KafkaBindingRebalanceListener Bean not autowired by KafkaMessageChannelBinder Bean - spring-boot

Question

Documentation is pretty straight forward which suggests exposing a Bean of type KafkaBindingRebalanceListener and onPartitiosnAssigned method would be called internally. I'm trying to do the same and somehow while spring framework creates its KafkaMessageChannelBinder Bean the ObjectProvider.getIfUnique() always return null as it not able to find the required bean. It seems when application starts SpringFramework strats creating its Beans first and isnt able to find the Rebalance Listener Bean as it is not yet created. Following are the three code snippets from project. Please help if im missing anything to instruct application to create Beans in application package first before going to Spring Framework.
RebalanceListener
package io.spring.dataflow.sample.seekoffset.config;
import org.apache.kafka.clients.consumer.Consumer;
import org.apache.kafka.common.TopicPartition;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.stream.binder.kafka.KafkaBindingRebalanceListener;
import org.springframework.stereotype.Component;
import java.util.Collection;
#Component
public class KafkaRebalanceListener implements KafkaBindingRebalanceListener {
Logger logger = LoggerFactory.getLogger(SeekOffsetConfig.class);
#Override
public void onPartitionsAssigned(String bindingName, Consumer<?, ?> consumer, Collection<TopicPartition> partitions, boolean initial) {
logger.debug("onPartitionsAssigned");
}
}
ConfigClass
package io.spring.dataflow.sample.seekoffset.config;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.annotation.StreamListener;
import org.springframework.cloud.stream.messaging.Sink;
import org.springframework.messaging.Message;
#EnableBinding(Sink.class)
public class SeekOffsetConfig {
Logger logger = LoggerFactory.getLogger(SeekOffsetConfig.class);
#StreamListener(Sink.INPUT)
public void receiveMessage(Message<String> message) {
logger.debug("receiveMessage()");
}
}
ApplicationClass
package io.spring.dataflow.sample.seekoffset;
import io.spring.dataflow.sample.seekoffset.config.KafkaRebalanceListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.ComponentScan;
#SpringBootApplication
public class SeekOffsetApplication {
Logger logger = LoggerFactory.getLogger(SeekOffsetApplication.class);
public static void main(String[] args) {
SpringApplication.run(SeekOffsetApplication.class, args);
}
}

Answer 1

What version are you using? This works fine for me with Boot 2.3.2 and Hoxton.SR6:
#SpringBootApplication
#EnableBinding(Sink.class)
public class So63157778Application {
public static void main(String[] args) {
SpringApplication.run(So63157778Application.class, args);
}
#StreamListener(Sink.INPUT)
public void listen(String in) {
System.out.println(in);
}
#Bean
KafkaBindingRebalanceListener rebal() {
return new KafkaBindingRebalanceListener() {
#Override
public void onPartitionsAssigned(String bindingName, Consumer<?, ?> consumer,
Collection<TopicPartition> partitions, boolean initial) {
System.out.println(bindingName + " assignments: " + partitions + ", initial call :" + initial);
}
};
}
}
input assignments: [input-0], initial call :true
This works for me too:
#SpringBootApplication
#EnableBinding(Sink.class)
public class So63157778Application {
public static void main(String[] args) {
SpringApplication.run(So63157778Application.class, args);
}
#StreamListener(Sink.INPUT)
public void listen(String in) {
System.out.println(in);
}
}
#Component
class Foo implements KafkaBindingRebalanceListener {
#Override
public void onPartitionsAssigned(String bindingName, Consumer<?, ?> consumer,
Collection<TopicPartition> partitions, boolean initial) {
System.out.println(bindingName + " assignments: " + partitions + ", initial call :" + initial);
}
}