如何修复 Spring 引导分段上传中的“所需请求部分不存在”

Question

While my question is similar to this one , I am not using the MockMultipartFile . Here my use case.

In a Spring Boot 2.4.5 application, I have written a unit test which executes code, that should send a multipart/form-data request. To be able to test the receiving end from the test, I have started a Controller as a receiver for the multipart/form-data call. This is the controller (it is currently not doing anything with the parameters).

import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

@RestController
@RequestMapping("/v1/api")
public class VideoServiceStub {
    @PostMapping(value ="/videoservice/videos", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public ResponseEntity<String> upload(@RequestPart("name") MultipartFile name, @RequestPart("file") MultipartFile file) {
        return ResponseEntity.status(HttpStatus.OK).body("it works");
    }
}

What makes my use case special, is that the POST shall be made from an in-memory byte array or InputStream . To give some context, my code will later download a file from a URL and make this multipart/form-data to relay the data and send it someplace else. The unit test will trigger the following code to execute, which uses Spring Rest Template.

protected void sendToVideoService(String name, byte[] content) {
        var headers = new HttpHeaders();
        headers.setContentType(MediaType.MULTIPART_FORM_DATA);

        var body = new LinkedMultiValueMap<>();
        body.add("name", name);
        body.add("file", new ByteArrayResource(content));

        var url = this.uploadUrl();  // the test will return the correct localhost URL here

        var requestEntity = new HttpEntity<>(body, headers);
        restTemplate.postForEntity(url, requestEntity, String.class);        
    }

It fails with a HttpClientErrorException$BadRequest and I can see this in the stdout logs:

2021-06-01 07:23:33.027  WARN 27432 --- [o-auto-1-exec-2] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.multipart.support.MissingServletRequestPartException: Required request part 'name' is not present]

To verify, that the problem was on the receiving end, I tested a version using the newer java.net.http.HttpClient together with the great methanol library.

protected void sendToVideoServiceUsingJava11(String name, byte[] content) {
    var url = this.uploadUrl(); // the test will return the correct localhost URL here
    var methanol = Methanol.create();
    var multipartBody = MultipartBodyPublisher.newBuilder()
            .textPart("name", name)
            .formPart("file", HttpRequest.BodyPublishers.ofByteArray(content))
            .build();

    var request = MutableRequest.POST(url, multipartBody);
    methanol.send(request, HttpResponse.BodyHandlers.ofString());
}

I can see the exact same warning in stdout:

2021-06-01 07:22:35.086  WARN 23840 --- [o-auto-1-exec-2] .w.s.m.s.DefaultHandlerExceptionResolver : 
Resolved [org.springframework.web.multipart.support.MissingServletRequestPartException: Required request part 'name' is not present]
400

Finally, I have this in my application.yaml :

spring:
  servlet:
    multipart:
      max-file-size: 750MB
      max-request-size: 750MB

server:
  tomcat:
    max-swallow-size: 786432000
    max-http-form-post-size: 786432000

logging:
  level:
    org:
      springframework:
        web:
          filter:
            CommonsRequestLoggingFilter: DEBUG

Answer 1

I managed to solve the issue. In the VideoServiceStub the name param must be a String instead of a MultipartFile .

@PostMapping(value ="/videoservice/videos", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public ResponseEntity<String> upload(@RequestPart("name") String name, @RequestPart("file") MultipartFile file) {
    return ResponseEntity.status(HttpStatus.OK).body("it works");
}

Furthermore in sendToVideoServiceUsingJava11 , it doesn't work without a filename :

.formPart("file", "filename.mp4", HttpRequest.BodyPublishers.ofByteArray(content))

I never got the Spring REST Template example to work. There is no way to pass a filename along when doing: body.add("file", new ByteArrayResource(content)) . Maybe someone has an idea?