导致IllegalArgumentException的KStream.Map中的Null值：有效负载不能为Null

Question

我正在创建一个spring cloud Kafka流应用程序。我有一个输入主题和一个输出主题，我试图使用KStream.map函数对输入主题应用KStream键值转换操作
问题如果转换后的值为null，该函数将抛出IllegalArgumentException
我的问题是:
1:异常的原因？尽管文档中说：“忽略具有空键或空值的输入记录”
2:处理无状态/有状态操作中异常的最佳实践？一个try/catch围绕整个处理计划是否就足够了？或者我应该在每个转换函数中都有一个try/catch（例如，筛选、映射、联接、减少）？

spring:
  application:
    name:kafka-streams-test
  cloud.stream:
    kafka.streams:
      binder:
        brokers: localhost:9093
        configuration:
          commit.interval.ms: 1000
          security.protocol: SASL_PLAINTEXT
          sasl.mechanism: GSSAPI
          sasl.kerberos.service.name: kafka
        serdeError: logAndContinue
      bindings:
        streams-words-input:
          consumer:
            application-id: Input-Words
        streams-words-output:
          consumer:
            application-id: Output-Words
    bindings:
      streams-words-input:
        destination: streams-words-input
      streams-words-output:
        destination: streams-words-output

@StreamListener()
@SendTo("streams-words-output")
public KStream<String, Long> createWords(
    @Input("streams-words-input") final KStream<String, String> wordsInput){
    return wordsInput
            .map((key,value) -> KeyValue.pair(key, null));
}

java.lang.IllegalArgumentException: Payload must not be null
at org.springframework.util.Assert.notNull(Assert.java:198)
at org.springframework.messaging.support.MessageBuilder.<init>(MessageBuilder.java:57)
at org.springframework.messaging.support.MessageBuilder.withPayload(MessageBuilder.java:179)
at org.springframework.cloud.stream.binder.kafka.streams.KafkaStreamsMessageConversionDelegate.lambda$serializeOnOutbound$0(KafkaStreamsMessageConversionDelegate.java:86)
at org.springframework.cloud.stream.binder.kafka.streams.KafkaStreamsMessageConversionDelegate$$Lambda$743/1725151361.apply(Unknown Source)
at org.apache.kafka.streams.kstream.internals.AbstractStream$2.apply(AbstractStream.java:87)
at org.apache.kafka.streams.kstream.internals.KStreamMapValues$KStreamMapProcessor.process(KStreamMapValues.java:40)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50)
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:126)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90)
at org.apache.kafka.streams.kstream.internals.KStreamMap$KStreamMapProcessor.process(KStreamMap.java:42)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50)
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:126)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90)
at org.apache.kafka.streams.kstream.internals.KStreamMapValues$KStreamMapProcessor.process(KStreamMapValues.java:41)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50)
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:126)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90)
at org.apache.kafka.streams.kstream.internals.KStreamPassThrough$KStreamPassThroughProcessor.process(KStreamPassThrough.java:33)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50)
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:122)
at org.apache.kafka.streams.kstream.internals.KStreamBranch$KStreamBranchProcessor.process(KStreamBranch.java:48)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50)
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:129)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90)
at org.apache.kafka.streams.kstream.internals.KStreamMapValues$KStreamMapProcessor.process(KStreamMapValues.java:41)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:50)
at org.apache.kafka.streams.processor.internals.ProcessorNode.runAndMeasureLatency(ProcessorNode.java:244)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:133)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:143)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:126)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:90)
at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:87)
at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:302)
at org.apache.kafka.streams.processor.internals.AssignedStreamsTasks.process(AssignedStreamsTasks.java:94)
at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:409)
at org.apache.kafka.streams.processor.internals.StreamThread.processAndMaybeCommit(StreamThread.java:964)
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:832)
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:767)
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:736)

Answer 1

您看到的异常来自Spring消息传递的长期规则--“没有有效负载为空的消息”。换句话说，如果没有什么要交流，就没有消息要发送。

也就是说，KStream和它如何处理这种情况显然有一个问题，所以我建议在Kafka Binder中提出一个问题。同时，您可以轻松地向管道添加filter操作，以过滤掉空值。