Custom Partitioner for Kafka Producer using application.properties | Absolute beginner guide

I almost gave up trying to configure Custom Partitioner Class using application.properties.

spring.kafka.producer.partitioner.class=classPath

Does not work after trying a hell lot of things. The partitioner.class remained null everytime.

I even tried to configure Custom Partitioner with code as well, but as my Kafka was on confluent cluster, I needed to provide sasl and jaas config via code, and I was not able to find any help online for that as well.

The correct configuration for it is:

spring.kafka.properties.partitioner.class=com.puneetchhabra.NotificationProcessor.config.CustomPartitioner

//Provide your complete classpath

Creating CustomPartitioner class

public class CustomPartitioner implements Partitioner {
    @Override
    public int partition(String topic, Object key, byte[] keyBytes, Object value, byte[] valueBytes, Cluster cluster) {
        //Your custom logic for partition
        //return partition index

        return 0; //every message sent to partition-0
    }

    @Override
    public void close() {
        // Perform any necessary cleanup
    }

    @Override
    public void configure(Map<String, ?> configs) {
        // Perform any necessary configuration
    }
}