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I want to write a consumer method which subscribes to a topic using KafkaListener.

I found an answer which suggested this -

@KafkaListener(id = "foo", topics = "dead-out")
public void dlq(Message<?> in) {
    System.out.println("DLQ:" + in);
}

Now, in the annotation 'topics' is the name of the subscribed topic. But what is 'id' field ? Or is there a better way?

Your help is appreciated.

shreyas.k
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1 Answers1

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@KafkaListener has nothing to do with Spring Cloud Stream; it is in the Spring for Apache Kafka project (which Spring Cloud Stream uses for its Kafka binder).

See the javadocs

    /**
     * The unique identifier of the container managing for this endpoint.
     * <p>If none is specified an auto-generated one is provided.
     * <p>Note: When provided, this value will override the group id property
     * in the consumer factory configuration, unless {@link #idIsGroup()}
     * is set to false.
     * <p>SpEL {@code #{...}} and property place holders {@code ${...}} are supported.
     * @return the {@code id} for the container managing for this endpoint.
     * @see org.springframework.kafka.config.KafkaListenerEndpointRegistry#getListenerContainer(String)
     */
    String id() default "";

The id is also used to get the listener container from the KafkaListenerEndpointRegistry bean so you can stop() and start() it.

If you want to use spring-cloud-stream instead; read its documentation.

Gary Russell
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  • You can start by using this quick start - https://cloud.spring.io/spring-cloud-static/spring-cloud-stream/3.0.4.RELEASE/reference/html/spring-cloud-stream.html#_quick_start. Should take no more then 5 min. – Oleg Zhurakousky May 13 '20 at 14:38