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 "file=@test.bin" -vv

Troubleshooting steps

1. Ensure nio-multipart-parser is present by checking methodorg.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.

In some cases the solution is to update the Spring version greater than 2.1.1, after this you should check that in the dependencies that are not 'spring-webmvc' since this generates a conflict with 'spring-boot-starter-webflux'