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How to use fetch to upload files to web api(parameter problem)

My aspnetcore web api side is
[ApiController]
[Route("api/[controller]")]
public class SoundController : ControllerBase
{
[HttpPost]
public async Task<IActionResult> OnPostUploadAsync(List<IFormFile> files0)
{
var files = Request.Form.Files;
.....
return Ok(new { count = files.Count, size });
}
}
My script to post file is as follows:
const blob = new Blob(chunks, { type: "audio/mp3" });
let formData = new FormData();
formData.append("abcd", blob, "a.mp3");
let response = await fetch("api/sound", {
method: 'post',
body: formData
});
if (response.ok) {
var data = await response.json();
console.log(`response.status=${response.status}, data.count==${data.count},
data.size=${data.size}`);
}
My question is:
Although fetch DO reach the OnPostUploadAsync function,
but the parameter files0 is of length 0.
hower inside OnPostUploadAsync function, we can use Request.Form.Files to get the file uploaded by fetch.
what am I wrong? parameter type issue?

read file with php that sent by axios with content-type : image/jpeg [duplicate]

Using raw HTML when I post a file to a flask server using the following I can access files from the flask request global:
<form id="uploadForm" action='upload_file' role="form" method="post" enctype=multipart/form-data>
<input type="file" id="file" name="file">
<input type=submit value=Upload>
</form>
In flask:
def post(self):
if 'file' in request.files:
....
When I try to do the same with Axios the flask request global is empty:
<form id="uploadForm" enctype="multipart/form-data" v-on:change="uploadFile">
<input type="file" id="file" name="file">
</form>
uploadFile: function (event) {
const file = event.target.files[0]
axios.post('upload_file', file, {
headers: {
'Content-Type': 'multipart/form-data'
}
})
}
If I use the same uploadFile function above but remove the headers json from the axios.post method I get in the form key of my flask request object a csv list of string values (file is a .csv).
How can I get a file object sent via axios?

Add the file to a formData object, and set the Content-Type header to multipart/form-data.
var formData = new FormData();
var imagefile = document.querySelector('#file');
formData.append("image", imagefile.files[0]);
axios.post('upload_file', formData, {
headers: {
'Content-Type': 'multipart/form-data'
}
})

Sample application using Vue. Requires a backend server running on localhost to process the request:
var app = new Vue({
el: "#app",
data: {
file: ''
},
methods: {
submitFile() {
let formData = new FormData();
formData.append('file', this.file);
console.log('>> formData >> ', formData);
// You should have a server side REST API
axios.post('http://localhost:8080/restapi/fileupload',
formData, {
headers: {
'Content-Type': 'multipart/form-data'
}
}
).then(function () {
console.log('SUCCESS!!');
})
.catch(function () {
console.log('FAILURE!!');
});
},
handleFileUpload() {
this.file = this.$refs.file.files[0];
console.log('>>>> 1st element in files array >>>> ', this.file);
}
}
});
https://codepen.io/pmarimuthu/pen/MqqaOE

If you don't want to use a FormData object (e.g. your API takes specific content-type signatures and multipart/formdata isn't one of them) then you can do this instead:
uploadFile: function (event) {
const file = event.target.files[0]
axios.post('upload_file', file, {
headers: {
'Content-Type': file.type
}
})
}

Sharing my experience with React & HTML input
Define input field
<input type="file" onChange={onChange} accept ="image/*"/>
Define onChange listener
const onChange = (e) => {
let url = "https://<server-url>/api/upload";
let file = e.target.files[0];
uploadFile(url, file);
};
const uploadFile = (url, file) => {
let formData = new FormData();
formData.append("file", file);
axios.post(url, formData, {
headers: {
"Content-Type": "multipart/form-data",
},
}).then((response) => {
fnSuccess(response);
}).catch((error) => {
fnFail(error);
});
};
const fnSuccess = (response) => {
//Add success handling
};
const fnFail = (error) => {
//Add failed handling
};

This works for me, I hope helps to someone.
var frm = $('#frm');
let formData = new FormData(frm[0]);
axios.post('your-url', formData)
.then(res => {
console.log({res});
}).catch(err => {
console.error({err});
});

this is my way:
var formData = new FormData(formElement);
// formData.append("image", imgFile.files[0]);
const res = await axios.post(
"link-handle",
formData,
{
headers: {
"Content-Type": "multipart/form-data",
},
}
);

How to post file using an object in memory (like a JSON object):
import axios from 'axios';
import * as FormData from 'form-data'
async function sendData(jsonData){
// const payload = JSON.stringify({ hello: 'world'});
const payload = JSON.stringify(jsonData);
const bufferObject = Buffer.from(payload, 'utf-8');
const file = new FormData();
file.append('upload_file', bufferObject, "b.json");
const response = await axios.post(
lovelyURL,
file,
headers: file.getHeaders()
).toPromise();
console.log(response?.data);
}

There is an issue with Axios version 0.25.0 > to 0.27.2 where FormData object in a PUT request is not handled correctly if you have appended more than one field but is fine with one field containing a file, POST works fine.
Also Axios 0.25.0+ automatically sets the correct headers so there is no need to specify Content-Type.

For me the error was the actual parameter name in my controller... Took me a while to figure out, perhaps it will help someone. Im using Next.js / .Net 6
Client:
export const test = async (event: any) => {
const token = useAuthStore.getState().token;
console.log(event + 'the event')
if (token) {
const formData = new FormData();
formData.append("img", event);
const res = await axios.post(baseUrl + '/products/uploadproductimage', formData, {
headers: {
'Authorization': `bearer ${token}`
}
})
return res
}
return null
}
Server:
[HttpPost("uploadproductimage")]
public async Task<ActionResult> UploadProductImage([FromForm] IFormFile image)
{
return Ok();
}
Error here because server is expecting param "image" and not "img:
formData.append("img", event);
public async Task<ActionResult> UploadProductImage([FromForm] IFormFile image)

Nest Js file upload not working with javascript FormData

I have some issues parsing a request made from the front-end using FormData. This is the example request generated from Postman for node.js Axios. If I use the postman app with the request, it works as expected.
Frontend example generated from Postman code feature.
var axios = require('axios');
var FormData = require('form-data');
var fs = require('fs');
var data = new FormData();
data.append('file', fs.createReadStream('/some_file.jpg')); **//I am using Electron and I have acces to the FileSystem from the client.**
data.append('resizeLargeImage[width]', '1920');
data.append('resizeLargeImage[height]', '1080');
data.append('resizeLargeImage[type]', 'cover');
var config = {
method: 'post',
url: 'localhost:3030/api/v1/optimize-single',
headers: {
'x-api-key': '123',
...data.getHeaders()
},
data : data
};
axios(config)
.then(function (response) {
console.log(JSON.stringify(response.data));
})
.catch(function (error) {
console.log(error);
});
Backend
#Post('/optimize-single')
#UseInterceptors(FileInterceptor('file'))
async uploadFile(
#UploadedFile() file: FileDto,
#Body() body: UploadFileParametersDto,
#Res() response: Response,
): Promise<any> {
console.log('file', file, 'body', body);
**//File is undefined, body is a null Object**
return await this.appService.uploadFile(file, body, response);
}
Any ideas as to why Nest doesn't recognize this type of request?
Thanks!

I managed to figure it out.
If you are in the Renderer process, it works by attaching the file as a blob.
const fileBuffer = fs.readFileSync(filePath);
const fileName = path.basename(filePath);
const blob = new Blob([fileBuffer], {
type: mime.lookup(filePath),
});
formData.append('file', blob, fileName);
If you move the same functionality in the Main process it will work as expected with data.append('file', fs.createReadStream('/some_file.jpg'));

React ajax request with multipart file and json data

I have a base request like this:
export const request = (options) => {
const headers = new Headers({
'Content-Type': 'application/json',
});
if (Common.getToken()) {
headers.append('Authorization', 'Bearer ' + Common.getToken())
}
const defaults = {headers: headers};
options = Object.assign({}, defaults, options);
return fetch(options.url, options)
.then(response =>
response.json().then(json => {
if (!response.ok) {
return Promise.reject(json);
}
return json;
})
);
};
and my ajax request:
onCreateNewPost(postDataRequest, photoBody) {
const formData = new FormData();
formData.append('photo', photoBody);
formData.append('postData', JSON.stringify(postDataRequest));
return request({
url: API_BASE_URL + '/posts/new-post',
method: 'POST',
body: formData
});
};
where postDataRequest - json object included post title, description etc...
photoBody - image file.
In the backend I have a controller's method:
#PostMapping(value = "/api/posts/new-post")
#PreAuthorize("hasRole('ADMIN')")
public ResponseEntity createNewPost(#CurrentUser UserPrincipal currentUser,
#RequestBody NewPostDataRequest postRequest,
#RequestParam MultipartFile photo) {
// method body
return ResponseEntity.ok(new ActionCompleteResponse(true));
}
but when I send a request, I get Status Code: 400. What is the problem? I can separately send either json data or multipart data, but I can’t figure out how to transfer them together with one request. I tried to put headers without a Content-Type in the request, as in the code below, so that the request itself indicates it, but in response I get code 415.
onCreateNewPost(postDataRequest, photoBody) {
const formData = new FormData();
formData.append('photo', photoBody);
formData.append('postData', JSON.stringify(postDataRequest));
const headers = new Headers({});
if (Common.getToken()) {
headers.append('Authorization', 'Bearer ' + Common.getToken());
}
return request({
url: API_BASE_URL + '/posts/new-post',
headers: headers,
method: 'POST',
body: formData
});
};
What should I do?

Okay, I found the solution:
1. Clear headers data (except Authorization token)
2. Add to #PostMapping consumes = MediaType.MULTIPART_FORM_DATA_VALUE and add #RequestPart to method parameter
ajax request like:
onCreateNewPost(postDataRequest, photoBody) {
const formData = new FormData();
formData.append('post', new Blob([JSON.stringify(postDataRequest)], {
type: "application/json"
}));
formData.append('photo', photoBody);
const headers = new Headers({});
if (Common.getToken()) {
headers.append('Authorization', 'Bearer ' + Common.getToken())
}
return request({
url: API_BASE_URL + '/posts/new-post',
method: 'POST',
headers: headers,
body: formData
});
};
and spring controller like
#PostMapping(value = "/new-post", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
#PreAuthorize("hasRole('USER')")
public ResponseEntity createNewPost(#CurrentUser UserPrincipal currentUser,
#RequestPart("post") #Valid PostEntity post,
#RequestPart("photo") #Valid MultipartFile photo) throws IOException {
post.setAuthor(currentUser.getUsername());
post.setAuthorId(currentUser.getId());
post.setCommentsCount(0L);
post.setDate(LocalDate.now());
post.setPhoto(photo.getBytes());
postService.save(post);
return ResponseEntity.ok(new ActionCompleteResponse(true));
}

#Sergey Scream solution is correct, I just want to add some information to clarify the problem.
So if you want to send json and a file using FormData you have to wrap your json in a blob including the type like he did:
formData.append('post', new Blob([JSON.stringify(postDataRequest)], {
type: "application/json"
}));
Adding your json like this will not work:
formData.append('post', JSON.stringify(postDataRequest));

You're setting Content-Type to application/json in request but body to form data in onCreateNewPost. If you removed line 3 from request then your current solution should work.
Also you're setting the Authorization header twice in onCreateNewPost and request.

Send Image file along with other data to Java backend using React.JS

I want to send an uploaded image file along with data entered by the user to the backend which is implemented on JAVA.
`const payload = {
id: null,
name : Name,
email : Email
};
//data.append("myjsonkey", );
await fetch('http://localhost:8080/student/insertStudent', {
method: 'POST',
body: JSON.stringify(payload),
headers : {
'Accept': 'application/json',
'Content-Type': 'application/json'
}
})`
Using this implementation I was able to send data to backend using POST request. I now want to attach an image file in the payload to be recieved at the backend.
The Code written for the image uploading is
`fileChangedHandler = (event) => {
this.setState({selectedFile: event.target.files[0]})
}
uploadHandler = () => {
console.log(this.state.selectedFile)
}
render() {
return (
<div>
<input type="file" onChange={this.fileChangedHandler}/>
<button onClick={this.uploadHandler}>Upload!</button>
</div>
);
}`
Any help will be highly appreciated.

You can send data using formData... here is the sample code for api request in react.
uploadHandler = () => {
const formData = new FormData();
formData.append('file', this.state.selectedFile);
axios.post('http://localhost:8080/student/image',
formData
);
}
Java controller
#CrossOrigin(origins = "http://localhost:3000")
#RestController
#RequestMapping("/student/")
public class StudentController {
#RequestMapping(value = "image" ,method = RequestMethod.POST, consumes = "multipart/form-data")
#ResponseStatus(HttpStatus.CREATED)
public void image(
#RequestParam("file") MultipartFile file ){
// CODE HERE
}
}