Multipartfile parameter order precedence causing error

Question

Basically, I am sending two parameters , one a String and the other a file to my controller in Spring Boot . In the action, when I receive the file first and then the String next, like so

@RequestMapping(value = "/updatemedia", method = RequestMethod.PATCH,consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public ResponseEntity<String> updateMedia(@RequestParam(value ="file") MultipartFile fileToUpload , @RequestParam(value = "keyId") String keyId )

everything is fine and I am able to access the String and the file correctly.

But when I change the order of the parameters , like so

@RequestMapping(value = "/updatemedia", method = RequestMethod.PATCH,consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public ResponseEntity<String> updateMedia( @RequestParam(value = "keyId") String keyId , @RequestParam(value ="file") MultipartFile fileToUpload )

and send the params through Postman, I am hitting the below error

I researched a lot but am not able to understand this behaviour.

Answer 1

Because you send keyId in body while it's declared as @RequestParam https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestParam.html . @RequestParam has nothing to deal with request body, it's passed in request url. What about your example, the first approach works, because your method expects one @RequestPart, the others are ignored.