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https://issues.apache.org/jira/browse/FLINK-2809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14943277#comment-14943277
]
ASF GitHub Bot commented on FLINK-2809:
---------------------------------------
Github user ggevay commented on a diff in the pull request:
https://github.com/apache/flink/pull/1217#discussion_r41135832
--- Diff:
flink-java/src/main/java/org/apache/flink/api/java/io/CollectionInputFormat.java
---
@@ -130,8 +130,14 @@ public String toString() {
if (elem == null) {
throw new IllegalArgumentException("The
collection must not contain null elements.");
}
-
- if (!viewedAs.isAssignableFrom(elem.getClass())) {
+
+ // The second part of the condition is a workaround for
the situation that can arise from eg.
+ // "env.fromElements((),(),())"
+ // In this situation, UnitTypeInfo.getTypeClass returns
void.class (when we are in the Java world), but
+ // the actual objects that we will be working with,
will be BoxedUnits.
+ if (!viewedAs.isAssignableFrom(elem.getClass()) &&
--- End diff --
I agree that this is not elegant, but I don't see any better way.
UnitTypeInfo.getTypeClass can't return classOf[BoxedUnit], because
TypeInformation<T>.getTypeClass() returns Class<T>, and here T is Unit.
I already had a test for this in TypeInformationGenTest.testUnit. Now I
also added a comment, that explains that those two lines in the test are
testing this condition.
By the way, if you really dislike this condition, then I can just remove
it. The rest of the PR already solves my original problem, so I can live
without "fromElements((),(),())" working.
> DataSet[Unit] doesn't work
> --------------------------
>
> Key: FLINK-2809
> URL: https://issues.apache.org/jira/browse/FLINK-2809
> Project: Flink
> Issue Type: Bug
> Components: Scala API
> Reporter: Gabor Gevay
> Assignee: Gabor Gevay
> Priority: Minor
>
> The following code creates a DataSet\[Unit\]:
> val env = ExecutionEnvironment.createLocalEnvironment()
> val a = env.fromElements(1,2,3)
> val b = a.map (_ => ())
> b.writeAsText("/tmp/xxx")
> env.execute()
> This doesn't work, because a VoidSerializer is created, which can't cope with
> a BoxedUnit. See exception below.
> I'm now thinking about creating a UnitSerializer class.
> org.apache.flink.runtime.client.JobExecutionException: Job execution failed.
> at
> org.apache.flink.runtime.jobmanager.JobManager$$anonfun$receiveWithLogMessages$1.applyOrElse(JobManager.scala:314)
> at
> scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:36)
> at
> org.apache.flink.runtime.ActorLogMessages$$anon$1.apply(ActorLogMessages.scala:36)
> at
> org.apache.flink.runtime.ActorLogMessages$$anon$1.apply(ActorLogMessages.scala:29)
> at scala.PartialFunction$class.applyOrElse(PartialFunction.scala:123)
> at
> org.apache.flink.runtime.ActorLogMessages$$anon$1.applyOrElse(ActorLogMessages.scala:29)
> at akka.actor.Actor$class.aroundReceive(Actor.scala:465)
> at
> org.apache.flink.runtime.jobmanager.JobManager.aroundReceive(JobManager.scala:92)
> at akka.actor.ActorCell.receiveMessage(ActorCell.scala:516)
> at akka.actor.ActorCell.invoke(ActorCell.scala:487)
> at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:254)
> at akka.dispatch.Mailbox.run(Mailbox.scala:221)
> at akka.dispatch.Mailbox.exec(Mailbox.scala:231)
> at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
> at
> scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
> at
> scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
> at
> scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
> Caused by: java.lang.ClassCastException: scala.runtime.BoxedUnit cannot be
> cast to java.lang.Void
> at
> org.apache.flink.api.common.typeutils.base.VoidSerializer.serialize(VoidSerializer.java:26)
> at
> org.apache.flink.runtime.plugable.SerializationDelegate.write(SerializationDelegate.java:51)
> at
> org.apache.flink.runtime.io.network.api.serialization.SpanningRecordSerializer.addRecord(SpanningRecordSerializer.java:76)
> at
> org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:83)
> at
> org.apache.flink.runtime.operators.shipping.OutputCollector.collect(OutputCollector.java:65)
> at
> org.apache.flink.runtime.operators.chaining.ChainedMapDriver.collect(ChainedMapDriver.java:78)
> at
> org.apache.flink.runtime.operators.DataSourceTask.invoke(DataSourceTask.java:177)
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:564)
> at java.lang.Thread.run(Thread.java:745)
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