Do I have to use @Payload spring annotation to read Kafka message-CodePudding

Spring for Apache Kafka 2.8.4 under https://docs.spring.io/spring-kafka/reference/html shows some of the listener methods with @Payload annotation next to the message and some do not. For example:

@KafkaListener(id = "cat", topics = "myTopic",
          containerFactory = "kafkaManualAckListenerContainerFactory")
public void listen(String data, Acknowledgment ack) {
    ...
    ack.acknowledge();
}

and

@KafkaListener(id = "qux", topicPattern = "myTopic1")
public void listen(@Payload String foo,
        @Header(name = KafkaHeaders.RECEIVED_MESSAGE_KEY, required = false) Integer key,
        @Header(KafkaHeaders.RECEIVED_PARTITION_ID) int partition,
        @Header(KafkaHeaders.RECEIVED_TOPIC) String topic,
        @Header(KafkaHeaders.RECEIVED_TIMESTAMP) long ts
        ) {
    ...
}

What approach is correct? I am testing both and see no diference.

CodePudding user response：

The short answer is No, you don't have to use it.

The long answer is "it depends"; if you want to do some validation on Kafka message, @Payload will help you with this like the following from documentation

To configure the @KafkaListener to handle null payloads, you must use the @Payload annotation with required = false. If it is a tombstone message for a compacted log, you usually also need the key so that your application can determine which key was “deleted”. The following example shows such a configuration:

I would prefer to use a normal String instead, this way you are away from some known parsing issues like Poison Pill by offloading the responsibility to the application side instead of the built-in way handled by Spring.