无法使用传入消息调用 Kafka 侦听器方法

Question

我通过使用 Spring Boot 应用程序将 JSON 数组转换为 Kafka Producer 中的 toString() 来发送 JSON 数组，但在 Consumer 中出现以下错误：

org.springframework.kafka.listener.ListenerExecutionFailedException: 无法使用传入消息调用侦听器方法 端点处理程序详细信息： 方法 [public void com.springboot.service.KafkaReciever.recieveData(com.springboot.model.Student,java.lang.String) 抛出 java.lang.Exception] 豆 [com.springboot.service.KafkaReciever@5bb3d42d];嵌套异常是 org.springframework.messaging.converter.MessageConversionException： 无法处理消息；嵌套异常是 org.springframework.messaging.converter.MessageConversionException： 无法从 [java.lang.String] 转换为 [com.springboot.model.Student] 用于 GenericMessage [有效载荷=[com.springboot.model.Student@5e40dc31, com.springboot.model.Student@235e68b8], headers={kafka_offset=45, kafka_receivedMessageKey=null, kafka_receivedPartitionId=0, kafka_receivedTopic=myTopic-kafkasender}], 失败消息=通用消息 [有效载荷=[com.springboot.model.Student@5e40dc31, com.springboot.model.Student@235e68b8], headers={kafka_offset=45, kafka_receivedMessageKey=null, kafka_receivedPartitionId=0, kafka_receivedTopic=myTopic-kafkasender}]

配置文件：

@Configuration
@EnableKafka
public class KafkaConsumerConfig {

    @Value("${kafka.boot.server}")
    private String kafkaServer;

    @Value("${kafka.consumer.group.id}")
    private String kafkaGroupId;

    @Bean
    public ConsumerFactory<String, String> consumerConfig() {

         Properties props = new Properties();

         props.put("bootstrap.servers", "localhost:9092");
         props.put(ConsumerConfig.GROUP_ID_CONFIG, kafkaGroupId);
         props.put("message.assembler.buffer.capacity", 33554432);
         props.put("max.tracked.messages.per.partition", 24);
         props.put("exception.on.message.dropped", true);
         props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
         props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class);
         props.put("segment.deserializer.class", DefaultSegmentDeserializer.class.getName());

         return new DefaultKafkaConsumerFactory(props, null, new StringDeserializer());
    }

    @Bean
    public KafkaListenerContainerFactory<ConcurrentMessageListenerContainer<String, String>> kafkaListenerContainerFactory() {
        ConcurrentKafkaListenerContainerFactory<String, String> listener = new ConcurrentKafkaListenerContainerFactory<>();
        listener.setConsumerFactory(consumerConfig());
        return listener;
    }
}

接收文件：

@Service
public class KafkaReciever {

    private static final Logger LOGGER = LoggerFactory.getLogger(KafkaReciever.class);

    @KafkaListener(topics = "${kafka.topic.name}", group = "${kafka.consumer.group.id}")
    public void recieveData(@Payload Student student, @Header(KafkaHeaders.MESSAGE_KEY) String messageKey) throws Exception{
        LOGGER.info("Data - " + student + " recieved");
    }
}

POST json：

 [{
        "studentId": "Q45678123",
        "firstName": "Anderson",
        "lastName": "John",
        "age": "12",
        "address": {
          "apartment": "apt 123",
          "street": "street Info",
          "state": "state",
          "city": "city",
          "postCode": "12345"
        }
    },
    {
        "studentId": "Q45678123",
        "firstName": "abc",
        "lastName": "xyz",
        "age": "12",
        "address": {
          "apartment": "apt 123",
          "street": "street Info",
          "state": "state",
          "city": "city",
          "postCode": "12345"
        }
    }]

我得到以下消费者输出：

[com.springboot.model.Student@5e40dc31, com.springboot.model.Student@235e68b8]

Answer 1

无法从 START_ARRAY 中反序列化 com.springboot.model.Student 的实例

如果使用 json 脱轨器，你有一个列表，而不是一个学生

@Payload List<Student> student

或者如果使用字符串脱轨器，你有一个 JSON 字符串，你必须手动解析它

receiveData(@Payload String student ... ) { 
    JsonNode data = new ObjectMapper().readTree(student); // for example, but should extract ObjectMapper to a field
}

关于您的其他输出，请参阅How do I print my Java object without getting "SomeType@2f92e0f4"?