如何在Express.js中设置身份验证中间件

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

// 假设这是你的JWT密钥
const JWT_SECRET = 'your_jwt_secret';

// 中间件：验证JWT令牌
function authenticateToken(req, res, next) {
  const authHeader = req.headers['authorization'];
  const token = authHeader && authHeader.split(' ')[1];

  if (token == null) return res.sendStatus(401);

  jwt.verify(token, JWT_SECRET, (err, user) => {
    if (err) return res.sendStatus(403);
    req.user = user;
    next();
  });
}

// 受保护的路由
app.get('/protected', authenticateToken, (req, res) => {
  res.send(`Hello, ${req.user.username}! This is a protected route.`);
});

// 启动服务器
app.listen(3000, () => {
  console.log('Server is running on port 3000');
});