[BUG][SPRING] Incorrect @JsonTypeName generated for oneOf discriminator mapping regression in 7.23.0

[vmjaws]

Description

After upgrading from OpenAPI Generator 7.12.0 to 7.23.0, the generated Spring models produce inconsistent Jackson polymorphic annotations.

The generated base interface correctly uses the discriminator mapping value:

@JsonSubTypes({
    @JsonSubTypes.Type(
        value = PickupDeliveryRequest.class,
        name = "pickupDelivery"
    )
})

However, the generated subtype is annotated with:

@JsonTypeName("PickupDeliveryRequest")

instead of

@JsonTypeName("pickupDelivery")

Because Jackson serializes using @JsonTypeName, the generated model serializes to:

{
  "requestType": "PickupDeliveryRequest",
  "pickupLocation": "STORE001"
}

instead of the discriminator mapping value:

{

  "requestType": "pickupDelivery",
  "pickupLocation": "STORE001"
}

As a result, the generated models cannot be deserialized correctly by the generated API and Spring returns HttpMessageNotReadableException (400 Bad Request).

Changing the generated annotation manually to

@JsonTypeName("pickupDelivery")

fixes the problem immediately.

This worked correctly with OpenAPI Generator 7.12.0.

openapi-generator version
Working: 7.12.0

Broken: 7.23.0
OpenAPI declaration

openapi: 3.0.3

info:
  title: Discriminator Regression
  version: 1.0.0

paths:
  /delivery:
    put:
      operationId: setDelivery
      requestBody:
        required: true
        content:
          application/json:
            schema:
              oneOf:
                - $ref: '#/components/schemas/PickupDeliveryRequest'
              discriminator:
                propertyName: requestType
                mapping:
                  pickupDelivery: '#/components/schemas/PickupDeliveryRequest'
      responses:
        "204":
          description: OK

components:
  schemas:

    SetDeliveryModeRequest:
      type: object
      required:
        - requestType
      properties:
        requestType:
          type: string

    PickupDeliveryRequest:
      allOf:
        - $ref: '#/components/schemas/SetDeliveryModeRequest'
        - type: object
          required:
            - pickupLocation
          properties:
            pickupLocation:
              type: string

Generation Details

Generator:

spring

Generator options:

documentationProvider=springdoc
useSpringBoot4=true
useJackson3=true

Steps to reproduce
Generate the Spring models.
Inspect the generated classes.

Generated base interface:

@JsonSubTypes({
    @JsonSubTypes.Type(
        value = PickupDeliveryRequest.class,
        name = "pickupDelivery"
    )
})

Generated subtype:

@JsonTypeName("PickupDeliveryRequest")
Serialize
new PickupDeliveryRequest("pickupDelivery", "STORE001")

Actual JSON:

{
  "requestType": "PickupDeliveryRequest",
  "pickupLocation": "STORE001"
}

Expected JSON:

{
  "requestType": "pickupDelivery",
  "pickupLocation": "STORE001"
}

Changing

@JsonTypeName("PickupDeliveryRequest")

to

@JsonTypeName("pickupDelivery")

causes serialization to work correctly.

Related issues/PRs

I searched for discriminator-related issues but could not find one describing this specific regression where the generated @JsonSubTypes.Type(name=...) and @JsonTypeName(...) disagree.

[seonwooj0810]

I tried to reproduce this on the spring generator with documentationProvider=springdoc,useSpringBoot4=true,useJackson3=true, on both 7.23.0 and current master (7.24.0-SNAPSHOT), but couldn't get the wrong @JsonTypeName:

• With the spec exactly as posted (a single-member oneOf), the oneOf collapses on both versions — no oneOf interface and no @JsonTypeName are generated on PickupDeliveryRequest at all, so the symptom doesn't appear.
• With a two-member oneOf using the same discriminator + mapping, both versions generate the SetDeliveryRequest interface with the correct type ids:

  @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "requestType", visible = true)
  @JsonSubTypes({
    @JsonSubTypes.Type(value = PickupDeliveryRequest.class, name = "pickupDelivery"),
    @JsonSubTypes.Type(value = HomeDeliveryRequest.class,   name = "homeDelivery")
  })

  and @JsonTypeName is suppressed on the child classes (hasDiscriminatorWithNonEmptyMapping), so Jackson serializes using the mapping value (pickupDelivery) — the expected behavior.

Could you share a complete spec that reproduces @JsonTypeName("PickupDeliveryRequest") on the child, plus the full generator config (e.g. whether useOneOfInterfaces or a modelNameSuffix/modelNamePrefix is set)? The posted oneOf has only one member, which is likely a reduction artifact. If you're able to test against 7.24.0-SNAPSHOT, that would help confirm whether it's already resolved for your real spec.

[jpfinne]

@vmjaws I agree with @seonwooj0810. I can't reproduce with your sample.
@seonwooj0810 you can keep the oneOf by disabling the SIMPLIFY_ONEOF_ANYOF normalizer.

The generation of JsonTypeName is handled in the pojo.mustache template:

{{#jackson}}
{{#isClassnameSanitized}}
{{^hasDiscriminatorWithNonEmptyMapping}}
@JsonTypeName("{{name}}")
{{/hasDiscriminatorWithNonEmptyMapping}}
{{/isClassnameSanitized}}
{{/jackson}}

The JsonTypeName should not exist if there is no modelNameSuffix ({{#isClassnameSanitized}})
The JsonTypeName should be removed even with modelNameSuffix ({{^hasDiscriminatorWithNonEmptyMapping}})
See my recent fix #24024 and the sample in #23997. It is on 7.24.0-SNAPSHOT.

Demo with unit test

    @Test
    void issue_24198() throws IOException {
        String suffix = "DTO";
        Map<String, File> files = generateFromContract(
                "src/test/resources/3_0/spring/issue_24198.yaml", SPRING_BOOT,
                Map.of(USE_SPRING_BOOT4, true,
                        MODEL_NAME_SUFFIX, suffix,
                        INTERFACE_ONLY, "true"),
                codegenConfigurator -> codegenConfigurator.addOpenapiNormalizer("SIMPLIFY_ONEOF_ANYOF", "false"));
        JavaFileAssert.assertThat(files.get("SetDeliveryRequest"+ suffix + ".java")).isInterface()
                .assertTypeAnnotations()
                .containsWithNameAndAttributes("JsonTypeInfo", Map.of("use", "JsonTypeInfo.Id.NAME", "include", "JsonTypeInfo.As.PROPERTY", "property", "\"requestType\"", "visible", "true"))
                .containsWithName("JsonSubTypes")
                .recursivelyContainsWithNameAndAttributes("JsonSubTypes.Type", Map.of("value", "PickupDeliveryRequest"+ suffix + ".class", "name", "\"pickupDelivery\""))
        ;

        JavaFileAssert.assertThat(files.get("PickupDeliveryRequest"+suffix + ".java")).implementsInterfaces("SetDeliveryRequest" + suffix)
                .fileDoesNotContain("@JsonTypeName");
    }

[vmjaws]

I investigated this further and i have another related issue, and reduced it to Jackson polymorphic deserialization.

The generated interface contains with latest version 7.23:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY,  property = "mergeCartStrategy",  visible = true)
@JsonSubTypes({
    @JsonSubTypes.Type(value = xxxV3KeepAnonymousCartMergeRequest.class, name = "KEEP_ANONYMOUS_CART"),
    @JsonSubTypes.Type(value = xxV3KeepGuestCartMergeRequest.class, name = "KEEP_GUEST_CART")
})

on 7.12 version:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "mergeCartStrategy", visible = true)
@JsonSubTypes({
  @JsonSubTypes.Type(value = xxxKeepAnonymousCartMergeRequest.class, name = "KEEP_ANONYMOUS_CART"),
  @JsonSubTypes.Type(value = xxxKeepGuestCartMergeRequest.class, name = "KEEP_GUEST_CART"),
  @JsonSubTypes.Type(value = xxxKeepAnonymousCartMergeRequest.class, name = "KeepAnonymousCartMergeRequest"),
  @JsonSubTypes.Type(value = xxKeepGuestCartMergeRequest.class, name = "KeepGuestCartMergeRequest")
})

while the generated subtype contains

@JsonTypeName("KeepAnonymousCartMergeRequest")
public class xxxV3KeepAnonymousCartMergeRequest ...

The incoming payload is

{
  "mergeCartStrategy": "KeepAnonymousCartMergeRequest"
}

With OpenAPI Generator 7.12.x this deserializes successfully.

With OpenAPI Generator 7.23.x (same OpenAPI document, same application code, only generator/dependencies upgraded) deserialization fails with:

Could not resolve type id 'KeepAnonymousCartMergeRequest'
known type ids = [KEEP_ANONYMOUS_CART, KEEP_GUEST_CART]

I also reproduced this outside of Spring by deserializing directly with Jackson:

objectMapper.readValue(json, xxxV3MergeCartsRequest.class);

which produces the same exception.

As an experiment, I manually added:

@JsonSubTypes.Type(
    value = xxxV3KeepAnonymousCartMergeRequest.class,
    name = "KeepAnonymousCartMergeRequest")

and deserialization succeeds again.

This suggests that newer generated code/runtime no longer treats @JsonTypeName as an accepted discriminator id and only accepts the explicit names declared in @JsonSubTypes.

Is this an intentional change, or a regression compared to 7.12.x?

The OpenAPI document itself is unchanged. The only change between the working and failing versions is upgrading the OpenAPI Generator (and its generated code/dependencies). The generated model classes are effectively identical except for unrelated annotation additions.

Have this in my gradle task to build the api specs

...
        globalProperties = [
            models: "",
            apis: "false",
        ]
        configOptions = [
            hideGenerationTimestamp: "true",
            sourceFolder: "src/main/java",
            modelTests: "false",
            documentationProvider: "springdoc",
            useSpringBoot4: "true",
            useJakartaEe           : "true",
            useJackson3: "true",
        ]
        additionalProperties = [
            enumPropertyNaming: "legacy"
        ]
...

this are the versions i have updated to:

`[versions]
avro = "1.9.1"
commonsCollections4 = "4.5.0"
commonsIo = "2.22.0"
commonsLang3 = "3.20.0"
contextPropagation = "1.2.1"
gson = "2.14.0"
gradleTestRetry = "1.6.4"
jakartaServlet = "6.2.0-M2"
jacksonDatabindNullable = "0.2.10"
jose4j = "0.9.6"
logstashLogbackEncoder = "9.0"
lombok = "1.18.46"
mapstruct = "1.6.3"
mockitoInline = "5.2.0"
mockwebserver = "5.4.0"
openapiGenerator = "7.23.0"
springBoot = "4.1.0"
springSecurity = "7.1.0"
swaggerAnnotations = "2.2.49"
testng = "7.12.0"
gradleTaskTree = "4.0.1"
springdoc = "3.0.3"
lombokMapstructBinding = "0.2.0"
springRetry = "2.0.13"

[libraries]
spring-boot-starter-data-jpa = { group = "org.springframework.boot", name = "spring-boot-starter-data-jpa" }
spring-boot-starter-oauth2-client = { group = "org.springframework.boot", name = "spring-boot-starter-security-oauth2-client" }
spring-boot-starter-oauth2-resource-server = { group = "org.springframework.boot", name = "spring-boot-starter-security-oauth2-resource-server" }
spring-boot-starter-security = { group = "org.springframework.boot", name = "spring-boot-starter-security" }
spring-boot-starter-test = { group = "org.springframework.boot", name = "spring-boot-starter-test" }
spring-boot-starter-validation = { group = "org.springframework.boot", name = "spring-boot-starter-validation" }
spring-boot-starter-web = { group = "org.springframework.boot", name = "spring-boot-starter-webmvc" }
spring-boot-starter-webflux = { group = "org.springframework.boot", name = "spring-boot-starter-webflux" }

spring-security-test = { group = "org.springframework.security", name = "spring-security-test", version.ref = "springSecurity" }
spring-boot-starter-cache = { group = "org.springframework.boot", name = "spring-boot-starter-cache" }

#springfox-swagger2 = { group = "io.springfox", name = "springfox-swagger2", version.ref = "springfoxSwagger" }
#springfox-swagger-ui = { group = "io.springfox", name = "springfox-swagger-ui", version.ref = "springfoxSwagger" }

spring-kafka-impl = { group = "org.springframework.boot", name = "spring-boot-starter-kafka", version.ref = "springBoot" }
kafka-avro-serializer = { group = "io.confluent", name = "kafka-avro-serializer", version.ref = "kafkaAvroSerializer" }

swagger-annotations = { group = "io.swagger.core.v3", name = "swagger-annotations", version.ref = "swaggerAnnotations" }
commons-io = { group = 'commons-io', name = 'commons-io', version.ref = "commonsIo" }
commons-lang3 = { group = "org.apache.commons", name = "commons-lang3", version.ref = "commonsLang3" }
commons-collections4 = { group = "org.apache.commons", name = "commons-collections4", version.ref = "commonsCollections4" }
mapstruct = { group = "org.mapstruct", name = "mapstruct", version.ref = "mapstruct" }
mapstruct-processor = { group = "org.mapstruct", name = "mapstruct-processor", version.ref = "mapstruct" }
jakarta-servlet-api = { group = "jakarta.servlet", name = "jakarta.servlet-api", version.ref = "jakartaServlet" }
drools-compiler = { group = "org.drools", name = "drools-compiler", version.ref = "drools" }
drools-core = { group = "org.drools", name = "drools-core", version.ref = "drools" }
drools-mvel = { group = "org.drools", name = "drools-mvel", version.ref = "drools" }
drools-xml-support = { group = "org.drools", name = "drools-xml-support", version.ref = "drools" }

context-propagation = { group = "io.micrometer", name = "context-propagation", version.ref = "contextPropagation" }
gson = { group = "com.google.code.gson", name = "gson", version.ref = "gson" }
jackson-databind-nullable = { group = "org.openapitools", name = "jackson-databind-nullable", version.ref = "jacksonDatabindNullable" }
jose4j = { group = "org.bitbucket.b_c", name = "jose4j", version.ref = "jose4j" }
logstash-logback-encoder = { group = "net.logstash.logback", name = "logstash-logback-encoder", version.ref = "logstashLogbackEncoder" }
lombok = { group = "org.projectlombok", name = "lombok", version.ref = "lombok" }
mockito-inline = { group = "org.mockito", name = "mockito-inline", version.ref = "mockitoInline" }
mockwebserver = { group = "com.squareup.okhttp3", name = "mockwebserver", version.ref = "mockwebserver" }
testng = { group = "org.testng", name = "testng", version.ref = "testng" }

ff4j = { group = "org.ff4j", name = "ff4j-core", version = "2.1" }
spring-cloud-aws= { group = "io.awspring.cloud", name = "spring-cloud-aws", version.ref = "springCloudAws" }

spring-boot-starter-tomcat = { group = "org.springframework.boot", name = "spring-boot-starter-tomcat" }
springdoc-openapi-webmvc-ui = { group = "org.springdoc", name = "springdoc-openapi-starter-webmvc-ui", version.ref = "springdoc" }
spring-boot-starter-restclient = { group = "org.springframework.boot", name = "spring-boot-starter-restclient", version.ref = "springBoot" }
lombok-mapstruct-binding = { group = "org.projectlombok", name = "lombok-mapstruct-binding", version.ref = "lombokMapstructBinding" }
spring-boot-starter-webmvc-test = { group = "org.springframework.boot", name = "spring-boot-starter-webmvc-test", version.ref = "springBoot" }
spring-boot-webtestclient = { group = "org.springframework.boot", name = "spring-boot-webtestclient", version.ref = "springBoot" }
spring-retry = { group = "org.springframework.retry", name = "spring-retry", version.ref = "springRetry" }

[plugins]
gradle-git-properties = { id = "com.gorylenko.gradle-git-properties", version.ref = "gradleGitProperties" }
openapi-generator = { id = "org.openapi.generator", version.ref = "openapiGenerator" }
spring-boot = { id = "org.springframework.boot", version.ref = "springBoot" }

gradle-test-retry = { id = "org.gradle.test-retry", version.ref = "gradleTestRetry" }
gradle-task-tree = { id = "com.dorongold.task-tree", version.ref = "gradleTaskTree" }
`

[jpfinne]

@vmjaws without the api, it is difficult to investigate.

My guess is that on 7.24.0-SNAPSHOT you won't have the JsonTypeName in

public class xxxV3KeepAnonymousCartMergeRequest 

The JsonSubTypes should be enough

[vmjaws]

@jpfinne thank you for your update.
How can I securely provide the api spec to you.
Kind regards.

[jpfinne]

@jpfinne thank you for your update. How can I securely provide the api spec to you. Kind regards.

First try 7.24.0-SNAPSHOT

It it does not work, create a minimalistic api that reproduce it and share it here