Part 65: Building a Robust Login API Route in Next.js: Handling Authentication and User Data

[Pages] Authentication

[Pages] Authentication

In our journey to create a secure and efficient login system, we've established a foundational API route that accepts user credentials and communicates with a CMS to authenticate users. In this post, we'll delve into how we can refine this API route to handle user data more effectively and manage authentication errors gracefully.

Handling User Credentials and Communicating with the CMS

When a user submits their login information, our API route must forward these credentials to the CMS for verification. Let's explore how we can implement this flow.

Step 1: Extracting User Credentials

First, we need to extract the email and password from the request body. This information is crucial for authenticating the user with the CMS.

Step 2: Communicating with the CMS

To authenticate the user, we'll send a POST request to the CMS's authentication endpoint. This process involves using a utility function, fetchJson, which simplifies fetching and handling JSON data.

Here's how we can integrate this into our API route:

// pages/api/login.js

import { fetchJson } from '../../lib/api';

async function handleLogin(req, res) {
  if (req.method !== 'POST') {
    res.status(405).end(); // Method Not Allowed
    return;
  }

  const { email, password } = req.body;

  try {
    const { jwt, user } = await fetchJson('http://localhost:1337/auth/local', {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ identifier: email, password }),
    });

    // TODO: Set jwt cookie

    res.status(200).json({
      id: user.id,
      name: user.username,
    });
  } catch (err) {
    res.status(401).end(); // Unauthorized
  }
}

export default handleLogin;

Explanation:

• Async Function: The handleLogin function is asynchronous to handle the promise returned by fetchJson.

• CMS Request: We send the credentials to the CMS authentication endpoint. If successful, the CMS returns a JWT and user details.

• Response Handling: We extract the jwt and user from the CMS response. While we plan to set the JWT as a cookie later, we return selected user details (id and name) in the response.

Handling Errors Gracefully

A critical aspect of building robust applications is error handling. If the user provides incorrect credentials, we need to respond appropriately.

Error Handling Strategy

In our API route, we catch any errors thrown during the CMS request. If authentication fails due to incorrect credentials, we return a 401 Unauthorized response.

• Unauthorized Access: A 401 status code indicates that the request lacks valid authentication credentials.

• Distinguishing Errors: Although we treat all errors uniformly here, it's advisable to differentiate between authentication errors and network issues for better error management.

Testing the API Route

When testing our API route:

• Successful Login: A POST request with valid credentials should return user details with a 200 OK status.

• Invalid Credentials: If the credentials are incorrect, the response should be 401 Unauthorized.

Conclusion

We've successfully constructed a Next.js API route that handles user login by communicating with a CMS, extracting user details, and managing errors. In future enhancements, we'll focus on securely storing the JWT as a cookie, ensuring persistent authentication while maintaining security. By implementing these practices, we ensure that our application is both user-friendly and secure.

Stay tuned for more insights as we continue to build and refine this authentication system!