Spring Rest - Post multiple files

Question

Using Spring Boot 2.1.8, I have two methods in a Rest Controller that expect a single file and multiple files respectively. These are the method signatures:

@PreAuthorize("hasAnyRole('ROLE_ADMIN')") @PostMapping("/uploadMultipleFiles") public List<FileResponse> uploadMultipleFiles(@RequestParam("files") MultipartFile[] files); @PreAuthorize("hasAnyRole('ROLE_ADMIN')") @PostMapping("/upload") public FileResponse uploadFile(@RequestParam("file") MultipartFile file);

The single upload works just perfect. I am managing to load a single file from a web client, Postman v7.25.0, and from Swagger 2.

But the multiple file method only works when uploading files from Postman, returning a 400 http error code. Therefore, it does not even enter the method.

The error message in both cases (web client or Swagger) is the same:

can't parse JSON. Raw result: Missing or unreadable multipart file in request

This is the request headers when calling to /uploadMultipleFiles through Swagger (getting error):

This is the request headers when calling /uploadMultipleFiles from Postman (works fine):

This is the request headers when calling /upload from Postman (works fine):

This is the request headers when calling /upload through Swagger (works fine):

Firstly I thought that Content-Type might have something to do with my problem. But Swagger sends always application/json, and it works with the single upload endpoint.

Any idea?

libanbn · Accepted Answer · 2020-06-05 18:14:54Z

1

When you are dealing with file uploads using multipartfile, you should set the content type of the request to multipart/form-data. The screenshot shows that Postman is using multipart/form-data and not application/json.

answered Jun 5, 2020 at 18:14

libanbn

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2 Comments

ElPiter Over a year ago

Thank you very much for the answer. The question then is: how do I tell Swagger to set the Content-Type to multipart/form-data? And one comment: the last image shows how the single file upload works fine from swagger (setting Content-Type to application/json).

libanbn Over a year ago

If you're using the OAS3 standard in Swagger, you can use this: swagger.io/docs/specification/describing-request-body They use application/json for their example and you can replace that with the content type on the answer. Without looking at the request body, I unfortunately can't say why it works like that with Swagger

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