Middleware Nâng cao và Error Handling

Custom Middleware

Logging Middleware

const logger = (req, res, next) => {
  console.log(`${new Date().toISOString()} - ${req.method} ${req.url}`);
  next();
};

app.use(logger);

Authentication Middleware

const authenticate = (req, res, next) => {
  const token = req.headers.authorization?.replace('Bearer ', '');
  
  if (!token) {
    return res.status(401).json({ error: 'No token provided' });
  }

  try {
    const decoded = jwt.verify(token, process.env.JWT_SECRET);
    req.user = decoded;
    next();
  } catch (error) {
    return res.status(401).json({ error: 'Invalid token' });
  }
};

app.get('/profile', authenticate, (req, res) => {
  res.json({ user: req.user });
});

Error Handling Middleware

Custom Error Class

class AppError extends Error {
  constructor(message, statusCode) {
    super(message);
    this.statusCode = statusCode;
    this.isOperational = true;
    Error.captureStackTrace(this, this.constructor);
  }
}

Global Error Handler

const errorHandler = (err, req, res, next) => {
  err.statusCode = err.statusCode || 500;
  err.status = err.status || 'error';

  if (process.env.NODE_ENV === 'development') {
    res.status(err.statusCode).json({
      status: err.status,
      error: err,
      message: err.message,
      stack: err.stack
    });
  } else {
    // Production
    if (err.isOperational) {
      res.status(err.statusCode).json({
        status: err.status,
        message: err.message
      });
    } else {
      console.error('ERROR 💥', err);
      res.status(500).json({
        status: 'error',
        message: 'Something went wrong!'
      });
    }
  }
};

app.use(errorHandler);

Async Error Handling

Async Wrapper

const asyncHandler = (fn) => (req, res, next) => {
  Promise.resolve(fn(req, res, next)).catch(next);
};

// Usage
app.get('/users', asyncHandler(async (req, res) => {
  const users = await User.find();
  res.json(users);
}));

Bài tập thực hành

Hãy triển khai error handling cho REST API!