Deserialize kafka messages in KafkaConsumer using springboot - json

Question

I have a springboot app that listen kafka messages and convert them to object
#KafkaListener(topics = "test", groupId = "group_id")
public void consume(String message) throws IOException {
ObjectMapper objectMapper = new ObjectMapper();
Hostel hostel = objectMapper.readValue(message, Hostel.class);
}
I woder if it is possible to do ti directly
#KafkaListener(topics = "test", groupId = "group_id")
public void consume(Hostel hostel) throws IOException {
}

Answer 1

You can do it using spring-kafka. But then you need to use a custom deserializer (or a JsonDeserializer) in the container factory
#KafkaListener(topics = "test", groupId = "my.group", containerFactory = "myKafkaFactory")
fun genericMessageListener(myRequest: MyRequest, ack: Acknowledgment) {
//do Something with myRequest
ack.acknowledge()
}
Your ContainerFactory will look something like
#Bean
fun myKafkaFactory(): ConcurrentKafkaListenerContainerFactory<String, MyRequest> {
val factory = ConcurrentKafkaListenerContainerFactory<String, MyRequest>()
factory.consumerFactory = DefaultKafkaConsumerFactory(configProps(), StringDeserializer(), MyRequestDeserializer())
factory.containerProperties.ackMode = ContainerProperties.AckMode.MANUAL
return factory
}
Your Deserialiser will look like
public class MyRequestDeserializer implements Deserializer {
private static ObjectMapper objectMapper = new ObjectMapper();
#Override
public void configure(Map map, boolean b) {
}
#Override
public MyRequest deserialize(String arg0, byte[] msgBytes) {
try {
return objectMapper.readValue(new String(msgBytes), MyRequest.class);
} catch (IOException ex) {
log.warn("JSON parse/ mapping exception occurred. ", ex);
return new MyRequest();
}
}
#Override
public void close() {
log.debug("MyRequestDeserializer closed");
}
}
Alternatively, you can use the default JsonDeserializer as given in spring docs