Spring云Kafka流反序列化问题由以下原因引起：java.lang.ClassCast异常：ClassName无法转换为ClassName

Question

我正在尝试使用Spring云Kafka流绑定器来使用来自主题的Avro消息，但无法修复此class Cast异常。

这是我的代码：

  @Bean
  public Consumer<KStream<EventKey, Event>> process(){
    return input -> {
      input.peek(((key, value) -> logger.info("key value: "+ key.toString()+" value: "+value.toString())));
      logger.info("Received:" + input);
    };
  }

  @Bean
  public Serde<EventKey> avroInSerde(){
    final SpecificAvroSerde<EventKey> avroInSerde = new SpecificAvroSerde<>();
    Map<String, Object> serdeProperties = new HashMap<>();
    return avroInSerde;
  }

  @Bean
  public Serde<Event> avroOutSerde(){
    final SpecificAvroSerde<Event> avroOutSerde = new SpecificAvroSerde<>();
    return avroOutSerde;
  }

粘合剂:

spring:
  application:
    name: ${applicaton-name}
  cloud:
    stream:
      function:
        definition: process
      bindings:
        process-in-0:
          destination: ${input-topic-name}
          contentType: application/Avro
        process-out-0:
          destination: ${enriched-topic-name}
          contentType: application/Avro
      binding-retry-interval: 30
      kafka:
        streams:
          binder:
            brokers: ${kafka-broker}
            application-id: ${consumer-group-name}
            auto-create-topics: false
            auto-add-partitions: false
            configuration:
              processing.guarantee: at_least_once
              auto.offset.reset: earliest
              schema.registry.url: ${kafka-schema-registry}
              auto-register-schema: false
              security.protocol: SSL
              useNativeEncoding: true
              specific.avro.reader: true

错误：

Note that although incorrect Serdes are a common cause of error, the cast exception might have another cause (in user code, for example). For example, if a processor wires in a store, but casts the generics incorrectly, a class cast exception could be raised during processing, but the cause would not be wrong Serdes.
    at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:146)
    at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:236)
    at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:216)
    at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:168)
    at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:96)
    at org.apache.kafka.streams.processor.internals.StreamTask.lambda$process$1(StreamTask.java:679)
    at org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:836)
    at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:679)
    at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:1033)
    at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:690)
    at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:551)
    at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:510)
Caused by: java.lang.ClassCastException: EventKey cannot be cast to EventKey
    at org.apache.kafka.streams.kstream.internals.KStreamPeek$KStreamPeekProcessor.process(KStreamPeek.java:42)
    at org.apache.kafka.streams.processor.internals.ProcessorNode.lambda$process$2(ProcessorNode.java:142)
    at org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:836)
    at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:142)

我尝试了本链接中提到的两种方法https://spring.io/blog/2019/12/04/stream-processing-with-spring-cloud-stream-and-apache-kafka-streams-part-3-data-deserialization-and-serialization但没有运气

我错过了什么吗？

Answer 1

原因：java.lang.ClassCastException:EventKey无法强制转换为EventKey

这可能是类装入器问题;由于反序列化器和消费者 Bean 由不同的类加载器加载，您是否使用 Spring DevTools？

使用spry-kafka，可以通过显式创建消费者工厂并将反序列化器注入其中来避免这种情况。

使用 spring-cloud-stream（从版本 3.0.6 开始），您可以提供一个 ClientFactoryCustomizer bean 并注入反序列化程序实例（定义为 @Beans，以便它们使用相同的类加载器）。

或者，停止使用DevTools。