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https://issues.apache.org/jira/browse/FLINK-9694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16539966#comment-16539966
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ASF GitHub Bot commented on FLINK-9694:
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Github user zentol commented on the issue:
https://github.com/apache/flink/pull/6231
This doesn't look correct to me, the serializer should always be non-null,
and silently dropping null serializers most likely just causes other problems.
Did you actually run into this NPE when using Flink, or did you explicitly
call the constructor for demonstration purposes?
As far as I can tell the code in `CRowSerializer` is either broken or a not
adequately documented hack.
It is at the very least untested as this NPE _always_ occur when this
constructor is used.
@tzulitai Why exactly is this
[constructor](https://github.com/apache/flink/blob/master/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/types/CRowSerializer.scala#L123)
necessary?
> Potentially NPE in CompositeTypeSerializerConfigSnapshot constructor
> --------------------------------------------------------------------
>
> Key: FLINK-9694
> URL: https://issues.apache.org/jira/browse/FLINK-9694
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Affects Versions: 1.5.0
> Reporter: vinoyang
> Assignee: vinoyang
> Priority: Minor
> Labels: pull-request-available
>
> the partial specific exception stack trace :
> {code:java}
> Caused by: java.lang.NullPointerException
> at
> org.apache.flink.api.common.typeutils.CompositeTypeSerializerConfigSnapshot.<init>(CompositeTypeSerializerConfigSnapshot.java:53)
> at
> org.apache.flink.table.runtime.types.CRowSerializer$CRowSerializerConfigSnapshot.<init>(CRowSerializer.scala:120)
> at
> org.apache.flink.table.runtime.types.CRowSerializer$CRowSerializerConfigSnapshot.<init>(CRowSerializer.scala:123)
> at sun.reflect.GeneratedConstructorAccessor10.newInstance(Unknown Source)
> at
> sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
> at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
> at java.lang.Class.newInstance(Class.java:442)
> at
> org.apache.flink.util.InstantiationUtil.instantiate(InstantiationUtil.java:319)
> ... 20 more{code}
> related code is :
> {code:java}
> public CompositeTypeSerializerConfigSnapshot(TypeSerializer<?>...
> nestedSerializers) {
> Preconditions.checkNotNull(nestedSerializers);
> this.nestedSerializersAndConfigs = new
> ArrayList<>(nestedSerializers.length);
> for (TypeSerializer<?> nestedSerializer : nestedSerializers) {
> TypeSerializerConfigSnapshot configSnapshot =
> nestedSerializer.snapshotConfiguration();
> this.nestedSerializersAndConfigs.add(
> new Tuple2<TypeSerializer<?>, TypeSerializerConfigSnapshot>(
> nestedSerializer.duplicate(),
> Preconditions.checkNotNull(configSnapshot)));
> }
> }
> {code}
> exception happens at :
> {code:java}
> TypeSerializerConfigSnapshot configSnapshot =
> nestedSerializer.snapshotConfiguration();
> {code}
> the reason is the type of constructor's parameter "..." used "varargs"
> feature. The initialize code in *CRowSerializer.scala* is :
> {code:java}
> def this() = this(null) // Scala code
> {code}
> when invoked this, actually the the type of
> CompositeTypeSerializerConfigSnapshot's
> nestedSerializers parameter is :
> {code:java}
> TypeSerializer<?>[] nestedSerializers = new TypeSerializer<?>[] {null};
> {code}
> so the checkNotNull precondition statement :
> {code:java}
> Preconditions.checkNotNull(nestedSerializers);
> {code}
> is always useless.
> So we should check the object reference in _for_ loop to protect NPE.
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