[BUG] [JAVA] oneOf generates incorrect model for primitive types

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)

Description

Using oneOf will generate a model with incorrect wrong types.

Actual output: I have three files of models: ClientIp.java, Request,java, Response.java. Request.java has field private ClientIp clientIp = null; with type ClientIp

Expected output: I have only two files of models: Request,java, Response.java. Request.java has field private String clientIp; with string type

openapi-generator version

openapi-generator-cli 5.2.1 commit : 8403e59 built : 2021-08-16T12:52:51Z source : https://github.com/openapitools/openapi-generator docs : https://openapi-generator.tech/

openapi-generator-cli 5.3.0-SNAPSHOT commit : de95e2a built : 2021-09-22T15:38:29+04:00 source : https://github.com/openapitools/openapi-generator docs : https://openapi-generator.tech/

OpenAPI declaration file content or url

openapi: 3.0.3

info:
  title: java codegen BUG
  description: oneOf generates incorrect model for primitive types
  version: 1.0.0

paths:
  /openapi/example/path:
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Request'
      responses:
        200:
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Response'

components:
  schemas:
    ClientIp:
      oneOf:
        - type: string
          format: ipv4
        - type: string
          format: ipv6
      nullable: false
      example: '127.0.0.1' # or '2001:0db8:85a3:0000:0000:8a2e:0370:7334' for IPv6

    Response:
      properties:
        result:
          type: string

    Request:
      properties:
        result:
          type: string
        client_ip:
          $ref: "#/components/schemas/ClientIp"

Generation Details

java -jar openapi-generator-cli.jar generate -g java -i oneOfbug.yaml -o .\gen\

Steps to reproduce

Generate a java client using the above yaml.

Related issues/PRs

it little bit similar to https://github.com/OpenAPITools/openapi-generator/issues/4130

Suggest a fix

[dilook]

@wing328 I’ve just researched and known that it’s happened for libraries: resttemplate, default okhttp-gson (like in bug).

With native library and jersey2 all is OK. Abstract-class (AbstractOpenApiSchema) is generated with constructor of String type parameter. So it seems that problem is in generation code for specific libraries.

[ldiaz2-chwy]

–library jersey2

ive tried both native and jersey2 and the oneof class is not generated. Is there a workaround?

Using something like so :

method-account: oneOf: - $ref: ‘#/components/schemas/AccountA’ - $ref: ‘#/components/schemas/AccountB’ - $ref: ‘#/components/schemas/AccountC’ - $ref: ‘#/components/schemas/AccountD’ discriminator: propertyName: account-type