This sample demonstrates a simple producer and a multi-method consumer; the producer sends objects of types Foo1 and Bar1 and the consumer receives objects of type Foo2 and Bar2 (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 required type of the listener method argument. We can’t infer the type in this case (because the type is used to choose the method to call). We therefore configure type mapping on the producer and consumer side. See the application.yml for the producer side and the converter bean on the consumer side.

The MultiMethods @KafkaListener has 3 methods; one for each of the known objects and a fallback default method for others.

Run the application and use curl to send some data:

$ curl -X POST http://localhost:8080/send/foo/bar

$ curl -X POST http://localhost:8080/send/bar/baz

$ curl -X POST http://localhost:8080/send/unknown/xxx

Console:

Received: Foo2 [foo=bar] Received: Bar2 [bar=baz] Received unknown: xxx