We want to send an image file as multipart/form to the backend, we try to use html form to get file and send the file as formData, here are the codes
export default class Task extends React.Component {
uploadAction() {
var data = new FormData();
var imagedata = document.querySelector('input[type="file"]').files[0];
data.append("data", imagedata);
fetch("http://localhost:8910/taskCreationController/createStoryTask", {
mode: 'no-cors',
method: "POST",
headers: {
"Content-Type": "multipart/form-data"
"Accept": "application/json",
"type": "formData"
},
body: data
}).then(function (res) {
if (res.ok) {
alert("Perfect! ");
} else if (res.status == 401) {
alert("Oops! ");
}
}, function (e) {
alert("Error submitting form!");
});
}
render() {
return (
<form encType="multipart/form-data" action="">
<input type="file" name="fileName" defaultValue="fileName"></input>
<input type="button" value="upload" onClick={this.uploadAction.bind(this)}></input>
</form>
)
}
}
The error in backend is "nested exception is org.springframework.web.multipart.MultipartException: Could not parse multipart servlet request; nested exception is java.io.IOException: org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found".
After reading this, we tried to set boundary to headers in fetch:
fetch("http://localhost:8910/taskCreationController/createStoryTask", {
mode: 'no-cors',
method: "POST",
headers: {
"Content-Type": "multipart/form-data; boundary=AaB03x" +
"--AaB03x" +
"Content-Disposition: file" +
"Content-Type: png" +
"Content-Transfer-Encoding: binary" +
"...data... " +
"--AaB03x--",
"Accept": "application/json",
"type": "formData"
},
body: data
}).then(function (res) {
if (res.ok) {
alert("Perfect! ");
} else if (res.status == 401) {
alert("Oops! ");
}
}, function (e) {
alert("Error submitting form!");
});
}
This time, the error in backend is: Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
Do we add the multipart boundary right? Where should it be? Maybe we are wrong at first because we don't get the multipart/form-data. How can we get it correctly?
We just try to remove our headers and it works!
fetch("http://localhost:8910/taskCreationController/createStoryTask", {
mode: 'no-cors',
method: "POST",
body: data
}).then(function (res) {
if (res.ok) {
alert("Perfect! ");
} else if (res.status == 401) {
alert("Oops! ");
}
}, function (e) {
alert("Error submitting form!");
});
Here is my solution for image upload with preview through axios.
import React, { Component } from 'react';
import axios from "axios";
React Component Class:
class FileUpload extends Component {
// API Endpoints
custom_file_upload_url = `YOUR_API_ENDPOINT_SHOULD_GOES_HERE`;
constructor(props) {
super(props);
this.state = {
image_file: null,
image_preview: '',
}
}
// Image Preview Handler
handleImagePreview = (e) => {
let image_as_base64 = URL.createObjectURL(e.target.files[0])
let image_as_files = e.target.files[0];
this.setState({
image_preview: image_as_base64,
image_file: image_as_files,
})
}
// Image/File Submit Handler
handleSubmitFile = () => {
if (this.state.image_file !== null){
let formData = new FormData();
formData.append('customFile', this.state.image_file);
// the image field name should be similar to your api endpoint field name
// in my case here the field name is customFile
axios.post(
this.custom_file_upload_url,
formData,
{
headers: {
"Authorization": "YOUR_API_AUTHORIZATION_KEY_SHOULD_GOES_HERE_IF_HAVE",
"Content-type": "multipart/form-data",
},
}
)
.then(res => {
console.log(`Success` + res.data);
})
.catch(err => {
console.log(err);
})
}
}
// render from here
render() {
return (
<div>
{/* image preview */}
<img src={this.state.image_preview} alt="image preview"/>
{/* image input field */}
<input
type="file"
onChange={this.handleImagePreview}
/>
<label>Upload file</label>
<input type="submit" onClick={this.handleSubmitFile} value="Submit"/>
</div>
);
}
}
export default FileUpload;
The file is also available in the event:
e.target.files[0]
(eliminates the need for document.querySelector('input[type="file"]').files[0];)
uploadAction(e) {
const data = new FormData();
const imagedata = e.target.files[0];
data.append('inputname', imagedata);
...
Note:
Use console.log(data.get('inputname')) for debugging, console.log(data) will not display the appended data.