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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9694) Potentially NPE in CompositeTypeSerializerConfigSnapshot constructor
Date Mon, 23 Jul 2018 14:08:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9694?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16552911#comment-16552911
] 

ASF GitHub Bot commented on FLINK-9694:
---------------------------------------

Github user pnowojski commented on the issue:

    https://github.com/apache/flink/pull/6231
  
    True, `checkNotNull(nestedSerializers);` is useless.
    
    Allowing nulls without enabled compile errors on violated `@Nullable` checks (this we
can not enable in Flink) always leads to some null pointer exceptions and makes developing
code unnecessary complicated - you need to manually walk through whole call stack up and down
to confirm if null can/should be handled/supported/provided. 
    
    This is annoying especially that in 99.9% cases completely avoidable - in this case, just
call different constructor.
    
    I was looking for a way to call this other constructor in Scala and I couldn't (Scala
seems to be annoying), however I found this workaround:
    https://github.com/apache/flink/pull/6392


> 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 &amp; 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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