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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 & 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. -- This message was sent by Atlassian JIRA (v7.6.3#76005)