Configuring custom Kafka Consumer Deserializer in application.properties file. [spring boot]

Question

I want to consume avro messages and deserialize them without using the Confluent schema registry. I have the schema locally. So, for that, I followed this https://medium.com/@mailshine/apache-avro-quick-example-in-kafka-7b2909396c02 for Consumer part only. Now, I want to configure this deserializer in the application.properties file (the Spring boot way). I tried adding spring.kafka.consumer.value-deserializer=com.example.AvroDeserializer But this results in error saying "Could not find a public no-argument constructor for com.example.AvroDeserializer". Is there any way to call the constructor with argument from application.properties configuration. Or Do I need to configure this in Code instead of properties?

Thanks in advance!!

Gary Russell · Accepted Answer · 2021-09-15 13:25:29Z

1

You can do it using properties, but you have to do it via the configure method (with a no-arg constructor) - this is because Kafka instantiates the deserializer, not Spring.

See the org.springframework.kafka.support.serializer.JsonDeserializer source code for an example.

Otherwise, you can just inject your Deserializer into the consumer factory...

@Bean
MyDeserializer(DefaultKafkaConsumerFactory<String, Foo> factory) {
    MyDeserializer<Foo> deser = new MyDeserializer<>(...);
    factory.setValueDeserializer(deser);
    return deser;
}

answered Sep 15, 2021 at 13:25

Gary Russell

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