Question

我有一个kafka监听器，它正确接收数据但EventData ss = consumerRecord.value()给出了ClassCastException。

我正在使用默认的弹簧启动设置。我不确定它是如何正确接收消息的，当我尝试使用时，它会给出异常。

 @KafkaListener(topics = "${kafka.topic.event.model.message}")
    public void receive(ConsumerRecord<String, EventData> consumerRecord)  throws IOException, ClassNotFoundException {
        LOGGER.info("received payload='{}'", consumerRecord.value());
        EventData ss = consumerRecord.value();
    }

它给出了例外：

Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to com.betstars.betsyncadapter.app.kafka.message.EventData
    at com.betstars.betsyncadapter.app.kafka.message.KafkaMessageListenerForEventModel.receive(KafkaMessageListenerForEventModel.java:26) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_151]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_151]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_151]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_151]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:180) ~[spring-messaging-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:112) ~[spring-messaging-4.3.9.RELEASE.jar:4.3.9.RELEASE]
    at org.springframework.kafka.listener.adapter.HandlerAdapter.invoke(HandlerAdapter.java:48) ~[spring-kafka-1.1.6.RELEASE.jar:na]
    at org.springframework.kafka.listener.adapter.MessagingMessageListenerAdapter.invokeHandler(MessagingMessageListenerAdapter.java:174) ~[spring-kafka-1.1.6.RELEASE.jar:na]
    ... 10 common frames omitted

Answer 1

Spring Boot Apache Kafka自动配置默认使用StringDeserializer value：

https://github.com/spring-projects/spring-boot/blob/v2.0.0.RC1/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/kafka/KafkaProperties.java#L287

您应该考虑为org.springframework.kafka.support.serializer.JsonDeserializer用例使用EventData：

spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer
spring.kafka.consumer.properties.spring.json.value.default.type=com.your.EventData

虽然是春季引导2.0。

对于以前的版本，您应使用JsonDeserializer扩展程序：

public class EventDataJsonDeserializer extends JsonDeserializer<EventData> { }

属性：

spring.kafka.consumer.value-deserializer = com.your.EventDataJsonDeserializer

Answer 2

还要仔细检查是否为消费者配置了“ properties.specific.avro.reader：true”

Kafka Listener正在提供ClassCastException

2 个答案: