Serde with custom aggregater

Can any please let me know what is the best way to set the serde for the materialized stores with custom aggregater class Following is my aggregation

groupByKey() .windowedBy(TimeWindows.of(1000).until(1000)) .aggregate(DataAggregate::new, (key, value, aggregate) -> { aggregate.add(1); return aggregate; }, Materialized.as("aggstore"))

DataAggregate is the class that holds the aggregation - I need to save that to aggstore

but the default serde I am using is the spring.cloud.stream.kafka.streams.binder.configuration.commit.interval.ms=1000 spring.cloud.stream.kafka.streams.binder.configuration.default.key.serde=org.apache.kafka.common.serialization.Serdes$StringSerde spring.cloud.stream.kafka.streams.binder.configuration.default.value.serde=org.apache.kafka.common.serialization.Serdes$StringSerde

exception I am getting is Exception in thread "eventsin-00aacb65-5224-4b2f-858b-fe98bd134b7c-StreamThread-1" java.lang.ClassCastException: sample.streamprocessor.dataaggregator.DataAggregate cannot be cast to java.lang.String at org.apache.kafka.common.serialization.StringSerializer.serialize(StringSerializer.java:28) at org.apache.kafka.streams.state.StateSerdes.rawValue(StateSerdes.java:178) at org.apache.kafka.streams.state.internals.MeteredWindowStore.put(MeteredWindowStore.java:96) at org.apache.kafka.streams.kstream.internals.KStreamWindowAggregate$KStreamWindowAggregateProcessor.process(KStreamWindowAggregate.java:122)

[sobychacko]

@vinu - You cannot directly use the JsonSerde class like that. However, you can extend from this in your project and use it in properties. For instance,

FooSerde extends JsonSerde<Foo> {}

and then spring.cloud.stream.kafka.streams.binder.configuration.default.value.serde=FooSerde

[sobychacko]

@vinu what @olegz and @orchesio said above. You need to pass the proper key and value Serde when you materialize the state store. Since you are not passing any Serdes for that, the defaults are kicking in and running into that exception. You need to use the Materialized.with... methods for that. If your DataAggregate is json friendly, you can use the JsonSerde provided as part of spring-kafka and pass a reference of this to your aggregation. Hope this helps.