/kafka/pull/1204]
> 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: streams
> Reporter: Guozhang Wang
> Assignee: Guozhang Wang
> Labels: api
> 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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