[
https://issues.apache.org/jira/browse/AVRO-2918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17739660#comment-17739660
]
Christophe Le Saec commented on AVRO-2918:
------------------------------------------
For generated code, i have an issue with static method, as {_}Java enforce
return type compatibility for overridden *static* methods{_}.
This means this code *does not compile*
{code:java}
public class Person {
public static Integer value() { return 2; }
}
public class Employee extends Person {
public static String value() { return "Two"; }
}
{code}
because String is not a subclass of Integer.
So, in code, it's a problem for methods :
{code:java}
public static BinaryMessageEncoder<Person> getEncoder()
public static BinaryMessageEncoder<Person> getDecoder()
public static BinaryMessageDecoder<Person> createDecode(SchemaStore resolver) {
public static Person.Builder newBuilder()
{code}
that has same for Employee.
As a workarround, i can rename this methods:
{code:java}
public static BinaryMessageEncoder<Person> getEncoderPerson()
public static BinaryMessageEncoder<Employee> getEncoderEmployee()
{code}
...
it works, but lead to uncompatible change.
> 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.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
