kafka-streams-Materialized.adoc

Materialized — Metadata for State Store Materialized View

Materialized provides optional parameters that describe how to materialize a state store (as a KTable):

• Name of the state store

• StoreSupplier

Materialized is used for the following:

• In High-Level Stream Processing DSL to create KTables and global KTables

• KTable API

• For count, reduce and aggregate operators in KGroupedStream, KGroupedTable, SessionWindowedKStream, TimeWindowedKStream

Materialized is created using the factory methods.

Materialized<K, V, S> as(
  String storeName)
Materialized<K, V, KeyValueStore<Bytes, byte[]>> as(
  KeyValueBytesStoreSupplier supplier)
Materialized<K, V, SessionStore<Bytes, byte[]>> as(
  SessionBytesStoreSupplier supplier)
Materialized<K, V, WindowStore<Bytes, byte[]>> as(
  WindowBytesStoreSupplier supplier)
Materialized<K, V, S> with(
  Serde<K> keySerde,
  Serde<V> valueSerde)

A Materialized instance can futher be configured using the "with" methods.

Table 1. Materialized’s with Methods

Method	Description
withCachingDisabled	Materialized<K, V, S> withCachingDisabled() Creates a Materialized with caching disabled
withCachingEnabled	Materialized<K, V, S> withCachingEnabled() Creates a Materialized with caching enabled
withKeySerde	Materialized<K, V, S> withKeySerde(Serde<K> keySerde) Creates a Materialized with the Serde for keys
withLoggingDisabled	Materialized<K, V, S> withLoggingDisabled() Creates a Materialized with logging disabled
withLoggingEnabled	Materialized<K, V, S> withLoggingEnabled(Map<String, String> config) Creates a Materialized with logging enabled
withRetention	Materialized<K, V, S> withRetention(Duration retention)
withValueSerde	Materialized<K, V, S> withValueSerde(Serde<V> valueSerde) Creates a Materialized with the Serde for values

Scala API for Kafka Streams

Scala API for Kafka Streams makes the optional Materialized metadata an implicit parameter in the KStream API.

Moreover, ImplicitConversions object defines materializedFromSerde implicit method that creates a Materialized instance with the key and value Serde objects available in implicit scope.

Scala API for Kafka Streams also defines Materialized object with `with` and as factory methods that use implicit key and value Serde objects.