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?
v-on:change="uploadFile"
with input
instead of form
tag ?
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
}
})
}
PUT
to upload file then you may use application/octet-stream
as Content-Type
. If you upload into Amazon S3 storage using multipart/formdata
as Content-Type
it will make your files (images, pdfs, documents) into text files with http header added on top. This will damage the content of the uploaded file. So use application/octet-stream
when uploading binary files with PUT
methods.
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});
});
headers: { 'Content-Type': 'multipart/form-data' }
was the only way it would actually send the post after getting a server response from options. I am probably doing something wrong, but it is working and I'm leaving it alone lol
Content-Type
headers are set automagically. You are supposed to have those undefined.
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
};
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);
}
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)
Success story sharing
FormData
. According to axios's doc, bothFile
andFormData
are treated as Browser only, so both ways can be seen equally (github.com/axios/axios#request-config)data:formData
formData.getHeaders()
This is a known issue with axios; see for e.g.https://github.com/axios/axios/issues/789
File
vs.FormData
: correct me if I'm wrong, but I believeFile
can be used only if you're uploading a single file and not including any other payload data in the request (like in the answer), butFormData
is what you'll have to use if you want to submit a collection of data (that is, a form with several fields) in addition to the file(s) (which I suspect is more often the case in real applications).