[BUG] [JAVA] Generated @JsonTypeName conflicts with value of x-discriminator-value when ModelNameSuffix is used

[jpfinne]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

[BUG] [JAVA] Generated @JsonTypeName doesn't use the value of x-discriminator-value.
Jackson created incorrect json

Description

x-discriminator-value is the only way to customize the value of the discriminator in swagger 2.
Since 7.1.0 it is not taken into account anymore when modelNameSuffix is used.
The name of the element is always used.
It gives a huge regression in the json processing.

The parent contains the correct mapping:

@JsonSubTypes({
  @JsonSubTypes.Type(value = CatItemDto.class, name = "CAT"),
  @JsonSubTypes.Type(value = DogItemDto.class, name = "DOG")
})

But it is superseeded in the child classes

@JsonTypeName("DogItem")
public class DogItemDto extends PetItemDto {

Expected:

no @JsonTypeName annotation
if you remove @JsonTypeName from template everything works fine (Jackson seems to retrieve typeName from parent).

public class DogItemDTO extends PetItemDTO {

alternatively @JsonTypeName("DOG") is also valid

@JsonTypeName("DOG") 
public class DogItemDTO extends PetItemDTO {

So that Jackson creates this json
{"type":"DOG","identifier":"Medor","packSize":10}

Actual in 7.1.0 and 7.2.0

@JsonTypeName("DogItem")
public class DogItemApiDTO extends PetItemApiDTO {

Jackson generates
{"type":"DogItem","identifier":"Medor","packSize":10}

This json can not be unmarshalled by application using a different version of the generator. In my case typescript-angular fails to unmarshall

openapi-generator version 7.1.0

regression since 6.4.0. Maybe fix for #14731

OpenAPI declaration file content or url

swagger: "2.0"
info:
  version: 1.0.0
  title: x-discriminator-value bug
paths:
  /getItems:
    get:
      description: test
      operationId: getAllPets
      responses:
        200:
          description: 'list of PetItems'
          schema:
            type: array
            items:
              $ref: '#/definitions/PetItem'
definitions:
  PetType:
    type: string
    enum:
      - DOG
      - CAT
  PetItem:
    discriminator: type
    properties:
      identifier:
        type: string
      type:
        $ref: '#/definitions/PetType'

  DogItem:
    x-discriminator-value: DOG
    allOf:
      - $ref: '#/definitions/PetItem'
      - type: object
        properties:
          packSize:
            type: integer
  CatItem:
    x-discriminator-value: CAT
    allOf:
      - $ref: '#/definitions/PetItem'
      - type: object
        properties:
          huntingSkill:
            type: string

Generation Details

openapi-generator-cli generate -i swaggerDiscriminator.yaml -g spring --model-name-suffix=Dto

Steps to reproduce

Contract in swagger-2
inheritance with a discriminator
use of x-discriminator-value
modelNameSuffix

Use the spring generator.

Related issues/PRs

#10822

Suggest a fix

Update pojo.mustache to use the vendorExtensions.x-discriminator-value if it exists

{{^hasDiscriminatorWithNonEmptyMapping}}
@JsonTypeName("{{^vendorExtensions.x-discriminator-value}}{{name}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{vendorExtensions.x-discriminator-value}}{{/vendorExtensions.x-discriminator-value}}")
{{/hasDiscriminatorWithNonEmptyMapping}}

[jroch]

Same issue here.

[dragutint]

Same issue here, 7.7.0 version.
jaxrs-spec server generator, with and without ModelNameSuffix. With java generator and native library it generates a class without @JsonTypeName annotation and with @JsonIgnoreProperties annotations, and (de)serialization works fine this way.

If possible, I would like to contribute to fixing this issue.

[pboos]

Is there a workaround for this?

@jpfinne I saw your very promising PR: #17781
What is the reason that it got closed? Would have been great to get that one in as it would have solved this issue.

[vicinzu]

Same issue here. Version: 7.9.0

My temporary workaround is to add a mix-in to the object mapper with the correct annotation, e.g.

configure min-ins

objectMapper.addMixIn(CatItemDto.class, CatItemDtoMinIn.class);
objectMapper.addMixIn(DogItemDto.class, DogItemDtoMinIn.class);

CatItemDtoMinIn

@JsonTypeName("CAT")
public abstract class CatItemDtoMinIn {

}

DogItemDtoMinIn

@JsonTypeName("DOG")
public abstract class DogItemDtoMinIn {

}

[mvazquezrius]

Same issue in 7.12.0

@jpfinne @wing328 why was the PR closed? And is there a way we can get this bug fixed?

[Ignacio-Vidal]

This is happening with jaxrs-spec in version 7.19.0, any chance this could be fixed? It doesn't respect the x-discriminator-value and the JsonTypeName annotation is incorrectly using the class name instead of the discriminator value, resulting in serialisation issues

 configOptions.set(
        mapOf(
            "bigDecimalAsString" to "true",
            "dateLibrary" to "java8",
            "disallowAdditionalPropertiesIfNotPresent" to "false",
            "discriminatorCaseSensitive" to "true",
            "generateConstructorWithAllArgs" to "true",
            "implicitHeaders" to "true",
            "interfaceOnly" to "true",
            "legacyDiscriminatorBehavior" to "false",
            "library" to "quarkus",
            "openApiNullable" to "false",
            "returnResponse" to "false",
            "serializableModel" to "false",
            "useBeanValidation" to "true",
            "useJakartaEe" to "true",
            "useMicroProfileOpenAPIAnnotations" to "true",
            "useSwaggerAnnotations" to "false",
            "useTags" to "true"
        )
    )

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "petType", visible = true)
@JsonSubTypes({
})
/**
 * Request payload for creating a dog
 **/

@org.eclipse.microprofile.openapi.annotations.media.Schema(description="Request payload for creating a dog")
@JsonTypeName("DogRequest") // INCORRECT ---> SHOULD BE @JsonTypeName("DOG")
@jakarta.annotation.Generated(value = "org.openapitools.codegen.languages.JavaJAXRSSpecServerCodegen", date = "2026-02-15T20:51:30.585223Z[Europe/London]")
public class DogRequest extends PetRequest  {
  private @Valid DogBreedType breedType;
  private @Valid Boolean trained;
  private @Valid Double weightKg;

and the superType:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "petType", visible = true)
@JsonSubTypes({
  @JsonSubTypes.Type(value = CatRequest.class, name = "CAT"),
  @JsonSubTypes.Type(value = DogRequest.class, name = "DOG"),
})


@org.eclipse.microprofile.openapi.annotations.media.Schema(description="")
@JsonTypeName("PetRequest")
@jakarta.annotation.Generated(value = "org.openapitools.codegen.languages.JavaJAXRSSpecServerCodegen", date = "2026-02-15T20:51:30.585223Z[Europe/London]")
public class PetRequest   {
  private @Valid PetType petType;
  private @Valid String name;

See this openapi definition to test it:

openapi: "3.1.1"
info:
  title: Pet API
  version: "1.0.0"
  description: API for creating pets supporting cats and dogs

paths:
  /pets:
    post:
      summary: Create a pet
      operationId: createPet
      tags:
        - Pets
      requestBody:
        required: true
        content:
          application/json:
            schema:
              title: PetRequest
              $ref: "#/components/schemas/PetRequest"
            examples:
              cat:
                summary: Cat request
                value:
                  petType: CAT
                  name: "Whiskers"
                  indoor: true
                  breedType: DOMESTIC_SHORTHAIR
              dog:
                summary: Dog request
                value:
                  petType: DOG
                  name: "Buddy"
                  breedType: LABRADOR
                  trained: true
      responses:
        '201':
          description: Pet created successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/PetResponse'
              examples:
                cat:
                  summary: Cat response
                  value:
                    id: "pet_01HQ7CAT123456789"
                    petType: CAT
                    name: "Whiskers"
                    indoor: true
                    breedType: DOMESTIC_SHORTHAIR
                    createdAt: "2024-02-01T10:30:00Z"
                dog:
                  summary: Dog response
                  value:
                    id: "pet_01HQ7DOG987654321"
                    petType: DOG
                    name: "Buddy"
                    breedType: LABRADOR
                    trained: true
                    createdAt: "2024-02-01T10:30:00Z"

components:
  schemas:

    # -----------------------------------------------
    # Shared enum
    # -----------------------------------------------

    PetType:
      type: string
      enum:
        - CAT
        - DOG
      description: Discriminator field identifying the type of pet

    CatBreedType:
      type: string
      enum:
        - DOMESTIC_SHORTHAIR
        - PERSIAN
        - MAINE_COON
        - SIAMESE
        - BENGAL
      description: Breed of the cat

    DogBreedType:
      type: string
      enum:
        - LABRADOR
        - GOLDEN_RETRIEVER
        - BULLDOG
        - POODLE
        - GERMAN_SHEPHERD
      description: Breed of the dog

    # -----------------------------------------------
    # Request base schema
    # Discriminator lives here on the parent so the
    # openapi generator produces correct Java
    # inheritance with extends rather than flattening
    # -----------------------------------------------

    PetRequest:
      type: object
      required:
        - petType
        - name
      properties:
        petType:
          $ref: '#/components/schemas/PetType'
        name:
          type: string
          minLength: 1
          maxLength: 50
          description: Name of the pet
          examples:
            - "Whiskers"
      discriminator:
        propertyName: petType
        mapping:
          CAT: '#/components/schemas/CatRequest'
          DOG: '#/components/schemas/DogRequest'

    # -----------------------------------------------
    # Response base schema
    # Discriminator also lives here on the parent
    # -----------------------------------------------

    PetResponse:
      type: object
      required:
        - petType
      properties:
        petType:
          $ref: '#/components/schemas/PetType'
        name:
          type: string
          minLength: 1
          maxLength: 50
          description: Name of the pet
          examples:
            - "Whiskers"
      discriminator:
        propertyName: petType
        mapping:
          CAT: '#/components/schemas/CatResponse'
          DOG: '#/components/schemas/DogResponse'

    # -----------------------------------------------
    # Cat request - child references parent via allOf
    # -----------------------------------------------

    CatRequest:
      type: object
      x-discriminator-value: CAT   # <- controls generated @JsonTypeName / discriminator value
      description: Request payload for creating a cat
      allOf:
        - $ref: '#/components/schemas/PetRequest'
        - type: object
          required:
            - breedType
            - indoor
          properties:
            breedType:
              $ref: '#/components/schemas/CatBreedType'
            indoor:
              type: boolean
              description: Whether the cat is an indoor cat
              examples:
                - true
            declawed:
              type: boolean
              description: Whether the cat has been declawed
              examples:
                - false

    # -----------------------------------------------
    # Dog request - child references parent via allOf
    # -----------------------------------------------

    DogRequest:
      type: object
      x-discriminator-value: DOG
      description: Request payload for creating a dog
      allOf:
        - $ref: '#/components/schemas/PetRequest'
        - type: object
          required:
            - breedType
            - trained
          properties:
            breedType:
              $ref: '#/components/schemas/DogBreedType'
            trained:
              type: boolean
              description: Whether the dog is house trained
              examples:
                - true
            weightKg:
              type: number
              format: double
              minimum: 0.1
              maximum: 120.0
              description: Weight of the dog in kilograms
              examples:
                - 30.5

    # -----------------------------------------------
    # Cat response - child references parent via allOf
    # -----------------------------------------------

    CatResponse:
      type: object
      x-discriminator-value: CAT
      description: Response payload for a cat resource
      allOf:
        - $ref: '#/components/schemas/PetResponse'
        - type: object
          required:
            - breedType
            - indoor
          properties:
            breedType:
              $ref: '#/components/schemas/CatBreedType'
            indoor:
              type: boolean
              description: Whether the cat is an indoor cat
              examples:
                - true
            declawed:
              type: boolean
              description: Whether the cat has been declawed
              examples:
                - false

    # -----------------------------------------------
    # Dog response - child references parent via allOf
    # -----------------------------------------------

    DogResponse:
      type: object
      x-discriminator-value: DOG
      description: Response payload for a dog resource
      allOf:
        - $ref: '#/components/schemas/PetResponse'
        - type: object
          required:
            - breedType
            - trained
          properties:
            breedType:
              $ref: '#/components/schemas/DogBreedType'
            trained:
              type: boolean
              description: Whether the dog is house trained
              examples:
                - true
            weightKg:
              type: number
              format: double
              minimum: 0.1
              maximum: 120.0
              description: Weight of the dog in kilograms
              examples:
                - 30.5