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https://issues.apache.org/jira/browse/AVRO-4274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18101405#comment-18101405
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Zachary Payne commented on AVRO-4274:
-------------------------------------
[~rskraba] my team is looking to prioritize this contribution back to Avro in
the next couple of months. Are the proposed changes to the output for Java
Generics acceptable?
> Add Support for Java Generics in ReflectData
> --------------------------------------------
>
> Key: AVRO-4274
> URL: https://issues.apache.org/jira/browse/AVRO-4274
> Project: Apache Avro
> Issue Type: New Feature
> Components: java
> Reporter: Zachary Payne
> Assignee: Ryan Skraba
> Priority: Minor
>
> {{ReflectData}} generates schema by inspecting a class via reflection; when a
> field's declared type is a parameterized type or a type variable (e.g. {{T}}
> from a class {{{}Box<T>{}}}), {{ReflectData}} has no way to resolve those
> type variables to their concrete types. The result is either a runtime error
> or a schema that loses the type information entirely.
> My team has created an extended Avro Java library internally, and we've
> produced a working implementation of this approach and have been running it
> in production. Our extension includes single-level generics, multi-level
> nesting, multiple type parameters, sealed class hierarchies, and union fields
> with generic members. We'd like to contribute this extension of Avro back to
> the open source code.
> All changes are additive. Existing non-generic classes follow the same code
> paths as today.
> *Current Results:* (requires a concrete class {{{}HierarchyAString{}}})
> {code:java}
> {
> "type" : "record",
> "name" : "PojoWithGenericWithString",
> "namespace" : "org.apache.avro.reflect.TestReflect",
> "fields" : [ {
> "name" : "myHierarchyA",
> "type" : {
> "type" : "record",
> "name" : "HierarchyAString",
> "fields" : [ {
> "name" : "value",
> "type" : "string"
> } ]
> }
> } ]
> }
> {code}
> *Our Approach:* (supports a generic instead of a concrete class)
> {code:java}
> {
> "type" : "record",
> "name" : "PojoWithGenericWithString",
> "namespace" : "[...].avro.model.sample.PojoGenerics",
> "fields" : [ {
> "name" : "myHierarchyA",
> "type" : {
> "type" : "record",
> "name" : "HierarchyA_LB_String_RB_",
> "fields" : [ {
> "name" : "value",
> "type" : "string"
> } ],
> "className" : "HierarchyA"
> }
> } ]
> }
> {code}
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