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https://issues.apache.org/jira/browse/AVRO-2918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17738989#comment-17738989
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Samael Bate commented on AVRO-2918:
-----------------------------------
I'd very much like Avro to support this. As a bit of a workaround I've had some
luck using
{{id "io.github.tunguski.interfacer" version "0.0.7"}} in my gradle build along
with the avro gradle-plugin. interfacer allows me to post-process my generated
Java sources and add Interfaces to classes that have been generated by avro
types.
{code:java}
// The interfacer plugin allows us to post-process the generated Java source
and apply interfaces defined in the src folder
tasks.register("avroInterfacer", pl.matsuo.interfacer.gradle.InterfacerTask) {
dependsOn generate
interfacePackage = 'com.domain.schema.core'
interfacesDirectory = file('src/main/java')
scanDirectory = file("build/generated/java")
} {code}
on the records I simply annotate them like {{@java-interface("UserAccount")}}
Unfortunately though the interfacer plugin only has one release and is a one
person project. Ideally I'd like it if Avro itself could support something like
this:
{code:java}
@interface("pubnub.core.PubNubMessage") // this interface can be defined
elsewhere by me
record PubNubPayloadMessage {
union {
null,
CustomerMessagePayload,
SupportStaffL1Payload,
SupportStaffL2Payload
} payload = null;
pubnub.core.PubNubMetadata metadata;
} {code}
where each of those payload records are annotated with
@interface("pubnub.core.PubNubPayload").
today, if I call {{getPayload()}} the return type is _Object_ but with this
approach it would be _PubNubPayload_
> Schema polymorphism
> -------------------
>
> Key: AVRO-2918
> URL: https://issues.apache.org/jira/browse/AVRO-2918
> Project: Apache Avro
> Issue Type: New Feature
> Components: logical types, misc, spec
> Reporter: Jonathan Rapoport
> Assignee: Christophe Le Saec
> Priority: Critical
> Labels: features, pull-request-available
> Original Estimate: 96h
> Time Spent: 10m
> Remaining Estimate: 95h 50m
>
> Include the option to use named types as base types for a new schema. Allow
> for MRO generation. Field inheritance.
> The benefits of this approach include:
> * Defining a schema as validation for a certain wire, and so allowing the
> receiver to be certain of the structure of the data (this works today).
> However, defining an extension of this schema, or certain schemas which can
> be normalized to the original schema, but contain additional information,
> will not allow it to be sent over the same wire.
> * Backwards compatibility through inheritance - you never break the old
> schema, thus allowing a long integration period, with no need to recode all
> processes familiar with the schema. The new schema will simply inherit the
> old one, and only add information.
> * Allow for full data control through polymorphism, and the ability to
> replace structures within any supported language.
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