Question

我有一个用Spring Boot 2.0.2编写的Kafka消费者应用程序。当我在监听器中收到消息时，出现以下错误：

Caused by: org.springframework.messaging.converter.MessageConversionException: failed to resolve class name. Class not found [com.test.demo.domain.Account]; nested exception is java.lang.ClassNotFoundException: com.test.demo.domain.Account

Producer中对象的类名是＆＃34; com.test.demo.domain.Account ＆＃34;但我在消费者中有不同的包装和类名。

当我重新打包消费者的类名以匹配生产者时，一切正常。但是，我相信我不应该这样做。

有谁知道这个问题？

====更新====

我的制作人代码：

@Bean public ProducerFactory<String, Account> accountProducerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    configProps.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName());
    configProps.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, JsonSerializer.class.getName());
    return new DefaultKafkaProducerFactory<>(configProps); }

@Bean public KafkaTemplate<String, Account> accountKafkaTemplate() {
    ProducerFactory<String, Account> factory = accountProducerFactory();

    return new KafkaTemplate<>(factory); }

消费者代码：

public ConsumerFactory<String, Account> accountConsumerFactory() {
    Map<String, Object> configProps = new HashMap<>();
    configProps.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapAddress);
    configProps.put(ConsumerConfig.GROUP_ID_CONFIG, groupName);
    configProps.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
    configProps.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, BytesDeserializer.class.getName());
    return new DefaultKafkaConsumerFactory<>(configProps);
}

@Bean
public KafkaListenerContainerFactory<?> kafkaJsonListenerContainerFactory() {
    ConcurrentKafkaListenerContainerFactory<String, Account> factory = new ConcurrentKafkaListenerContainerFactory<>();
    factory.setConsumerFactory(accountConsumerFactory());
    factory.setMessageConverter(new StringJsonMessageConverter());
    return factory;
}

例外：

org.springframework.kafka.listener.ListenerExecutionFailedException: Listener method could not be invoked with the incoming message
Endpoint handler details:
Method [public void com.kconsumer.accountconsumer.service.AccountConsumer.accountListener(com.kconsumer.accountconsumer.domain.Account)]
Bean [com.kconsumer.accountconsumer.service.AccountConsumer@444cc791]; nested exception is org.springframework.messaging.converter.MessageConversionException: Cannot handle message; nested exception is org.springframework.messaging.converter.MessageConversionException: Cannot convert from [java.lang.String] to [com.kconsumer.accountconsumer.domain.Account] for GenericMessage [payload={"id":"5b079d0b340d9ef2ac9b6f02","name":"test-400","version":0}, headers={kafka_offset=0, kafka_consumer=org.apache.kafka.clients.consumer.KafkaConsumer@6a0a6b0b, kafka_timestampType=CREATE_TIME, kafka_receivedMessageKey=5b079d0b340d9ef2ac9b6f02, kafka_receivedPartitionId=0, kafka_receivedTopic=ktest, kafka_receivedTimestamp=1527225611820, __TypeId__=[B@2f92e17a}], failedMessage=GenericMessage [payload={"id":"5b079d0b340d9ef2ac9b6f02","name":"test-400","version":0}, headers={kafka_offset=0, kafka_consumer=org.apache.kafka.clients.consumer.KafkaConsumer@6a0a6b0b, kafka_timestampType=CREATE_TIME, kafka_receivedMessageKey=5b079d0b340d9ef2ac9b6f02, kafka_receivedPartitionId=0, kafka_receivedTopic=ktest, kafka_receivedTimestamp=1527225611820, __TypeId__=[B@2f92e17a}]
    at org.springframework.kafka.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:257)

Answer 1

如果您使用的是StringDeserializer，请使用ByteArrayDserializer或StringJsonMessageConverter并在应用程序上下文中添加@Bean @KafkaListener(...) public void listen(Account account) { ... }。

则...

@SpringBootApplication
public class So50478267Application {

    public static void main(String[] args) {
        SpringApplication.run(So50478267Application.class, args);
    }

    @Bean
    public ApplicationRunner runner(KafkaTemplate<String, Account1> template) {
        return args -> template.send("so50478267", new Account1("foo.inc"));
    }

    @KafkaListener(id = "listen", topics = "so50478267")
    public void listen(Account2 account) {
        System.out.println(account);
    }

    @Bean
    public StringJsonMessageConverter jsonConverter() {
        return new StringJsonMessageConverter();
    }

    @Bean
    public NewTopic topic() {
        return new NewTopic("so50478267", 1, (short) 1);
    }

    public static class Account1 {

        private final String customer;

        public Account1(String customer) {
            this.customer = customer;
        }

        public String getCustomer() {
            return this.customer;
        }

    }

    public static class Account2 {

        private String customer;

        public Account2() {
            super();
        }

        public String getCustomer() {
            return this.customer;
        }

        public void setCustomer(String customer) {
            this.customer = customer;
        }

        @Override
        public String toString() {
            return "Account2 [customer=" + this.customer + "]";
        }

    }

}

...将所需的帐户类型传递给转换器。

请参阅the documentation。

修改

您不需要连接工厂，启动会检测转换器并为您连接。

以下是一个例子：

spring.kafka.consumer.auto-offset-reset=earliest spring.kafka.consumer.enable-auto-commit=false spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer

和

UsersController def create user = User.find_or_create_by(email: params[:user][:email]) cookies.permanent.signed[:user_id] = user.id session[:user_id] = user.id # for users/edit temporary render json: user end

Answer 2

你是如何反序列化你的Kafka记录对象的？如果你使用spring-kafka API中的反序列化器，比如StringDeserializer，JsonDeserializer ......我认为不可能改变记录对象的包名。

如果您自己为Kafka记录编写自定义Serdes，那么您可以通过重写ObjectInputStream的方法 readClassDescriptor（）来在反序列化逻辑中执行此操作。请找到示例代码here。

Kafka使用者

2 个答案: