[Java] "allOf" does not support inheritance

[vincent-ch]

Description
I just attempted to use allOf in my project to use inheritance in our data model.

openapi-generator version
I am using the Maven plugin: openapi-generator-maven-plugin:4.0.0-beta2

OpenAPI declaration file

UserSpecificService:
  type: object
  required:
    - typ
    - aktiviert
  properties:
    id:
      type: string
      format: int64
    typ:
      $ref: '#/components/schemas/ServiceTyp'
    aktiv:
      type: boolean

PushServiceETA:
  allOf:
    - $ref: '#/components/schemas/UserSpecificService'
    - type: object
      properties:
        verteilerListe:
          type: array
          items:
            $ref: '#/components/schemas/PushVerteilerETA'
        ort:
          $ref: '#/components/schemas/Ort'

Result

public class UserSpecificService {
  private String id;
  private ServiceTyp typ;
  private Boolean aktiv;
}

public class PushServiceETA {
  private String id;
  private ServiceTyp typ;
  private Boolean aktiv;
  private List<PushVerteilerETA> verteilerListe = new ArrayList<>();
  private Ort ort = null;
}

Suggest a fix/enhancement
The Java generator should support single inheritance. It would give us way more flexibilty in the usage of the generated classes in our code.

public class PushServiceETA extends UserSpecificService {
  private List<PushVerteilerETA> verteilerListe = new ArrayList<>();
  private Ort ort = null;
}

[mikhail-putilov]

Technically it is not a bug https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#does-openapi-generator-support-all-new-features-in-openapi-specification-v3

A bug is a mistake in an existing feature. Processing of allOf is simply not there.

[wing328]

@vincent-ch for inheritance, please use discriminator as per OpenAPI spec v3.

Ref: https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#schemaComposition

[vincent-ch]

Thanks for your answer @wing328 , I did a quick test and it looks good. I just have to test how I can configure it with my complexes cases. This is not a bug in this case.

[wing328]

@vincent-ch glad to hear the issue has been resolved for you.

If you like what OpenAPI Generator offers, please consider supporting our voluntary work via https://opencollective.com/openapi_generator

[epabst]

After I got the Pet model working that @marcdejonge provided in #9615 (comment), I figured out a workaround for my own issue. I had separate yaml files for my schema model classes, and by moving them into the same file as the endpoints under this, it worked for me!!!

components:
  schemas: