我刚刚开始使用scio和数据流。将我的代码尝试到一个输入文件中，效果很好。但是，当我向输入中添加更多文件时，出现以下异常：
java.lang.RuntimeException: org.apache.beam.sdk.coders.CoderException: cannot encode a null String
at org.apache.beam.runners.dataflow.worker.SimpleParDoFn$1.output(SimpleParDoFn.java:280)
at org.apache.beam.runners.core.SimpleDoFnRunner.outputWindowedValue(SimpleDoFnRunner.java:309)
at org.apache.beam.runners.core.SimpleDoFnRunner.access$700(SimpleDoFnRunner.java:77)
at org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:621)
at org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:609)
at com.spotify.scio.util.Functions$$anon$3.processElement(Functions.scala:158)
Caused by: org.apache.beam.sdk.coders.CoderException: cannot encode a null String
at org.apache.beam.sdk.coders.StringUtf8Coder.getEncodedElementByteSize(StringUtf8Coder.java:136)
at org.apache.beam.sdk.coders.StringUtf8Coder.getEncodedElementByteSize(StringUtf8Coder.java:37)
at org.apache.beam.sdk.coders.Coder.registerByteSizeObserver(Coder.java:291)
at com.spotify.scio.coders.RecordCoder.registerByteSizeObserver(Coder.scala:279)
at org.apache.beam.sdk.util.WindowedValue$FullWindowedValueCoder.registerByteSizeObserver(WindowedValue.java:564)
at org.apache.beam.sdk.util.WindowedValue$FullWindowedValueCoder.registerByteSizeObserver(WindowedValue.java:480)
at org.apache.beam.runners.dataflow.worker.IntrinsicMapTaskExecutorFactory$ElementByteSizeObservableCoder.registerByteSizeObserver(IntrinsicMapTaskExecutorFactory.java:399)
at org.apache.beam.runners.dataflow.worker.util.common.worker.OutputObjectAndByteCounter.update(OutputObjectAndByteCounter.java:125)
at org.apache.beam.runners.dataflow.worker.DataflowOutputCounter.update(DataflowOutputCounter.java:64)
at org.apache.beam.runners.dataflow.worker.util.common.worker.OutputReceiver.process(OutputReceiver.java:43)
at org.apache.beam.runners.dataflow.worker.SimpleParDoFn$1.output(SimpleParDoFn.java:272)
at org.apache.beam.runners.core.SimpleDoFnRunner.outputWindowedValue(SimpleDoFnRunner.java:309)
at org.apache.beam.runners.core.SimpleDoFnRunner.access$700(SimpleDoFnRunner.java:77)
at org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:621)
at org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:609)
at com.spotify.scio.util.Functions$$anon$3.processElement(Functions.scala:158)
at com.spotify.scio.util.Functions$$anon$3$DoFnInvoker.invokeProcessElement(Unknown Source)
at org.apache.beam.runners.core.SimpleDoFnRunner.invokeProcessElement(SimpleDoFnRunner.java:275)
at org.apache.beam.runners.core.SimpleDoFnRunner.processElement(SimpleDoFnRunner.java:240)
at org.apache.beam.runners.dataflow.worker.SimpleParDoFn.processElement(SimpleParDoFn.java:325)
at org.apache.beam.runners.dataflow.worker.util.common.worker.ParDoOperation.process(ParDoOperation.java:44)
at org.apache.beam.runners.dataflow.worker.util.common.worker.OutputReceiver.process(OutputReceiver.java:49)
at org.apache.beam.runners.dataflow.worker.util.common.worker.ReadOperation.runReadLoop(ReadOperation.java:201)
at org.apache.beam.runners.dataflow.worker.util.common.worker.ReadOperation.start(ReadOperation.java:159)
at org.apache.beam.runners.dataflow.worker.util.common.worker.MapTaskExecutor.execute(MapTaskExecutor.java:76)
at org.apache.beam.runners.dataflow.worker.BatchDataflowWorker.executeWork(BatchDataflowWorker.java:394)
at org.apache.beam.runners.dataflow.worker.BatchDataflowWorker.doWork(BatchDataflowWorker.java:363)
at org.apache.beam.runners.dataflow.worker.BatchDataflowWorker.getAndPerformWork(BatchDataflowWorker.java:291)
at org.apache.beam.runners.dataflow.worker.DataflowBatchWorkerHarness$WorkerThread.doWork(DataflowBatchWorkerHarness.java:135)
at org.apache.beam.runners.dataflow.worker.DataflowBatchWorkerHarness$WorkerThread.call(DataflowBatchWorkerHarness.java:115)
at org.apache.beam.runners.dataflow.worker.DataflowBatchWorkerHarness$WorkerThread.call(DataflowBatchWorkerHarness.java:102)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
我猜我的输入文件之一可能包含一些格式错误的数据。但是如何绕过不良数据呢？ Java Beam com.google.cloud.dataflow.sdk.coders.CoderException: cannot encode a null String也有类似的问题 所以我尝试了这个：
val scText = sc.textFile(input)
scText.setCoder(NullableCoder.of(StringUtf8Coder.of()))
它没有帮助。有人可以帮我吗？谢谢。