Transitioning from Spring Boot 2.x to 3.x: Converting Flux<Part> to MultipartFile

Question

I'm in the process of migrating from Spring Boot 2.x to Spring Boot 3.x. In Spring Boot 2.x, I was using MultipartFile for file uploads, which worked perfectly. However, with the introduction of WebFlux in Spring Boot 3.x, I've realized that to process multipart data in a streaming fashion, I need to use Flux returned from an HttpMessageReader instead of MultipartFile.

Since my code heavily relies on MultipartFile, I'd like to minimize changes to the existing code. Is there a way to convert Flux to MultipartFile seamlessly?

Here's the code for comparison:

With Spring MVC (Spring Boot 2.x):

@PostMapping(value = "/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<?> upload(@RequestPart(value = "file", required = false) MultipartFile file) {
    // Existing code for Spring MVC
}

With Spring WebFlux (Spring Boot 3.x):

@PostMapping(value = "/upload", consumes = MediaType.MULTIPART_FORM_DATA_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<?> upload(@RequestPart(value = "file", required = false) Flux<Part> file) {
    // Updated code for Spring WebFlux
}

Is there a way to make this transition with minimal code changes?