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Method Level @KafkaListener ​

Selection Criteria ​

Found methods will be selected for further processing only if @KafkaListener annotation is not empty.

Registration process ​

Each @KafkaListener annotation is considered as a separate channel

Operations registration process depends on @SendTo annotation usage.

Without @SendTo ​

java
@Component
public class MultiMessagesListener {

    @KafkaListener(topics = "messages.1", groupId = "group_1")
    @KafkaListener(topics = {"messages.2", "messages.3"}, groupId = "group_2")
    public void listen(Object message) {}

}

The next channels will be registered:

  • messages.1
  • messages.2
  • messages.3

With @SendTo ​

java
@Component
public class MultiMessagesListener {

    @KafkaListener(topics = "messages.1", groupId = "group_1")
    @KafkaListener(topics = {"messages.2", "messages.3"}, groupId = "group_2")
    @SendTo("messages.replies")
    public void listen(Object message) {}

}

The next channels will be registered:

  • messages.1
  • messages.2
  • messages.3
  • messages.replies

Messages registration ​

Without @SendTo ​

Each incoming message will be associated with chanel from @KafkaListener annotation

With @SendTo ​

When method is void, than each incoming message will be associated with chanel from @KafkaListener annotation

When method is non-void, than:

  • incoming messages will be associated with chanel from @KafkaListener annotation
  • outgoing messages will be associated with chanel from @SendTo annotation