I am trying to upload an image to an S3 bucket using a presigned URL generated using boto3 on Python. I have been using the example python code that was provided in the documentation and was successful (the image got correctly uploaded with the correct Content-Type). However, when trying to do this in Javascript for the purposes of our frontend application, I am really struggling to get it to work.
Here's the example dictionary returned by the backend:
{
"fields": {
"AWSAccessKeyId": "AKIAYS3VM3EBIFL7FKE5",
"key": "posts/623255a762fd9bdfbd13f91a",
"policy": "<very long string>",
"signature": "Qvc/sGBHk0uzirzIfR1YmE2kFlo="
},
"url": "https://hotspot-storage.s3.amazonaws.com/"
}
Here is the functioning Python code:
response = <json response object>
object_name = 'playground/example_profile_group.png'
response['fields']['Content-Type'] = "image/png"
# Demonstrate how another Python program can use the presigned URL to upload a file
with open(object_name, 'rb') as f:
files = {'file': (object_name, f)}
http_response = requests.post(response['url'], data=response['fields'], files=files)
# If successful, returns HTTP status code 204
print(http_response)
print(http_response.text)
Here is the non-functioning Javascript code:
const data = response.data;
let payload = data.fields;
payload['Content-Type'] = 'image/jpeg';
const file = {
uri: previewPath,
name: previewPath,
type: 'image/jpeg',
};
payload.file = file;
const url = data.url;
console.log(payload, "MY PAYLOAD")
axios({
method: 'post',
headers: {'Content-Type': 'multipart/form-data'},
url: url,
data: payload,
})
.then(function (response) {
console.log(response.data, 'uploaded');
const data = response.data;
})
.catch(function (error) {
console.log(
'error uploading image',
error.response.data,
);
});
})
.catch(function (error) {
console.log(
'error getting media link',
error.response.data,
);
});
This is the error that keeps getting returned:
error uploading image <?xml version="1.0" encoding="UTF-8"?>
<Error><Code>MalformedPOSTRequest</Code><Message>The body of your POST request is not well-formed multipart/form-data.</Message><RequestId>Q0ES6P4QP75YVVED</RequestId><HostId>eowLxSJQD1xP1EfHPnzGSJzXVGpPjurIMhkdwAD22JMvi9zRoFGg6Bq+mnUt/Lu7DNPY80iBDMc=</HostId></Error>
I have been stuck on this for an absurd amount of time, and cannot tell what I am doing wrong. Any help would be very much appreciated.
In order to send a multipart/form-data request body, you'll need to use a FormData instance instead of a JavaScript object.
For example
const { url, fields } = response.data;
const payload = new FormData();
payload.append("file", file); // this is the file blob, eg from <input type="file">
payload.append("Content-Type", "image/jpeg");
// add all the other fields
Object.entries(fields).forEach(([ key, val ]) => {
payload.append(key, val);
});
// No need to manually set content-type header, your browser knows what to do
const { data: result } = await axios.post(url, payload);
console.log("uploaded", result);