java - Spring kafka @KafkaListener 没有被调用

Question

我正在尝试使用 spring-kafka 将 kafka 与我的 Spring boot (v2.0.6.RELEASE) 应用程序集成。现在我想要一个消费者和一个生产者。我让生产者工作得很好，我可以看到消息通过控制台消费者发送到主题。我无法让消费者代码工作，当 kafka 主题中出现新消息时，它不会被调用。

这是我的 kafka 配置类:

@Configuration
@EnableKafka
public class KafkaConfiguration {

    @Bean
    public Map<String, Object> producerConfigs() {
        Map<String, Object> props = new HashMap<>();

        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, <path to my custom serializer>);
        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");

        return props;
    }

    @Bean
    public Map<String, Object> consumerConfigs(){
        Map<String, Object> props = new HashMap<>();

        props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, "org.apache.kafka.common.serialization.StringSerializer");
        props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, <path to my custom deserializer>);
        props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
//        props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");

        return props;
    }

    @Bean
    public ConsumerFactory<String, List<MyMessage>> consumerFactory() {
        return new DefaultKafkaConsumerFactory<>(consumerConfigs());
    }

    @Bean
    public KafkaListenerContainerFactory<ConcurrentMessageListenerContainer<String, List<MyMessage>>> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, List<MyMessage>> factory = new ConcurrentKafkaListenerContainerFactory<>();
        factory.setConsumerFactory(consumerFactory());
        return factory;
    }

    @Bean
    public ProducerFactory<String, List<MyMessage>> producerFactory() {
        return new DefaultKafkaProducerFactory<>(producerConfigs());
    }

    @Bean
    public KafkaTemplate<String, List<MyMessage>> kafkaTemplate() {
        return new KafkaTemplate<>(producerFactory());
    }

}

这是我的 pom 依赖项:

<dependency>
  <groupId>org.springframework.kafka</groupId>
  <artifactId>spring-kafka</artifactId>
</dependency>

以及消费者代码:

@Slf4j
public class MyMessageConsumer {

    @KafkaListener(topicPattern = "test_topic")
    public void receive(List<MyMessage> myMessages){
        log.info("Received payload {}", myMessages);
    }
}

我正在计算机上运行 kafka，正如我所说 - 我可以看到控制台消费者中出现的消息。我的基于 Spring 的消费者收不到消息的原因可能是什么？

编辑: 这是解串器类:

public class TagEventDeserializer implements Deserializer<List<MyMessage>> {
    @Override
    public void configure(Map map, boolean b) {

    }

    @Override
    public List<MyMessage> deserialize(String s, byte[] bytes) {
        ObjectMapper objectMapper = new ObjectMapper();
        List<MyMessage> myMessages = null;
        try{
            myMessages = objectMapper.readValue(bytes , List.class);
        } catch (Exception e){
            e.printStackTrace();
        }
        return myMessages;
    }

    @Override
    public void close() {

    }
}

Answer 1

因为您的类 MyMessageConsumer 由于缺少构造型注释而未被 Spring 扫描，因此向此类添加 @Component 例如将解决您的问题:

@Slf4j
@Component
public class MyMessageConsumer {

    @KafkaListener(topicPattern = "test_topic")
    public void receive(List<MyMessage> myMessages){
        log.info("Received payload {}", myMessages);
    }
}

我认为在 @KafkaListner 注释中指定消费者组是个好主意