[java][microprofile] Extend support for useOneOfInterfaces to the microprofile library when Jackson serialisation is enabled

[Ignacio-Vidal]

[java][microprofile] Support useOneOfInterfaces

The java client generator already supports oneOfInterface templating and it's currently used by the Spring library variants. This PR extends this to the Microprofile library when Jackson is selected for serialisation.

It renders a oneOf schema as a Java interface (implemented by its subtypes) for the microprofile library, instead of an unrelated pojo.

The microprofile library ships its own model.mustache and supports serializationLibrary=jackson and serialisationLibrary=jsonB. This PR guarantees support Jackson and JsonB will be verified in a follow up PR.

Add support for OneOfInterfaces to avoid having circular dependencies because the child schemas components extend a parent class that also has oneOf and mapping pointing to the children. Example:

   # -----------------------------------------------
   # Base schema in component that contains oneOf and mapping
   # Discriminator also lives here on the parent
   # Child classes have a circular dependency because allOf to the parent with the oneOf & mapping
   # PetRequest (mapping) -> CatRequest (allOf) -> PetRequest
   # -----------------------------------------------

   PetRequest:
     type: object
     required:
       - petType
       - name
     properties:
       petType:
         type: string
         enum:
           - CAT
           - DOG
       name:
         type: string
     discriminator:
       propertyName: petType
       mapping:
         CAT: '#/components/schemas/CatRequest'
         DOG: '#/components/schemas/DogRequest'

   CatRequest:
     type: object
     allOf:
       - $ref: '#/components/schemas/PetRequest'
       - type: object
         required:
           - breedType
           - petType
         properties:
           breedType:
             $ref: '#/components/schemas/CatBreedType'
   DogRequest:
     type: object
     allOf:
       - $ref: '#/components/schemas/PetRequest'
       - type: object
         properties:
           breedType:
             $ref: '#/components/schemas/DogBreedType'


   # -----------------------------------------------
   # Base schema a separate component
   # Discriminator lives in parent and base object until #24156 is merged
   # -----------------------------------------------

   PetRequestV2:
     type: object
     properties:
       petType:
         $ref: '#/components/schemas/PetType'      # --> This will removed once #24156 is merged
     oneOf:
       - $ref: '#/components/schemas/CatRequestV2'
       - $ref: '#/components/schemas/DogRequestV2'
     discriminator:
       propertyName: petType
       mapping:
         CAT: '#/components/schemas/CatRequestV2'
         DOG: '#/components/schemas/DogRequestV2'

   PetRequestV2Base:
       type: object
       required:
         - petType
         - name
       properties:
         petType:
           $ref: '#/components/schemas/PetType'
         name:
           type: string
   
   CatRequestV2:
     type: object
     allOf:
       - $ref: '#/components/schemas/PetRequestV2Base'
       - type: object
         properties:
           breedType:
             $ref: '#/components/schemas/CatBreedType'
          

   DogRequestV2:
     type: object
     allOf:
       - $ref: '#/components/schemas/PetRequestV2Base'
       - type: object
         properties:
           breedType:
             $ref: '#/components/schemas/DogBreedType'

---

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---

Summary by cubic

Extends useOneOfInterfaces to the Java MicroProfile client when serializationLibrary=jackson, rendering oneOf schemas as interfaces implemented by subtypes. Adds a MicroProfile sample and CI coverage.

• New Features
  • Route MicroProfile model.mustache to the shared oneof_interface template via vendorExtensions.x-is-one-of-interface when useOneOfInterfaces=true and serializationLibrary=jackson; fall back to pojo otherwise.
  • Added a minimal fixture (modules/openapi-generator/src/test/resources/3_0/java/oneof_interface_petstore.yaml), generator config (bin/configs/java-microprofile-oneof-interface.yaml, MicroProfile Rest Client 3.0), a JavaClientCodegenTest, and a sample at samples/client/petstore/java/microprofile-oneof-interface.
  • The test verifies the oneOf container is an interface, children implement it, the discriminator getter returns the enum type, and interfaces are non-sealed by default.
  • Added the sample to the Java client JDK 11 samples workflow.
  • useSealedOneOfInterfaces is not enabled; jsonb is not supported yet.

^{Written for commit ab33a9c. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found and verified against the latest diff

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[Ignacio-Vidal]

I test these changes in a separate project: https://github.com/Ignacio-Vidal/openapi-servers/tree/main

And these 2 PRs supporting oneOfInterfaces in the server and client generators are covered:

• contract: https://github.com/Ignacio-Vidal/openapi-servers/blob/main/contracts/src/main/resources/META-INF/openapi.yaml#L76
• Server implementation using jaxrs-spec/quarkus generator: https://github.com/Ignacio-Vidal/openapi-servers/blob/main/quarkus-app/src/main/java/com/example/PetAdapter.java#L35
• Tests using java/microprofile client generator : https://github.com/Ignacio-Vidal/openapi-servers/blob/main/quarkus-app/src/test/java/com/example/PetApiTest.java#L132

I create a branch that combined #24190 and #24174 in my local and installed into my m2 repository

[wing328]

please add the new output folder to the gihtub workflow for java client in https://github.com/OpenAPITools/openapi-generator/blob/master/.github/workflows/samples-java-client-jdk11.yaml

[Ignacio-Vidal]

done