Invoking a kafka consumer based on some condition - spring-boot

Question

Suppose if there is a class A which is consuming data from kafka consumer C1 and based on the data from consumer C1, I need to start consuming from consumer C2.
Is there a way to do it?

Answer 1

Here's one way:
#SpringBootApplication
public class So62160012Application {
public static void main(String[] args) {
SpringApplication.run(So62160012Application.class, args);
}
#Autowired
private KafkaListenerEndpointRegistry registry;
#Autowired
private KafkaTemplate<String, String> template;
#KafkaListener(id = "so62160012-1", topics = "so62160012-1")
public void listen1(String in) {
System.out.println("one: " + in);
template.send("so62160012-2", in);
if (in.contains("startC2")) {
this.registry.getListenerContainer("so62160012-2").start();
}
}
#KafkaListener(id = "so62160012-2", topics = "so62160012-2", autoStartup = "false")
public void listen2(String in) {
System.out.println("two: " + in);
}
#Bean
public NewTopic topic1() {
return TopicBuilder.name("so62160012-1").partitions(1).replicas(1).build();
}
#Bean
public NewTopic topic2() {
return TopicBuilder.name("so62160012-2").partitions(1).replicas(1).build();
}
#Bean
public ApplicationRunner runner() {
return args -> {
IntStream.range(0, 10)
.map(i -> {
try {
Thread.sleep(2000);
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
return i;
})
.forEach(i -> this.template.send("so62160012-1",
"foo" + i + (i == 5 ? "startC2" : "")));
};
}
}
Hopefully self-explanatory.