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https://issues.apache.org/jira/browse/FLINK-9694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16553026#comment-16553026
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ASF GitHub Bot commented on FLINK-9694:
---------------------------------------

Github user yanghua commented on the issue:

    https://github.com/apache/flink/pull/6231
  
    @pnowojski thanks for giving a solution, I will try to verify it in our 
inner Flink version.


> 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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