This sample demonstrates a simple producer and consumer; the producer sends objects of type Foo1 and the consumer receives objects of type Foo2 (the objects have the same field, foo).
The producer uses a JsonSerializer; the consumer uses the StringDeserializer that is automatically configured by Spring Boot, together with a StringJsonMessageConverter which converts to the type of the listener method argument.
Run the application and use curl to send some data:
$ curl -X POST http://localhost:8080/send/foo/bar
Console:
2018-11-05 10:03:40.216 INFO 39766 --- [ fooGroup-0-C-1] com.example.Application : Received: Foo2 [foo=bar]
The consumer is configured with a SeekToCurrentErrorHandler which replays failed messages up to 2 times, each after a 1 second delay and, after retries are exhausted, sends a bad message to a dead-letter topic.
$ curl -X POST http://localhost:8080/send/foo/fail
A second @KafkaListener consumes the raw JSON from the message.
2018-11-05 10:12:32.552 INFO 41635 --- [ fooGroup-0-C-1] com.example.Application : Received: Foo2 [foo=fail]
2018-11-05 10:12:32.561 ERROR 41635 --- [ fooGroup-0-C-1] essageListenerContainer$ListenerConsumer : Error handler threw an exception
…
2018-11-05 10:12:33.033 INFO 41635 --- [ fooGroup-0-C-1] com.example.Application : Received: Foo2 [foo=fail]
2018-11-05 10:12:33.033 ERROR 41635 --- [ fooGroup-0-C-1] essageListenerContainer$ListenerConsumer : Error handler threw an exception
…
2018-11-05 10:12:33.537 INFO 41635 --- [ fooGroup-0-C-1] com.example.Application : Received: Foo2 [foo=fail]
2018-11-05 10:12:43.359 INFO 41635 --- [ dltGroup-0-C-1] com.example.Application : Received from DLT: {"foo":"fail"}