FeignClient: Multipart requests only work with @PathVariable parameters.

The following interface should be enough to handle multipart form requests:

@FeignClient(url = "http://localhost:8080")
public interface SpringFeignTestInterface {

    @RequestMapping(value = "/upload/{folder}", method = POST)
    public ResponseEntity<UploadInfo> upload(@PathVariable("folder") String folder, @RequestParam("file") MultipartFile file, @RequestParam("metadata") UploadMetadata metadata) ;

}

It doesn’t work, since the @RequestParam annotation (processed by this code) does not trigger multipart form generation, since it creates nameParams.

But if I use @PathVariable for all parameters, like the following:

@FeignClient(url = "http://localhost:8080")
public interface SpringFeignTestInterface {

    @RequestMapping(value = "/upload/{folder}", method = POST)
    public ResponseEntity<UploadInfo> upload(@PathVariable("folder") String folder, @PathVariable("file") MultipartFile file, @PathVariable("metadata") UploadMetadata metadata) ;

}

the multipart request is created correctly, since the @PathVariable parameters that aren’t actually in the URL, are processed as formParams, see here. Please note that at the moment I used my own implementation of Feign Encoder to build the multipart request correctly.

Maybe this weird behaviour of @PathVariable should be removed, and @RequestParam should trigger form creation if it contains MultiPartFiles or arrays of them. It would be great to see that Spring Feign could take full advantage of all REST Controller annotations (not to mention @RequestPart…).

[cbornet]

👍 for MultipartFile support

[spencergibb]

@antemooo please stop commenting the same thing on multiple issues