Package org.apache.kafka.streams.kstream
Interface Aggregator<K,V,VA>
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- Type Parameters:
K
- key typeV
- input value typeVA
- aggregate value type
public interface Aggregator<K,V,VA>
TheAggregator
interface for aggregating values of the given key. This is a generalization ofReducer
and allows to have different types for input value and aggregation result.Aggregator
is used in combination withInitializer
that provides an initial aggregation value.Aggregator
can be used to implement aggregation functions like count.- See Also:
Initializer
,KGroupedStream.aggregate(Initializer, Aggregator)
,KGroupedStream.aggregate(Initializer, Aggregator, Materialized)
,TimeWindowedKStream.aggregate(Initializer, Aggregator)
,TimeWindowedKStream.aggregate(Initializer, Aggregator, Materialized)
,SessionWindowedKStream.aggregate(Initializer, Aggregator, Merger)
,SessionWindowedKStream.aggregate(Initializer, Aggregator, Merger, Materialized)
,Reducer
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description VA
apply(K key, V value, VA aggregate)
Compute a new aggregate from the key and value of a record and the current aggregate of the same key.
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