Hi, Team, I am trying to write a custom aggregate function (extending the

AggregateFunction

class)using Table API to group by a set of columns and collect an Array of String in the aggregate function. When the group window emitter tries to emit the result of the aggregation, am getting a class cast exception.

java.lang.ClassCastException: class java.lang.String cannot be cast to class [Ljava.lang.Object; (java.lang.String and [Ljava.lang.Object; are in module java.base of loader 'bootstrap')
	at org.apache.flink.table.data.conversion.ArrayObjectArrayConverter.toInternal(ArrayObjectArrayConverter.java:40)
	at org.apache.flink.table.data.conversion.DataStructureConverter.toInternalOrNull(DataStructureConverter.java:61)
	at org.apache.flink.table.data.conversion.RowRowConverter.toInternal(RowRowConverter.java:75)
	at org.apache.flink.table.data.conversion.RowRowConverter.toInternal(RowRowConverter.java:37)
	at org.apache.flink.table.data.conversion.DataStructureConverter.toInternalOrNull(DataStructureConverter.java:61)
	at GroupingWindowAggsHandler$173.getValue(Unknown Source)
	at org.apache.flink.table.runtime.operators.window.AggregateWindowOperator.emitWindowResult(AggregateWindowOperator.java:164)
	at org.apache.flink.table.runtime.operators.window.WindowOperator.onEventTime(WindowOperator.java:390)
	at org.apache.flink.streaming.api.operators.InternalTimerServiceImpl.advanceWatermark(InternalTimerServiceImpl.java:302)
	at org.apache.flink.streaming.api.operators.InternalTimeServiceManagerImpl.advanceWatermark(InternalTimeServiceManagerImpl.java:180)
	at org.apache.flink.streaming.api.operators.AbstractStreamOperator.processWatermark(AbstractStreamOperator.java:599)
	at org.apache.flink.streaming.runtime.tasks.OneInputStreamTask$StreamTaskNetworkOutput.emitWatermark(OneInputStreamTask.java:239)
	at org.apache.flink.streaming.runtime.watermarkstatus.StatusWatermarkValve.findAndOutputNewMinWatermarkAcrossAlignedChannels(StatusWatermarkValve.java:200)
	at org.apache.flink.streaming.runtime.watermarkstatus.StatusWatermarkValve.inputWatermark(StatusWatermarkValve.java:105)
	at org.apache.flink.streaming.runtime.io.AbstractStreamTaskNetworkInput.processElement(AbstractStreamTaskNetworkInput.java:136)
	at org.apache.flink.streaming.runtime.io.AbstractStreamTaskNetworkInput.emitNext(AbstractStreamTaskNetworkInput.java:105)
	at org.apache.flink.streaming.runtime.io.StreamOneInputProcessor.processInput(StreamOneInputProcessor.java:65)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.processInput(StreamTask.java:542)
	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMailboxLoop(MailboxProcessor.java:231)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.runMailboxLoop(StreamTask.java:831)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:780)
	at org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:935)
	at org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:914)
	at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:728)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:550)
	at java.base/java.lang.Thread.run(Unknown Source)

The output of the aggregate is a

Row

object with an

Array<String>

elements. Any pointers to what I might be doing wrong? Thanks.