How to get spring boot default Kafka consumer object

Question

My configurations for Kafka consumer are in the application.yaml file. I know that if I only have 1 consumer, I don't need to create a consumerFactory bean and it would be set by spring by default. I need to test my consumer so I need to access the consumer object in my test file and I don't want to config it again (I want to use the default configuration in the application.yaml) file to create a consumer object. How is this possible?

Answer 1

Spring Boot provides a comprehensive enough auto-configuration for Spring Kafka: https://docs.spring.io/spring-boot/docs/2.4.3/reference/html/spring-boot-features.html#boot-features-kafka.

There is this set of beans you can inject into your test class:

• KafkaTemplate<?, ?> kafkaTemplate
• ProducerListener<Object, Object> kafkaProducerListener
• ConsumerFactory<?, ?> kafkaConsumerFactory
• ProducerFactory<?, ?> kafkaProducerFactory
• KafkaTransactionManager<?, ?> kafkaTransactionManager
• KafkaJaasLoginModuleInitializer kafkaJaasInitializer
• KafkaAdmin kafkaAdmin
• ConcurrentKafkaListenerContainerFactoryConfigurer kafkaListenerContainerFactoryConfigurer
• ConcurrentKafkaListenerContainerFactory<?, ?> kafkaListenerContainerFactory
• KafkaStreamsConfiguration defaultKafkaStreamsConfig
• KafkaStreamsFactoryBeanConfigurer kafkaStreamsFactoryBeanConfigurer

So, to get a KafkaConsumer in your test, you need to autowire a ConsumerFactory and call its createConsumer() and you'll get a fresh instance based on the configuration properties.