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For instance, aggregate grouped (by key) values together in a list to do other subsequent operations on the collection.

Public Interfaces

• New class class org.apache.kafka.common.serialization.ListSerializer which  which implements the Serializer<List<T>> Serializer<List<T>> interface
• New class class org.apache.kafka.common.serialization.ListDeserializer which implements Deserializer<List<T>> implements Deserializer<List<T>> interface
• New subclass ListSerde in ListSerde<T> in org.apache.kafka.common.serialization.Serdes Serdes which creates new serde based on ListSerializer and on ListSerializer and ListDeserializer classes

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• New method public static <T> Serde<List<T>> ListSerde(Serde<T> innerSerde) in org.apache.kafka.common.serialization.Serdes

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•  class

Proposed Changes

This KIP proposes adding new ListSerializer and ListDeserializer classes as well as support for the new classes into the Serdes class. This will allow using List<T> Serde directly from Consumers, Producers and Streams.

List<T> serialization and deserialization will be done through repeatedly calling a serializer/deserializer for each entry provided by passed generic T's Serde. For example, if you want to create List of Strings serde, you will have to declare new ListSerde<>(Serdes.String()), in this case  then serializer/deserializer of String Serde StringSerde will be used to serialize/deserialize each entry in `List<String>`.

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