卡夫卡流-将KStream与KTable leftjoin（）结合使用时，出现NullPointerException

Question

我使用leftJoin使用表中的值来转换流消息（事务）。 我合并多个联接。 每次加入后，我都选择一个新密钥。 我在上一次连接中收到NullPointerException 。 筛选null键没有帮助。

Exception in thread "account-transactions-e0a66751-f65e-4ba0-947c-024b5d32f7c2-StreamThread-1" java.lang.NullPointerException at org.namematching.kafkastreams.transactiontransformation.TransactionTransformationStream.lambda$launchStream$14(TransactionTransformationStream.java:124)
at org.apache.kafka.streams.kstream.internals.KStreamKTableJoinProcessor.process(KStreamKTableJoinProcessor.java:58)
at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46)
at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:85)
at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:80)
at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:216)
at org.apache.kafka.streams.processor.internals.AssignedTasks.process(AssignedTasks.java:403)
at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:317)
at org.apache.kafka.streams.processor.internals.StreamThread.processAndMaybeCommit(StreamThread.java:942)
at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:822)
at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:774)
at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:744)

这是我的加入逻辑：

KStream<String,DoiTAccountTransaction> transactionsWithAccounts =
            transactionStream.leftJoin(accountTable,(v1,v2) -> { v1.setBeneficiaryBankAccount(v2.getOriginId()); return v1; }, Joined.with(Serdes.String(), transactionSerde, accountSerde))
            .selectKey((k,v) -> v.getTransactionCode());

KStream<String,DoiTAccountTransaction> transactionsWithTransactionCodes =
            transactionsWithAccounts.leftJoin(transactionCodesTable, (v1,v2) -> {v1.setTransactionCode(v2.getUid()); return v1; }, Joined.with(Serdes.String(), transactionSerde, transactionCodesSerde))
            .selectKey((k,v) -> v.getCurrency());

KStream<String,DoiTAccountTransaction> transactionsWithCurrencies =
            transactionsWithTransactionCodes.leftJoin(currenciesTable, (v1,v2) -> {v1.setCurrency(v2.getUid()); return v1;}, Joined.with(Serdes.String(), transactionSerde, currenciesSerde))
            .selectKey((k,v) -> v.getOriginalBeneficiary1());

KStream<String, DoiTAccountTransaction> transactionsWithPersons =
            transactionsWithCurrencies.leftJoin(personsTable,(v1,v2) -> {v1.setOriginalBeneficiary1(v2.getUid()); return v1;}, Joined.with(Serdes.String(), transactionSerde, personsSerde));


transactionsWithPersons.to("account-transactions-processed", Produced.with(Serdes.String(),transactionSerde));

上次加入失败。 筛选空键没有帮助。

Answer 1

是否有可能在那时的personTable中不存在该键的行，并且NPE来自v2.getUid（）表达式？

在访问联接的字段（所有v2字段）之前，对联接中的所有右侧对象进行不为null的检查会更安全。

https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Streams+Join+Semantics#KafkaStreamsJoinSemantics-KStream-KTableJoin