如何重用 Spring Kafka 代码来设置多个监听器？

Question

If my application has one listener, the case is dead simple:

I will configure spring.kafka.* , Spring Boot will parse the configuration to KafkaPropeties and initialize all required beans.

But I have two listeners, let say one saves records to file and second to database. I would like reuse as much as possible Spring Boot conventions.

I would like to configure file.kafka.* and db.kafka.* , parse these configuration to 2 KafkaProperties beans:

@ConfigurationProperties("file.kafka")
@Bean(autowireCandidate = false)
KafkaProperties fileKafkaProperties() {
  return new KafkaProperties();
}

@ConfigurationProperties("db.kafka")
@Bean(autowireCandidate = false)
KafkaProperties dbKafkaProperties() {
  return new KafkaProperties();
}

and finally create 2 ConcurrentKafkaListenerContainerFactory : db and file, respectively.

The problem is that to apply KafkaPropeties to ConcurrentKafkaListenerContainerFactory I need ConcurrentKafkaListenerContainerFactoryConfigurer . But the ConcurrentKafkaListenerContainerFactoryConfigurer is not enough public to be initialized with KafkaPropeties .

Is there a public access limitation problem on ConcurrentKafkaListenerContainerFactoryConfigurer or do I something wrong?

Answer 1

From KafkaProperties you can build ConsumerFactory

@Bean
@ConditionalOnMissingBean(name="kafkaConsumerFactory")
public ConsumerFactory<String, String> kafkaConsumerFactory(KafkaProperties kafkaProperties) {
return new DefaultKafkaConsumerFactory<>(
        kafkaProperties.buildConsumerProperties(),
        new StringDeserializer(),
        new StringDeserializer());
}

Use ConsumerFactory to build ConcurrentKafkaListenerContainerFactory

@Bean
KafkaListenerContainerFactory<ConcurrentMessageListenerContainer<Integer, String>>
                kafkaListenerContainerFactory() {
ConcurrentKafkaListenerContainerFactory<Integer, String> factory =
                        new ConcurrentKafkaListenerContainerFactory<>();
factory.setConsumerFactory(kafkaConsumerFactory());
factory.setConcurrency(3);
factory.getContainerProperties().setPollTimeout(3000);
return factory;
}