Sending Data from React to MySQL - mysql

Question

I am creating a publishing application that needs to use communication between React and MySQL database to send information back and forth. Using Express as my JS server. The server code looks as follows:
const express = require('express');
const bodyParser = require('body-parser');
const mysql = require('mysql');
const cors = require('cors');
const connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : '',
database : 'ArticleDatabase',
port: 3300,
socketPath: '/Applications/XAMPP/xamppfiles/var/mysql/mysql.sock'
});
// Initialize the app
const app = express();
app.use(cors());
appl.post('/articletest', function(req, res) {
var art = req.body;
var query = connection.query("INSERT INTO articles SET ?", art,
function(err, res) {
})
})
// https://expressjs.com/en/guide/routing.html
app.get('/comments', function (req, res) {
// connection.connect();
connection.query('SELECT * FROM articles', function (error, results,
fields) {
if (error) throw error;
else {
return res.json({
data: results
})
};
});
// connection.end();
});
// Start the server
app.listen(3300, () => {
console.log('Listening on port 3300');
});
And my React class looks as follows:
class Profile extends React.Component {
constructor(props) {
super(props);
this.state = {
title: '',
author: '',
text: ''
}
}
handleSubmit() {
// On submit of the form, send a POST request with the data to the
// server.
fetch('http://localhost:3300/articletest', {
body: JSON.stringify(this.state),
cache: 'no-cache',
credentials: 'same-origin',
headers: {
'content-type': 'application/json'
},
method: 'POST',
mode: 'cors',
redirect: 'follow',
referrer: 'no-referrer',
})
.then(function (response) {
console.log(response);
if (response.status === 200) {
alert('Saved');
} else {
alert('Issues saving');
}
});
}
render() {
return (
<div>
<form onSubmit={() => this.handleSubmit()}>
<input type = "text" placeholder="title" onChange={e =>
this.setState({ title: e.target.value} )} />
<input type="text" placeholder="author" onChange={e =>
this.setState({ author: e.target.value} )} />
<textarea type="text" placeholder="text" onChange={e =>
this.setState({ text: e.target.value} )} />
<input type="Submit" />
</form>
</div>
);
}
}
So fairly standard stuff that I found in online tutorials. I can search my database and display fetched info no problem, but not the other way around. When I try to take input from the <form> tag nothing is inserted into my database but instead I get this error:
[Error] Fetch API cannot load
http://localhost:3000/static/js/0.chunk.js due to access control
checks.
Error: The error you provided does not contain a stack trace.
Unhandled Promise Rejection: TypeError: cancelled
I understand that this has something to do with access control but since I am already using cors and can successfully retrieve data from the database, I am not sure what I am doing wrong. Any suggestions will be greatly appreciated. Thank you in advance.

Answer 1

You'll need to isolate the problem by first verifying that your service point is CORS Enabled. In order to focus solely on CORS functionality, I would remove the MySQL code temporarily.
const express = require('express');
const bodyParser = require('body-parser');
const cors = require('cors');
const app = express();
app.use(cors());
app.get('/', function(req, res){
var root = {};
root.status = 'success';
root.method = 'index';
var json = JSON.stringify(root);
res.send(json);
});
app.post('/cors', function(req, res) {
var root = {};
root.status = 'success';
root.method = 'cors';
var json = JSON.stringify(root);
res.send(json);
})
// Start the server
app.listen(3300, () => {
console.log('Listening on port 3300');
});
One you have server listening on port 3300, run the following PREFLIGHT command at the terminal.
curl -v \
-H "Origin: https://example.com" \
-H "Access-Control-Request-Headers: X-Custom-Header" \
-H "Acess-Control-Request-Method: POST" \
-X OPTIONS \
http://localhost:3300
If the preflight request is successful, the response should include Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers
Now run the POST method.
curl -v \
-H "Origin: https://example.com" \
-H "X-Custom-Header: value" \
-X POST \
http://localhost:3300/cors
If the post request is successful, the response should include
Access-Control-Allow-Origin
If everything looks good, your server is okay. You then need to try the post method from your iOS app.
NOTE. I would also be suspicious of using cors on localhost. I would map 127.0.0.1 to a domain and then have the app use that domain instead. If you are on Linux or Mac, you modify /etc/hosts. For Windows it's c:\windows\system32\drivers\etc\hosts

Answer 2

Try explicitly whitelisting the server that is making the request:
const whitelist = ['http://localhost:3000']; // React app
const corsInstance = cors({
origin: (origin, callback) => {
if (!origin || whitelist.indexOf(origin) !== -1) {
callback(null, true);
} else {
callback(new Error('Not allowed by CORS'));
}
}
});
application.use(corsInstance);
https://expressjs.com/en/resources/middleware/cors.html#configuring-cors-w-dynamic-origin

Answer 3

You need to add event.preventDefault() at the end of your handleSubmit method (check this example https://stackblitz.com/edit/react-forms).
You have to do it for the reason for preventing form default behavior on submit: it tries to synchronously send data to the url it loaded from (since there is no action attribute on it).

Answer 4

For those who may have run into a similar problem, I was able to fix it by dumping express server altogether. I simply used the .php file on the Apache server to insert data into database. Hope it helps somebody.