Spring Web Reactive Framework Multipart File Issue

After digging around I was able to find this test in the Spring WebFlux project:

https://github.com/spring-projects/spring-framework/blob/master/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/MultipartIntegrationTests.java

So the part I was missing was @RequestPart instead of @RequestBody in the controller definition.

Final code looks something like this:

@RestController
@RequestMapping("/images")
public class ImageController {

    @Autowired
    private IImageService imageService;

    @PostMapping(value = "", consumes = MediaType.MULTIPART_FORM_DATA_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
    Mono<ImageEntity> saveImage(@RequestPart("file") Mono<FilePart> part) throws Exception{
         return part.flatMap(file -> imageService.saveImage(file));
    }
}

Actually the following solution seems to work with Netty

    @PostMapping(path = "/test/{path}",
            consumes = MediaType.MULTIPART_FORM_DATA_VALUE, 
            produces = {MediaType.APPLICATION_JSON_VALUE})
    @ResponseBody
    Mono<String> commandMultipart(
        @PathVariable("path") String path,
        @RequestPart("jsonDto") Mono<JsonDto> jsonDto,
        @RequestPart(value = "file",required = false) Mono<FilePart> file) {
        JsonDto dto = jsonDto.block();
     }

Build.gradle

 compile group: 'org.synchronoss.cloud', name: 'nio-multipart-parser', version: '1.1.0'

 compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.9.3'
 compile group: 'com.fasterxml.jackson.datatype', name: 'jackson-datatype-jsr310', version: '2.9.3'

curl command in bash

echo '{"test":"1"}' > command.json && curl -H "Content-Type:multipart/form-data" -X POST http://localhost:8082/test/examplepath/ -F "command=@./command.json;type=application/json" -F "[email protected]" -vv

Troubleshooting steps

1. Ensure nio-multipart-parser is present by checking method org.springframework.http.codec.support.ServerDefaultCodecsImpl#extendTypedReaders

2. You can check that nio-multipart-parser is used by placing breakpoint inside

   • org.springframework.http.codec.multipart.SynchronossPartHttpMessageReader#canRead() for single part
   • org.springframework.http.codec.multipart.MultipartHttpMessageReader#canRead for multipart

   One of the above methods should return true.