What is Spring Kafka, and how do you produce and consume messages with it?

Messaging

Spring for Apache Kafka wraps the raw Kafka client APIs in Spring-idiomatic abstractions — a `KafkaTemplate` for producing messages (send a value, optionally with a key, to a named topic), and `@KafkaListener` on a method for consuming, which Spring Boot auto-configures to start a listener container polling the specified topic and invoking the annotated method for each received record.

Intermediate5 min

Kafka delivers each message to only one consumer within the same consumer group (enabling horizontal scaling of consumers processing a shared workload), but delivers a copy of every message to each distinct consumer group independently — so two @KafkaListener methods with different `groupId` values both receive every message, while multiple instances sharing the same groupId split the workload between them. Getting groupId wrong is a very common source of 'why did I get duplicate/missing messages' bugs.

What is Spring Kafka, and how do you produce and consume messages with it?

Consumer Group ID Determines Whether Messages Are Shared or Duplicated

Producing and Consuming with Spring Kafka