== Sample 1
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 3 times and, after retries are exhausted, sends a bad message to a dead-letter topic.
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"}`
