Kafka auto-configuration does not support @SendTo

[garyrussell]

In order to support @SendTo (replies) in Kafka, the KafkaTemplate (if present) should be injected into the listener container factory...

	@KafkaListener(topics = "rjugUpcase", groupId = "rjug")
	@SendTo("rjug")
	public String upcase(String in) {
		System.out.println("upcase: " + in);
		return in.toUpperCase();
	}

java.lang.IllegalStateException: a KafkaTemplate is required to support replies
	at org.springframework.util.Assert.state(Assert.java:73) ~[spring-core-5.0.0.RELEASE.jar:5.0.0.RELEASE]
	at org.springframework.kafka.config.MethodKafkaListenerEndpoint.createMessageListener(MethodKafkaListenerEndpoint.java:136) ~[spring-kafka-2.0.0.RELEASE.jar:2.0.0.RELEASE]

See AbstractKafkaListenerContainerFactory.setReplyTemplate().

[SamD]

I'm still seeing this with 2.1.7.RELEASE

[snicoll]

@SamD 2.1.7.RELEASE is a bit vague (there's no such Spring Boot version so I can only assume that's a Spring Kafka version. Support was added in Spring Boot as of Spring Boot 2.0.0.M6 (see the milestone information on the right).

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[SamD]

@snicoll I went back and reviewed the reference and from that was able to determine the problem

When using @sendto, the ConcurrentKafkaListenerContainerFactory must be configured with a KafkaTemplate in its replyTemplate

It wasn't clear from the error this was the case.