Java 春云溪卡夫卡>；使用来自合流REST代理的Avro消息

我有以下情况：

• Producer通过Confluent的REST代理（在Confluent的模式注册表上注册模式）向Kafka主题发送Avro编码的消息，如中所述
• 启用Spring Cloud Stream的消息侦听主题以获取新消息

我的应用程序如下所示：

@SpringBootApplication
@EnableBinding(Sink.class)
public class MyApplication {
  private static Logger log = LoggerFactory.getLogger(MyApplication.class);

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

  @StreamListener(Sink.INPUT)
  public void myMessageSink(MyMessage message) {
    log.info("Received new message: {}", message);
  }
}

spring.cloud.stream.bindings.input.destination=myTopic
spring.cloud.stream.bindings.input.group=${spring.application.name}
spring.cloud.stream.bindings.input.contentType=application/*+avro

而MyMessage是由Avro根据Avro模式创建的类

我的application.properties如下所示：

@SpringBootApplication
@EnableBinding(Sink.class)
public class MyApplication {
  private static Logger log = LoggerFactory.getLogger(MyApplication.class);

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

  @StreamListener(Sink.INPUT)
  public void myMessageSink(MyMessage message) {
    log.info("Received new message: {}", message);
  }
}

spring.cloud.stream.bindings.input.destination=myTopic
spring.cloud.stream.bindings.input.group=${spring.application.name}
spring.cloud.stream.bindings.input.contentType=application/*+avro

现在我的问题是，每次收到新消息时，都会引发以下异常：

org.springframework.messaging.MessagingException: Exception thrown while invoking MyApplication#myMessageSink[1 args]; nested exception is org.apache.avro.AvroRuntimeException: Malformed data. Length is negative: -27
    at org.springframework.cloud.stream.binding.StreamListenerAnnotationBeanPostProcessor$StreamListenerMessageHandler.handleRequestMessage(StreamListenerAnnotationBeanPostProcessor.java:316) ~[spring-cloud-stream-1.1.0.RELEASE.jar:1.1.0.RELEASE]
    at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:109) ~[spring-integration-core-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127) ~[spring-integration-core-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.integration.dispatcher.AbstractDispatcher.tryOptimizedDispatch(AbstractDispatcher.java:116) ~[spring-integration-core-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:148) ~[spring-integration-core-4.3.2.RELEASE.jar:4.3.2.RELEASE]
    ...
Caused by: org.apache.avro.AvroRuntimeException: Malformed data. Length is negative: -27
    at org.apache.avro.io.BinaryDecoder.doReadBytes(BinaryDecoder.java:336) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.io.BinaryDecoder.readString(BinaryDecoder.java:263) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.io.ResolvingDecoder.readString(ResolvingDecoder.java:201) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:430) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readString(GenericDatumReader.java:422) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readMapKey(GenericDatumReader.java:335) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readMap(GenericDatumReader.java:321) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:177) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.specific.SpecificDatumReader.readField(SpecificDatumReader.java:116) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:230) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:174) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:152) ~[avro-1.8.1.jar:1.8.1]
    at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:144) ~[avro-1.8.1.jar:1.8.1]
    at org.springframework.cloud.stream.schema.avro.AbstractAvroMessageConverter.convertFromInternal(AbstractAvroMessageConverter.java:91) ~[spring-cloud-stream-schema-1.1.0.RELEASE.jar:1.1.0.RELEASE]
    at org.springframework.messaging.converter.AbstractMessageConverter.fromMessage(AbstractMessageConverter.java:175) ~[spring-messaging-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.messaging.converter.CompositeMessageConverter.fromMessage(CompositeMessageConverter.java:67) ~[spring-messaging-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.messaging.handler.annotation.support.PayloadArgumentResolver.resolveArgument(PayloadArgumentResolver.java:117) ~[spring-messaging-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:112) ~[spring-messaging-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:138) ~[spring-messaging-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.messaging.handler.invocation.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:107) ~[spring-messaging-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.cloud.stream.binding.StreamListenerAnnotationBeanPostProcessor$StreamListenerMessageHandler.handleRequestMessage(StreamListenerAnnotationBeanPostProcessor.java:307) ~[spring-cloud-stream-1.1.0.RELEASE.jar:1.1.0.RELEASE]
    ... 35 common frames omitted

据我所知，问题在于合流堆栈将消息架构的ID作为消息有效负载的一部分包含在内，客户机应该在架构ID之后开始读取实际的Avro消息。 似乎我需要配置Kafka绑定以使用Confluent的KafkaAvroDeserializer，但我不知道如何实现这一点

（我可以使用Confluent的avro控制台消费者很好地检索消息，因此avro编码似乎没有问题）

我还尝试使用@EnableSchemaRegistry注释并配置ConfluentSchemaRegistryClient bean，但在我看来，这只控制模式的存储/检索位置，而不是实际的反序列化

---

这是否应该在某种程度上起作用？

当设置每个绑定的

属性
spring.cloud.stream.kafka.bindings.input.consumer.configuration.value.deserializer
以拥有
Confluent的Kafkaavroderializer类名时，它是否起作用？
回答了我自己的问题。我现在所做的是实现一个MessageConverter，它只删除任何消息的前4个字节，然后再将它们传递给Avro解码器。代码主要取自spring cloud stream的AbstractAvroMessageConverter：

public class ConfluentAvroSchemaMessageConverter extends AvroSchemaMessageConverter {

public ConfluentAvroSchemaMessageConverter() {
    super(new MimeType("application", "avro+confluent"));
}

@Override
protected Object convertFromInternal(Message<?> message, Class<?> targetClass, Object conversionHint) {
    Object result = null;
    try {
        byte[] payload = (byte[]) message.getPayload();

        // byte array to contain the message without the confluent header (first 4 bytes)
        byte[] payloadWithoutConfluentHeader = new byte[payload.length - 4];
        ByteBuffer buf = ByteBuffer.wrap(payload);
        MimeType mimeType = getContentTypeResolver().resolve(message.getHeaders());
        if (mimeType == null) {
            if (conversionHint instanceof MimeType) {
                mimeType = (MimeType) conversionHint;
            }
            else {
                return null;
            }
        }

        // read first 4 bytes and copy the rest to the new byte array
        // see https://groups.google.com/forum/#!topic/confluent-platform/rI1WNPp8DJU
        buf.getInt();
        buf.get(payloadWithoutConfluentHeader);

        Schema writerSchema = resolveWriterSchemaForDeserialization(mimeType);
        Schema readerSchema = resolveReaderSchemaForDeserialization(targetClass);
        DatumReader<Object> reader = getDatumReader((Class<Object>) targetClass, readerSchema, writerSchema);
        Decoder decoder = DecoderFactory.get().binaryDecoder(payloadWithoutConfluentHeader, null);
        result = reader.read(null, decoder);
    }
    catch (IOException e) {
            throw new MessageConversionException(message, "Failed to read payload", e);
    }
    return result;

}

公共类Confluent AvroschemMessageConverter扩展了AvroschemMessageConverter{
公共汇流AVROSCHEMA消息转换器（）{
super（新的MimeType（“应用程序”、“avro+合流”）；
}
@凌驾
受保护的对象convertFromInternal（消息消息、类targetClass、对象转换提示）{
对象结果=空；
试一试{
字节[]有效载荷=（字节[]）消息。getPayload（）；
//字节数组，用于包含不包含合流标头的消息（前4个字节）
byte[]payloadWithoutConfluentHeader=新字节[payload.length-4]；
ByteBuffer buf=ByteBuffer.wrap（有效载荷）；
MimeType-MimeType=getContentTypeResolver（）.resolve（message.getHeaders（））；
if（mimeType==null）{
if（MimeType的转换提示实例）{
mimeType=（mimeType）转换提示；
}
否则{
返回null；
}
}
//读取前4个字节，并将其余字节复制到新的字节数组中
//看https://groups.google.com/forum/#！主题/汇合平台/rI1WNPp8DJU
buf.getInt（）；
buf.get（无汇合头的有效载荷）；
Schema writerSchema=resolverewriterschemaforderserialization（mimeType）；
Schema readerSchema=ResolveReaderSchemaForderSerialization（targetClass）；
DatumReader=getDatumReader（（类）targetClass，readerSchema，writerSchema）；
Decoder Decoder=DecoderFactory.get（）.binaryDecoder（payloadWithoutConfluentHeader，null）；
结果=reader.read（空，解码器）；
}
捕获（IOE异常）{
抛出新的MessageConversionException（消息“读取有效负载失败”，e）；
}
返回结果；
}

然后，我通过application.properties将传入卡夫卡主题的内容类型设置为application/avro+confluent

这至少可以让我检索使用合流堆栈编码的消息，但它当然不会以任何方式与模式注册表交互。
看起来
KafkaMessageChannelBinder
的使用者端点总是使用
ByteArraydSerializer
作为键/值序列化程序。这可能是
KafkaMessageCh的结果默认情况下，annelBinder
的生产者使用的是
ByteArraySerializer
。对于非基于Spring云流的生产者，消费者应该能够使用上述属性覆盖所需的反序列化器。不幸的是，我没有这样做，我已经尝试过了。从我在中看到的情况来看，反序列化器被硬编码为默认的ByteArrayDeserializer.yeah，请在此处创建问题：。我们可以从那里跟踪它。谢谢！已创建问题：