The problem was in Configuration class, in Docket Bean.
Here I'm defining route to my Controllers to exclude others from swagger-ui.
The problem was in DocumentationType, OpenApi3.0 is maintaining multitype files uploading, and Swagger2 don't.

Next problem which I faced was:
415 Unsupported Media Type
Resolution:
First way:
If you will use postman/javaScript framework -> you have to define media-type of every RequestPart (actually don't need for file, for file it will be set automatically).
example in POSTMAN:

Second way: is implement maintaining of octet-stream, because spring set it by default in AbstractMessageConverterMethodArgumentResolver.class
if there is no content-type header in request part.
(I'm using spring-boot-starter-parent 2.4.1 -> spring-webmvc 5.3.2
)

So here is 2 cases I found (to map response JSON to DTO):
1 case (not recommended):
Set supporting to JSON converter:

2 case:
Define new Converter class which will work definitely for needed classes (in my case it is MDVersionDTO.class
) and definitely when it comes like octet-stream, to implement it, ovveride canRead()
method.

UPDATE FOR SPRING-BOOT 2.7.0
Faced again, and now DocumaentationType.OAS_30 not working...
So, to resolve:
- I implemented same MultipartJSONConverter and made it @Component
- I used DocumaentationType.SWAGGER_2
- Removed @RequestBody annotation and used like this:

In this case you will have ability to upload files with request Body, but you will not have model example in swagger, it will be empty.
