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https://issues.apache.org/jira/browse/AVRO-2236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17744229#comment-17744229
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Christophe Le Saec commented on AVRO-2236:
------------------------------------------
The PR follow roughly the supplied zip file.
> Java Avro Default Value restrictions to first union type leaks to usage of
> record types
> ---------------------------------------------------------------------------------------
>
> Key: AVRO-2236
> URL: https://issues.apache.org/jira/browse/AVRO-2236
> Project: Apache Avro
> Issue Type: Bug
> Components: java
> Affects Versions: 1.8.2
> Reporter: Mario Eberhard
> Assignee: Christophe Le Saec
> Priority: Major
> Labels: pull-request-available
> Attachments: avrodefaulttest.zip
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Default values are restricted to being of the same type as the first type in
> a union.
> {code:java}
> {
> "type": "record",
> "name": "ComplexValue",
> "fields":
> [
> {
> "name": "value",
> "type":
> [
> "null",
> "long"
> ],
> "default": null
> }
> ]
> }
> {code}
> This works as documented. However, the restriction also applies to default
> values of this record type:
> {code:java}
> {
> "type": "record",
> "name": "ExampleRecord",
> "namespace": "com.example",
> "fields":
> [
> {
> "name": "value1",
> "type":
> {
> "type": "record",
> "name": "ComplexValue",
> "fields":
> [
> {
> "name": "value",
> "type":
> [
> "null",
> "long"
> ],
> "default": null
> }
> ]
> }
> },
> {
> "name": "value2",
> "type": "ComplexValue",
> "default":
> {
> "value": 15
> }
> }
> ]
> }
> {code}
> In this case the record "ExampleRecord" has a field "value2" of type
> "ComplexType". This field is not optional but has a default to be able to
> read instance where this field is not present.
> During deserialization the following error is thrown:
> {code:java}
> org.apache.avro.AvroTypeException: Non-null default value for null type: 15
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.encode(ResolvingGrammarGenerator.java:413)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.encode(ResolvingGrammarGenerator.java:365)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.encode(ResolvingGrammarGenerator.java:335)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.getBinary(ResolvingGrammarGenerator.java:307)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.resolveRecords(ResolvingGrammarGenerator.java:285)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.generate(ResolvingGrammarGenerator.java:118)
> at
> org.apache.avro.io.parsing.ResolvingGrammarGenerator.generate(ResolvingGrammarGenerator.java:50)
> at org.apache.avro.io.ResolvingDecoder.resolve(ResolvingDecoder.java:85)
> at org.apache.avro.io.ResolvingDecoder.<init>(ResolvingDecoder.java:49)
> at
> org.apache.avro.io.DecoderFactory.resolvingDecoder(DecoderFactory.java:307)
> at
> org.apache.avro.generic.GenericDatumReader.getResolver(GenericDatumReader.java:128)
> at
> org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:143)
> at
> com.example.SerializationTest.lambda$getDeserializer$1(SerializationTest.java:75)
> at
> com.example.SerializationTest.valueReadWithCorrectDefaultValue(SerializationTest.java:41)
> {code}
> I would argue that a concrete instance of "ComplexValue" with a specific
> value should be allowed in this case. I see no reason why the default
> restriction of the underlying schema should even apply. My guess is, that
> this is an unintended consequence of code reuse in the java client.
> I added an example gradle project as attachment. Run the tests to reproduce
> the above example.
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