"Error-ModelName{namespace='java.lang', name='Void'}" in 3.0.0 springfox + webflux

I have Docket configured like that:

        Docket docket = new Docket(DocumentationType.SWAGGER_2)
            .alternateTypeRules(
                newRule(
                    typeResolver.resolve(List.class, LocalDateTime.class),
                    typeResolver.resolve(List.class, String.class)
                ),
                newRule(
                    typeResolver.resolve(List.class, LocalDate.class),
                    typeResolver.resolve(List.class, String.class)
                )
            )
            .apiInfo(apiInfo)
            .securitySchemes(Collections.singletonList(oauth()))
            .securityContexts(List.of(securityContext()))
            .forCodeGeneration(true)
            .directModelSubstitute(java.nio.ByteBuffer.class, String.class)
            .genericModelSubstitutes(Mono.class, Flux.class, Publisher.class)
            .host(host)
            .protocols(protocols)
            .select()
            .apis(RequestHandlerSelectors.withClassAnnotation(RestController.class))
            .paths(regex(swaggerProperties.getDefaultIncludePattern()))
            .build();

And have an API method that return Flux<Void>

    @PostMapping("refresh")
    public Flux<Void> refresh() {
        return callsProvider.refresh().subscribeOn(Schedulers.elastic());
    }

But in JSON I’ve got an error:

                "responses": {
                    "200": {
                        "description": "OK",
                        "schema": {
                            "type": "array",
                            "items": {
                                "$ref": "Error-ModelName{namespace='java.lang', name='Void'}",
                                "originalRef": "Error-ModelName{namespace='java.lang', name='Void'}"
                            }
                        }
                    },

Adding .ignoredParameterTypes(Void.class) to Docket didn’t help.

[ajurasz]

I came across similar issue yesterday. But in my case from what I can see it is related to consuming multipart/form-data ie.

    @PutMapping(value = "/{name}/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    @ApiOperation(value = "Sample upload method")
    ResponseEntity<Void> test(
            @ApiParam(value = "Name", required = true) @PathVariable String name,
            @ApiParam(value = "Uploaded file", required = true) @RequestPart("file") MultipartFile file
    ) {
        return ResponseEntity.accepted().build();
    }

then I got the same error as in issue title, but JSON was a little bit different:

        "responses": {
          "200": {
            "description": "OK",
            "schema": {
              "$ref": "#/definitions/Error-ModelName{namespace='java.lang', name='Void'}"
            }
          }
      }

For now, I have workaround were I explicitly override 200 status code with:

    @ApiResponses({
            @ApiResponse(code = 200, message = "OK")
    })

EDIT:

While trying to debug the issue I have found the following property:

springfox.documentation.swagger.use-model-v3

which fixes the above issue when set to false as it does not use open API v3.

[ManolisPapd]

Maybe it’s not suitable for everyone but a workaround in my case was to remove a redundant produces attribute from HTTP method annotations.

For example:

@PutMapping(path = "/test", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<Void>(....)

Changed to:

@PutMapping(path = "/test")
public ResponseEntity<Void>(....)