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https://issues.apache.org/jira/browse/KAFKA-4672?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xavier Léauté updated KAFKA-4672:
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Description:
Variance changes introduced in KIP-100 cause compilation failures with lambda
expression in Java 8.
To my knowledge this only affects methods taking suppliers of functions
KStreams.transform(TransformerSupplier<...>, String...)
KStreams.transformValues(ValueTransformerSupplier<...>)
prior to the changes it was possible to write
streams.transform(MyTransformer::new)
streams.transformValues(MyValueTransformer::new)
where MyTransformer and MyValueTransformer extend Transformer and
ValueTransformer respectively.
After the changes the Java compiler is unable to infer correct return types for
the lambda expression.
was:
Variance changes introduced in KIP-100 cause compilation failures with lambda
expression in Java 8.
To my knowledge this only affects methods taking suppliers of functions
KStreams.transform(TransformerSupplier<...>, String...)
KStreams.transformValues(ValueTransformerSupplier<...>)
KStreams.process(ProcessorSupplier<...>)
prior to the changes it was possible to write
streams.process(MyProcessor::new)
streams.transform(MyTransformer::new)
etc.
where MyProcessor and MyTransformer extend Processor and Transformer
respectively.
After the changes the Java compiler is unable to infer correct types for the
lambda expression.
> KIP-100 api changes break Java 8 lambda expressions in some cases
> ------------------------------------------------------------------
>
> Key: KAFKA-4672
> URL: https://issues.apache.org/jira/browse/KAFKA-4672
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 0.10.2.0
> Reporter: Xavier Léauté
> Assignee: Xavier Léauté
> Fix For: 0.10.2.0
>
>
> Variance changes introduced in KIP-100 cause compilation failures with lambda
> expression in Java 8.
> To my knowledge this only affects methods taking suppliers of functions
> KStreams.transform(TransformerSupplier<...>, String...)
> KStreams.transformValues(ValueTransformerSupplier<...>)
> prior to the changes it was possible to write
> streams.transform(MyTransformer::new)
> streams.transformValues(MyValueTransformer::new)
> where MyTransformer and MyValueTransformer extend Transformer and
> ValueTransformer respectively.
> After the changes the Java compiler is unable to infer correct return types
> for the lambda expression.
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