request得到域名的方法

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  const host = req.headers.host;
  res.send(`Host: ${host}`);
});

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

from flask import Flask, request

app = Flask(__name__)

@app.route('/')
def index():
    host = request.headers.get('Host')
    return f'Host: {host}'

if __name__ == '__main__':
    app.run(port=3000)

<?php
$host = $_SERVER['HTTP_HOST'];
echo "Host: " . $host;
?>

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HostController {

    @GetMapping("/")
    public String getHost() {
        return "Host: " + request.getHeader("Host");
    }
}