我正在尝试使用 Kafka Streams 对 CDC 数据执行 KTable-KTable 外键联接。我将读取的数据采用 Avro 格式，但它的序列化方式与其他行业序列化器/反序列化器（例如 Confluence 架构注册表）不兼容，因为架构标识符存储在标头中。
当我设置 KTables 的 Serdes 时，我的 Kafka Streams 应用程序最初运行，但最终失败，因为它在内部调用 Serializer 方法byte[] serialize(String topic, T data);而不是带有标头的方法（即byte[] serialize(String topic, Headers headers, T data)在包装序列化器 ValueAndTimestampSerializer 中。我正在使用的 Serdes 无法处理此问题并引发异常。
第一个问题是，有谁知道如何请求 Kafka Streams 在内部调用具有正确方法签名的方法吗？
我正在探索解决这个问题的方法，包括编写新的 Serdes，用消息本身中的模式标识符重新序列化。这可能涉及将数据重新复制到新主题或使用拦截器。
不过，我明白ValueTransformer可以访问中的标头ProcessorContext我想知道是否有更快的方法使用transformValues()。这个想法是首先将值读取为byte[]然后将值反序列化为转换器中的 Avro 类（请参见下面的示例）。然而，当我这样做时，我遇到了例外。
StreamsBuilder builder = new StreamsBuilder();
final KTable<Long, MySpecificClass> myTable = builder.table(
"my-topic",
Consumed.with(Serdes.Long(), Serdes.ByteArray())
)
.transformValues(MyDeserializerTransformer::new);
...
KTable<Long, JoinResult> joinResultTable = myTable.join(rightTable, MySpecificClass::getJoinKey, myValueJoiner);
joinResultTable.toStream()...
public class MyDeserializerTransformer implements
ValueTransformerWithKey<Long, byte[], MySpecificClass> {
MyAvroDeserializer deserializer;
ProcessorContext context;
@Override
public void init(ProcessorContext context) {
deserializer = new MyAvroDeserializer();
this.context = context;
}
@Override
public MySpecificClass transform(Long key, byte[] value) {
return deserializer.deserialize(context.topic(), context.headers(), value);
}
@Override
public void close() {
}
}
当我运行它时，我收到一个 ClassCastException。我该如何解决此问题或找到解决方法？我需要使用二级状态存储吗？
"class": "org.apache.kafka.streams.errors.StreamsException",
"msg": "ClassCastException invoking Processor. Do the Processor's input types match the deserialized types? Check the Serde setup and change the default Serdes in StreamConfig or provide correct Serdes via method parameters. Make sure the Processor can accept the deserialized input of type key: java.lang.Long, and value: org.apache.kafka.streams.kstream.internals.Change.\nNote 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.",
"stack": [
"org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:185)",
"org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forwardInternal(ProcessorContextImpl.java:281)",
"org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:260)",
"org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:219)",
"org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:172)",
"org.apache.kafka.streams.kstream.internals.KTableTransformValues$KTableTransformValuesProcessor.process(KTableTransformValues.java:117)",
"org.apache.kafka.streams.kstream.internals.KTableTransformValues$KTableTransformValuesProcessor.process(KTableTransformValues.java:87)",
"org.apache.kafka.streams.processor.internals.ProcessorAdapter.process(ProcessorAdapter.java:71)",
"org.apache.kafka.streams.processor.internals.ProcessorNode.lambda$process$2(ProcessorNode.java:181)",
"org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:884)",
"org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:181)",
...
"cause": {
"class": "java.lang.ClassCastException",
"msg": "class com.package.MySpecificClass cannot be cast to class [B (com.package.MySpecificClass is in unnamed module of loader 'app'; [B is in module java.base of loader 'bootstrap')",
"stack": [
"org.apache.kafka.common.serialization.ByteArraySerializer.serialize(ByteArraySerializer.java:19)",
"org.apache.kafka.streams.kstream.internals.foreignkeyjoin.ForeignJoinSubscriptionSendProcessorSupplier$UnbindChangeProcessor.process(ForeignJoinSubscriptionSendProcessorSupplier.java:102)",
"org.apache.kafka.streams.kstream.internals.foreignkeyjoin.ForeignJoinSubscriptionSendProcessorSupplier$UnbindChangeProcessor.process(ForeignJoinSubscriptionSendProcessorSupplier.java:72)",
"org.apache.kafka.streams.processor.internals.ProcessorAdapter.process(ProcessorAdapter.java:71)",
"org.apache.kafka.streams.processor.internals.ProcessorNode.lambda$process$2(ProcessorNode.java:181)",
"org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:884)",
"org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:181)",
