spring-boot/spring-boot-samples/spring-boot-sample-kafka/src/main/resources/application.properties

spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=testGroup
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
spring.kafka.consumer.properties.spring.json.trusted.packages=sample.kafka
spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer