Spring Boot Swagger duplicate model type when using inheritance

I've a Java project that uses Spring Boot and Swagger. The project consists of a simple API controller that implements a single endpoint. Invoking the GET method on the endpoint gets all users. Invoking the PUT method on the same endpoint updates a single user:

@RestController
@RequestMapping("/api/v1/users")
public class UserController {
    @RequestMapping(value = "", method = RequestMethod.GET)
    public List<BaseUser> getUsers(String name) {
        return null;
    }

    @RequestMapping(value = "", method = RequestMethod.PUT)
    public BaseUser updateUser(@RequestBody BaseUser user) {
        return null;
    }
}

The /api/v1/users endpoint is implemented using a BaseUser which has subtypes like EmployeeUser:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
@JsonSubTypes({
        @JsonSubTypes.Type(value = EmployeeUser.class, name = "employee")
})
public abstract class BaseUser {

    private final int id;
    private final String name;

    @JsonCreator
    protected BaseUser(
            @JsonProperty("id") int id,
            @JsonProperty("name") String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }
}

public class EmployeeUser extends BaseUser {
    public EmployeeUser(@JsonProperty("id") int id,
                     @JsonProperty("name") String name) {
        super(id, name);
    }
}

With this structure, when I browse the Swagger UI I see duplicates of these model types (based on the definitions in the OpenAPI spec).

I expected to see only a single BaseUser and a single EmployeeUser. What is the reason for the duplicates?

Definitions from OpenAPI Spec:

"definitions": {
    "BaseUserReq": {
        "type": "object",
        "discriminator": "type",
        "properties": {
            "id": {
                "type": "integer",
                "format": "int32"
            },
            "name": {
                "type": "string"
            }
        },
        "title": "BaseUserReq"
    },
    "BaseUserRes": {
        "type": "object",
        "discriminator": "type",
        "properties": {
            "id": {
                "type": "integer",
                "format": "int32"
            },
            "name": {
                "type": "string"
            }
        },
        "title": "BaseUserRes"
    },
    "EmployeeUserReq": {
        "title": "EmployeeUser",
        "allOf": [{
            "$ref": "#/definitions/BaseUserReq"
        }, {
            "type": "object",
            "properties": {
                "id": {
                    "type": "integer",
                    "format": "int32"
                },
                "name": {
                    "type": "string"
                }
            },
            "title": "EmployeeUserReq"
        }]
    },
    "EmployeeUserRes": {
        "title": "EmployeeUser",
        "allOf": [{
            "$ref": "#/definitions/BaseUserRes"
        }, {
            "type": "object",
            "properties": {
                "id": {
                    "type": "integer",
                    "format": "int32"
                },
                "name": {
                    "type": "string"
                }
            },
            "title": "EmployeeUserRes"
        }]
    }
}

I've had a similar and other problems with version 3.0.0., so I still use 2.9.2 in my projects. You can try the following as an alternative.

When changing dependencies (removed springfox-bean-validators, springfox-boot-starter) in your test project to:

<dependency>
   <groupId>io.springfox</groupId>
   <artifactId>springfox-swagger2</artifactId>
   <version>2.9.2</version>
</dependency>
<dependency>
   <groupId>io.springfox</groupId>
   <artifactId>springfox-swagger-ui</artifactId>
   <version>2.9.2</version>
</dependency>

... and changing SwaggerConfig (removing missing imports after changed dependencies) to:

@Configuration
@EnableSwagger2
public class SwaggerConfig { }

... the Swagger UI endpoint at http://localhost:8080/swagger-ui.html will return classes you expect:

Also, you can remove spring-core dependecy since it is already packed within the spring-boot-starter-web, maven-compiler-plugin dependency since it is a plugin, and remove duplicated maven compiler source and target definitions that are defined as properties and a second time as a configuration of the maven compiler plugin.

BaseUserReq, BaseUserRes, EmployeeUserReq and EmployeeUserRes are generated because Springfox 3.0 uses Swagger v3 models by default. You can disable it in application.properties.

> Springfox 3.0 uses v3 models by default. To workaround it for now,
> add: springfox.documentation.swagger.v2.use-model-v3=false in your
> application.properties.
> from https://github.com/springfox/springfox/issues/3503#issuecomment-684819445

After disabling springfox v3 models I got :

This issue is described here Suffix with number like "_1" is added to duplicated object name

> Hi, @pitzcarraldo. Thanks for the report.
>
> The intention for the last changes, that've been merged to master, and
> became available in the 3.0.0-SNAPSHOT version is to differ model with
> not symmetric properties. So if model has different properties for
> serialization and deserialization SpringFox will generate two models.
> "ModelName" for serialization and "ModelName_1" for deserialization or
> vise versa.
> from https://github.com/springfox/springfox/issues/3014#issuecomment-497941639

I fixed it by removing @JsonCreator and @JsonProperty in BaseUser and EmployeeUser constructors

As of springfox 3.0.0 swagger url is http://localhost:8080/swagger-ui/

See github repository https://github.com/ielatif/swagger-test

Commits history for explanations https://github.com/ielatif/swagger-test/commits/master

Inheritance works for me, but this happens in my project if I add any extra methods to the models (or maybe it's just methods named setXXX, getXXX and isXXX).

If I make my models simple Java beans with just setters and getters and no other logic, it makes a single schema object without Res or Req suffixes.