[Spring] can't handle multiple responses

[mwoodland]

Description

We have an OpenAPI spec file where we've defined multiple possible responses for an operation, however when the Spring code is generated the generated @RequestMapping method is only capable of returning the first response defined.

openapi-generator version

3.2.3

OpenAPI declaration file content or url

openapi: "3.0.0"
info:
  title: "Example"
  version: "1.0.0"
servers:
  - url: "/api/v1"
  - url: "/api/"
tags:
  - name: "example"
paths:
  "/example":
    get:
      tags:
        - "example"
      operationId: "examples"
      summary: "Get examples that match criteria"
      parameters:
      - name: "id"
        in: query
        description: "the identifier to get"
        required: true
      responses:
        200:
          description: "Success"
          content:
            application/json:
              schema:
                $ref: "#components/schemas/ExampleObject"
        404:
          description: "Failed to find the Example Object"
          content:
            application/json:
              schema:
                $ref: "#components/schemas/Errors"
components:
  schemas:
    "ExampleObject":
      type: object
      properties:
        "property1":
          type: string
        "property2":
          type: string
    "Errors":
      type: object
      properties:
        "code":
          type: integer
          format: int32
        "severity":
          type: string
        "message":
          type: string

Command line used for generation

<pluginExecutor>
    <plugin>
        <groupId>org.openapitools</groupId>
        <artifactId>openapi-generator-maven-plugin</artifactId>
        <version>3.2.3</version>
    </plugin>
    <goal>generate</goal>
    <configuration>
        <inputSpec>api-def/spec.yml</inputSpec>
        <generatorName>spring</generatorName>
        <output>api-gen</output>
        <modelNamePrefix>Api</modelNamePrefix>
        <configOptions>
            <basePackage>package</modelPackage>
            <apiPackage>package</apiPackage>
            <groupId>group</groupId>
            <artifactId>api-gen</artifactId>
            <artifactVersion>${project.version}</artifactVersion>
            <artifactDescription>Automatically generated interfaces for APIs</artifactDescription>
            <interfaceOnly>true</interfaceOnly>
        </configOptions>
    </configuration>
</pluginExecutor>

Steps to reproduce

Generate the Spring code using the specified spec file and maven configuration. The following @RequestMapping is generated:

    @ApiOperation(value = "Get examples that match criteria", nickname = "examples", notes = "", response = ApiExampleObject.class, tags={ "example", })
    @ApiResponses(value = { 
        @ApiResponse(code = 200, message = "Success", response = ApiExampleObject.class),
        @ApiResponse(code = 404, message = "Failed to find the Example Object", response = ApiErrors.class) })
    @RequestMapping(value = "/example",
        produces = { "application/json" }, 
        method = RequestMethod.GET)
    default ResponseEntity<ApiExampleObject> examples(@NotNull @ApiParam(value = "the identifier to get", required = true) @Valid @RequestParam(value = "id", required = true)  ) {
        getRequest().ifPresent(request -> {
            for (MediaType mediaType: MediaType.parseMediaTypes(request.getHeader("Accept"))) {
                if (mediaType.isCompatibleWith(MediaType.valueOf("application/json"))) {
                    ApiUtil.setExampleResponse(request, "application/json", "{  \"property2\" : \"property2\",  \"property1\" : \"property1\"}");
                    break;
                }
            }
        });
        return new ResponseEntity<>(HttpStatus.NOT_IMPLEMENTED);

    }

The return type is of ResponseEntity<ApiExampleObject> which means I can't return an ApiErrors object.

Related issues/PRs

Sounds similar to #316

Suggest a fix/enhancement

Get the method to return an object that can encapsulate one of the types defined in the response.

Or a simpler option is to get the method to return a ResponseEntity<Object>.