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https://issues.apache.org/jira/browse/AVRO-2702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17038641#comment-17038641
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Billy Atkins commented on AVRO-2702:
------------------------------------
This issue appears to be caused by commit ea61af8. The logic of the
ResolvingGrammarGenerator.generate method has an optimization to bypass deep
resolution if the union is "equivalent". The logic that sets
WriterUnion.unionEquiv does not interrogate the schema's props. The root issue
is the writer's schema is being used instead of the reader's schema so the
reader's props are not available when deserializing.
[https://github.com/apache/avro/commit/ea61af812478af7e6922b83e0818bf06b91c0052#diff-5985fb2a9bcec5b4a5f9585e2e873395]
Line 106 should be be changed from:
{code:java}
104 } else if (action.writer.getType() == Schema.Type.UNION) {
105 if (((Resolver.WriterUnion)action).unionEquiv)
106 return simpleGen(action.writer, seen);
{code}
to:
{code:java}
104 } else if (action.writer.getType() == Schema.Type.UNION) {
105 if (((Resolver.WriterUnion)action).unionEquiv)
106 return simpleGen(action.reader, seen);
{code}
> Avro ResolvingGrammarGenerator does not honor "avro.java.string" property in
> inner record schemas
> -------------------------------------------------------------------------------------------------
>
> Key: AVRO-2702
> URL: https://issues.apache.org/jira/browse/AVRO-2702
> Project: Apache Avro
> Issue Type: Bug
> Components: java
> Affects Versions: 1.9.1
> Reporter: Thorsten Hake
> Priority: Major
> Labels: ClassCastException, Deserialize
> Attachments: Bar.kt
>
>
> The type property "avro.java.string" is being used to qualify the
> CharSequence implementation of a string type in java. This property will be
> set in the java code generated by the avro maven plugin, if the <stringType>
> property is set to "String".
> However the ResolvingGrammarGenerator, which helps in matching the writer
> schema to the reader schema, does not honor this property for inner records
> within unions. Instead of deserializing to java.lang.String, the strings of
> the inner record will be deserialized to org.apache.avro.util.Utf8. String
> properties belonging to the outer record will be correctly deserialized to
> java.lang.String.
> If you try to deserialize an Avro record from a schema that has an inner
> record within an union type with the java code generated by the maven plugin
> (<stringType> is set to "String"), you'll get a ClassCastException:
> {noformat}
> Caused by: java.lang.ClassCastException: class org.apache.avro.util.Utf8
> cannot be cast to class java.lang.String
> {noformat}
> This is because the generated java code expects the strings to be
> deserialized according to the "avro.java.string" property which does not
> happen for the inner record.
> I would expect that the deserializer treats the strings in the inner record
> the same as the strings in the outer record.
> Example:
> writer schema:
> {code:json}
> {
> "type": "record",
> "name": "foo",
> "fields": [
> {
> "name": "k",
> "type": "string"
> },
> {
> "name": "value",
> "type": [
> "null",
> {
> "type": "record",
> "name": "bar",
> "fields": [
> {
> "name": "str",
> "type": "string"
> }
> ]
> }
> ]
> }
> ]
> }
> {code}
> reader schema:
> {code:json}
> {
> "type": "record",
> "name": "foo",
> "fields": [
> {
> "name": "k",
> "type": {
> "type": "string",
> "avro.java.string": "String"
> }
> },
> {
> "name": "value",
> "type": [
> "null",
> {
> "type": "record",
> "name": "bar",
> "fields": [
> {
> "name": "str",
> "type": {
> "type": "string",
> "avro.java.string": "String"
> }
> }
> ]
> }
> ]
> }
> ]
> }
> {code}
> You'll find some example kotlin code demonstrating the problem in the
> attached Bar.kt.
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