Spring Boot multipart upload getting null file object

Question

I am getting a problem while implementing multipart file upload using spring boot 1.5.2.

Here is the situation, I have a mapping to handle file upload process.While I start the spring server, it starts without any error. The problem is that I would either able to upload the file perfectly fine or I would get null on all attribute in FileBucket object .

This situation would stay forever if I do not shutdown the server.

• If it could upload, it would upload fine for the rest of the time.
• If not, it won't work until I restart the server(likely more than one time)

Here is the mapping.

@RequestMapping(value = {"/api/upload"}, method = RequestMethod.POST)
public ResponseEntity<Map<String, Integer>> upload(@Valid FileBucket fileBucket, BindingResult result) throws IOException {
        Session session = sessionFactory.openSession();
        User user = (User) session.load(User.class, getUserId());

        Map<String, Integer> model = new HashMap<String, Integer>();
        if (result.hasErrors()) {
            System.out.println("validation errors");
            System.out.println(result);
            session.close();
            return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
        } else {
            int documentId = saveDocument(fileBucket, user);
            model.put("documentId", documentId);
            session.close();
            return new ResponseEntity<Map<String, Integer>>(model, HttpStatus.OK);
        }
}

And the FileBucket object

public class FileBucketConversation {

    private MultipartFile file;

    public MultipartFile getFile() {
        return file;
    }

    public void setFile(MultipartFile file) {
        this.file = file;
    }
}

I have tried few ways to implement file upload, and still having the same situation.

1. Using StandardServletMultipartResolver .

    @Bean(name = "multipartResolver") public StandardServletMultipartResolver resolver() { return new StandardServletMultipartResolver(); } 

2. Using CommonsMultipartResolver v1.3.2.

    @Bean(name="multipartResolver") public CommonsMultipartResolver multipartResolver () { CommonsMultipartResolver resolver = new CommonsMultipartResolver(); resolver.setMaxUploadSize(MAX_FILE_SIZE); return resolver; } 

   overriding MultipartFilter

    @Bean @Order(0) public MultipartFilter multipartFile() { MultipartFilter multipartFilter = new MultipartFilter(); multipartFilter.setMultipartResolverBeanName("multipartResolver"); return multipartFilter; } 

3. Enable spring.http.multipart in properties file

    spring.http.multipart.enabled=true spring.http.multipart.max-file-size=20Mb spring.http.multipart.max-request-size=20Mb 

I really have no clue where to start looking. The problem happen occasionally, it do not happen every time I start the server but most of the time. Hoping some one could help me.

Thank you.

Answer 1

I had the same problem, this is my solution:

In application.yml:

spring:
  http:
    multipart:
      enabled: false

In configuration:

import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;
...

@Bean
public MultipartResolver multipartResolver() {
    return new CommonsMultipartResolver();
}

In RestController:

@PostMapping(value = "api/upload", consumes = "multipart/form-data") 
public void enablePurchase(@RequestHeader HttpHeaders headers,
                           FileBucketConversation fileBucketConversation) {
...
}

Important: In your client don't use any header to define the Content-type or boundary. I'm using Angular 4 and when I remove these headers from my code it works (I only set the User token):

/* DON'T USE THIS:
let boundary = "ABDCE";
headers.append("Content-type", "multipart/form-data;boundary=" + boundary);
headers.append("enctype", "multipart/form-data;boundary=" + boundary);
headers.append("boundary", boundary);
*/

I hope this help you.

Answer 2

Update for Spring Boot 2 and Spring 5

spring.http.multipart.enabled is deprecated, so forget about it.

Registering my own beans for MultipartConfigElement or MultipartResolver broke it for me.

I ended up with a @PostMapping method with a single parameter, @RequestPart(name = "file") MultipartFile file . Adding a parameter @RequestHeader HttpHeader headers helped me make sure the client was sending the required header Content-Type with a boundary.

I'm using a Node client with the form-data library and node-fetch . Here's the client code:

const formData = new FormData();
const fileMetadata = {filename: fileName, contentType: 'image/png', knownLength: fs.statSync(pathToFile)};
const formData.append('file', fs.createReadStream(pathToFile), fileMetadata);
fetch(url, {method: 'POST', body: formData});