Spring boot Multipart file upload using Client Side Java Code

Question

I have written a restful web service in spring boot which receives the file.

@RequestMapping(value = "/upload", method = RequestMethod.POST)
@ResponseBody
public void uploadFile(@RequestParam("file") MultipartFile uploadfile) {
    System.out.println("filename: " + uploadfile.getName());
}

How can we upload the file from client side java code to web service. Instead of AJAX call or HTML page form multipart request?

The code below call the web service with JSON object. Like this I want to receive the file in above written web service.

void clientRequest(String server_url, JSONObject fileObj){

  try {

    URL url = new URL(server_url);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setDoOutput(true);
    conn.setRequestMethod("POST");
    conn.setRequestProperty("Content-Type", "application/json");

    OutputStream os = conn.getOutputStream();
    os.write(fileObj.toString().getBytes());
    os.flush();

    BufferedReader br = new BufferedReader(new InputStreamReader(
            (conn.getInputStream())));

    String output;
    System.out.println("Output from Server .... \n");
    while ((output = br.readLine()) != null) {
        logger.info("output :: " + output);
    }

    conn.disconnect();

  } catch (Exception e) {
    e.printStackTrace();
  }
}

Darshan Mehta · Accepted Answer · 2017-02-09 19:38:39Z

1

You can use Spring's HttpEntity along with ByteArrayResource to upload the file, here is an example:

MultiValueMap<String, Object> data = new LinkedMultiValueMap<String, Object>();
ByteArrayResource resource = new ByteArrayResource(file.getBytes()) {
    @Override
    public String getFilename() {
        return file.getName();
    }
};
data.add("file", resource);

HttpHeaders requestHeaders = new HttpHeaders();
requestHeaders.setContentType(MediaType.MULTIPART_FORM_DATA);

HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<MultiValueMap<String, Object>>(data, requestHeaders);

final ResponseEntity<<SomeClass>> responseEntity = restTemplate.exchange(<url>, 
        HttpMethod.POST, requestEntity, new ParameterizedTypeReference<SomeClass>(){});

SomeClass result = responseEntity.getBody();

answered Feb 9, 2017 at 19:38

Darshan Mehta

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Community · Accepted Answer · 2017-05-23 11:46:25Z

0

If you want to use a MultipartFile, you must use the multipart/form-data mimetype when requesting. Instead of sending the JSON as request entity, you should construct a specific multipart-entity with a single field file in it.

This is how it's done: How can I make a multipart/form-data POST request using Java?

edited May 23, 2017 at 11:46

CommunityBot

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answered Feb 9, 2017 at 19:31

Frederik Heremans

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5 Comments

Kunal Utage Over a year ago

The code given in the link is not working. I have already tired it. Most of it's methods are deprecated.

Frederik Heremans Over a year ago

The code contains an updated answer for the 4.3 version of http-client.

Kunal Utage Over a year ago

Thanks I tired http-client 4.3 It's working earlier it wasn't working

Kunal Utage Over a year ago

How can we send JSONObject along with the file to web service

Frederik Heremans Over a year ago

You can include the JSON as a second multipart form field with another field name. You'll get a second @RequestParam in the REST controller. Just pull that file stream throug an ObjectMapper. Because you're using multipart miletype, you cant use the @RequestBody to get the JSON converted to a POJO. If the JSON data you want to combine with the file is really simple, consider flattening the data and include it as separate form-fields which contain the property values istead of a file...

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