[REQ] [JAVA] [SPRING] Add a way to pass the content type as a method parameter

[claudiusnuss]

Is your feature request related to a problem? Please describe.

I use Java and the OpenApi generator to generate classes, that use the SpringBoot resttemplate or restClient to send requests through defined REST-endpoints. These requests can have different bodies and with that different content-types. I can only set the content-type of the request through the definition of the endpoint.

Describe the solution you'd like

I would like an option, that adds a content-type method parameter. With that I can manually set the content-type of the request.

[Picazsoo]

Hi @claudiusnuss, I am not a maintainer, but here are my 2 cents anyway - the problem with MediaType parameter approach is it breaks down as soon as request body schemas differ per content type. That is quite common (e.g. application/json vs multipart/form-data have completely different shapes).

A cleaner approach would be to generate multiple methods when an operation defines multiple request body content types - one per content type - with the content type suffix appended to the operationId. So for a createPet operation with both application/json and multipart/form-data bodies:

public ResponseEntity<Pet> createPetApplicationJson(PetJson body)
public ResponseEntity<Pet> createPetMultipartFormData(PetForm body)

This would keep each method strongly typed to its schema and it avoids ambiguity at the call site, and handles differing schemas naturally. It's also consistent with how the generator already handles other operation variants through operationId suffixing.

I recall this approach already being used in some other generators.