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https://issues.apache.org/jira/browse/BEAM-6963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17459208#comment-17459208
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Jan Eerdekens commented on BEAM-6963:
-------------------------------------
I'm affected by this problem on GCP Dataflow where runtime options with
defaults don't work correctly and return `null`.
> Bug in RuntimeValueProvider JSON serialization
> ----------------------------------------------
>
> Key: BEAM-6963
> URL: https://issues.apache.org/jira/browse/BEAM-6963
> Project: Beam
> Issue Type: Bug
> Components: sdk-java-core
> Affects Versions: 2.11.0
> Reporter: Balázs Németh
> Priority: P3
> Labels: Clarified
> Time Spent: 20m
> Remaining Estimate: 0h
>
> Classes affected:
> org.apache.beam.sdk.options.ValueProvider.Serializer
> org.apache.beam.sdk.options.ValueProvider.Deserializer
> The problem is that according to the JsonDeserializer documentation, the
> deserialize method isn't executed for null nodes:
> (
> [https://static.javadoc.io/com.fasterxml.jackson.core/jackson-databind/2.9.6/com/fasterxml/jackson/databind/JsonDeserializer.html#deserialize(com.fasterxml.jackson.core.JsonParser,%20com.fasterxml.jackson.databind.DeserializationContext)|https://static.javadoc.io/com.fasterxml.jackson.core/jackson-databind/2.9.6/com/fasterxml/jackson/databind/JsonDeserializer.html#deserialize(com.fasterxml.jackson.core.JsonParser,%20com.fasterxml.jackson.databind.DeserializationContext]
> )
> )
> "Note that this method is never called for JSON null literal, and thus
> deserializers need (and should) not check for it."
> If we serialize a RuntimeValueProvider, the isAccessible() will return false,
> so we call a writeNull(). During deserialization this isn't handled properly
> as mentioned and our deserialization will return null.
> The end result is that getters with ValueProvider return values will return
> "null". AFAIK ValueProvider getters should be never null.
> My guess is that either we should completely omit serializing
> RuntimeValueProviders, or during deserialization the proper runtime value
> provider should be created again - which requires more than just a simple
> "null" being present in the json.
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