解析JSON时的Google Cloud Dataflow Javascript UDF错误

时间：2019-04-12 08:10:02

标签： javascript google-bigquery google-cloud-dataflow google-cloud-pubsub

我已使用发布/订阅到BigQuery template来流传输发送到发布/订阅主题的JSON数据。通过数据流，我想展平数据以匹配BigQuery模式并对其进行流式处理。

以下是用于数据流过程的Javascript UDF：

function transform(inJson) {
    var obj = JSON.parse(inJson);
    // variable declarations
    // ... 
    data['domain'] = obj['data']['domain']; // line 18
    ...

    return JSON.stringify(data);
}

我也尝试过：

data.domain = obj.data.domain;

我刚刚从here复制了示例，并将其扩展为扁平化JSON数据。

这是错误消息：

TypeError: Cannot read property "domain" from undefined in <eval> at line number 18

和堆栈跟踪：

javax.script.ScriptException: TypeError: Cannot read property "domain" from undefined in <eval> at line number 18
    at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:470)
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:392)
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeFunction(NashornScriptEngine.java:190)
    at com.google.cloud.teleport.templates.common.JavascriptTextTransformer$JavascriptRuntime.invoke(JavascriptTextTransformer.java:156)
    at com.google.cloud.teleport.templates.common.JavascriptTextTransformer$FailsafeJavascriptUdf$1.processElement(JavascriptTextTransformer.java:315)
    at com.google.cloud.teleport.templates.common.JavascriptTextTransformer$FailsafeJavascriptUdf$1$DoFnInvoker.invokeProcessElement(Unknown Source)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.invokeProcessElement(SimpleDoFnRunner.java:275)
    at org.apache.beam.runners.dataflow.worker.repackaged.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.SimpleParDoFn$1.output(SimpleParDoFn.java:272)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.outputWindowedValue(SimpleDoFnRunner.java:309)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.access$700(SimpleDoFnRunner.java:77)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:621)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:609)
    at com.google.cloud.teleport.templates.PubSubToBigQuery$PubsubMessageToFailsafeElementFn.processElement(PubSubToBigQuery.java:412)
    at com.google.cloud.teleport.templates.PubSubToBigQuery$PubsubMessageToFailsafeElementFn$DoFnInvoker.invokeProcessElement(Unknown Source)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.invokeProcessElement(SimpleDoFnRunner.java:275)
    at org.apache.beam.runners.dataflow.worker.repackaged.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.SimpleParDoFn$1.output(SimpleParDoFn.java:272)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.outputWindowedValue(SimpleDoFnRunner.java:309)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.access$700(SimpleDoFnRunner.java:77)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:621)
    at org.apache.beam.sdk.transforms.DoFnOutputReceivers$WindowedContextOutputReceiver.output(DoFnOutputReceivers.java:71)
    at org.apache.beam.sdk.transforms.MapElements$1.processElement(MapElements.java:122)
    at org.apache.beam.sdk.transforms.MapElements$1$DoFnInvoker.invokeProcessElement(Unknown Source)
    at org.apache.beam.runners.dataflow.worker.repackaged.org.apache.beam.runners.core.SimpleDoFnRunner.invokeProcessElement(SimpleDoFnRunner.java:275)
    at org.apache.beam.runners.dataflow.worker.repackaged.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.StreamingDataflowWorker.process(StreamingDataflowWorker.java:1233)
    at org.apache.beam.runners.dataflow.worker.StreamingDataflowWorker.access$1000(StreamingDataflowWorker.java:144)
    at org.apache.beam.runners.dataflow.worker.StreamingDataflowWorker$6.run(StreamingDataflowWorker.java:972)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: <eval>:18 TypeError: Cannot read property "domain" from undefined
    at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:57)
    at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:213)
    at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:185)
    at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:172)
    at jdk.nashorn.internal.runtime.Undefined.get(Undefined.java:157)
    at jdk.nashorn.internal.scripts.Script$Recompilation$1$7667A$\^eval\_.transform(<eval>:18)
    at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:639)
    at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:494)
    at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:393)
    at jdk.nashorn.api.scripting.ScriptObjectMirror.callMember(ScriptObjectMirror.java:199)
    at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:386)
    ... 42 more

当我通过传递一些示例数据在本地尝试Javascript时，它可以按预期运行，没有任何错误。

更新

结果表明，Pub / Sub发送包装在“中的数据，因此我必须从字符串的开头和结尾删除它们。而且，JSON中的每个”都以\进行转义，因此我也必须在其中删除它们以便继续进行而不会出现任何错误。

2 个答案:

答案 0 :(得分：1)

结果表明Pub / Sub发送了包装在"中的数据，因此我不得不从字符串的开头和结尾删除它们。另外，JSON中的每个"都用\进行了转义，因此我也必须删除它们，以便继续进行而没有任何错误。

答案 1 :(得分：0)

您的JavaScript代码似乎有错误。

data['domain'] = obj['data']['domain']; // line 18

引发以下错误

TypeError: Cannot read property "domain" from undefined in <eval> at line number 18

如果未在某个地方重新初始化变量，则可以在发布到Pub / Sub时尝试将JSON放入单行 即

{"name":"Sam","age":21}
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