JSONDeserializer for Kafka consumer config

How to deserialize JSON data which has no schema and pass it’s config to ConsumerConfig. I am using plain java.

I tried using KafkaJSONschemaDeserializer but I don’t want to use schema registry.
Deserialized data I want to send it in Ignite Cache Table. So I want it to be a POJO object.
What can be the best solution for this?