Custom Spotify Code Keychain: How to Implement Automatic Token Refresh in Your Flutter App

When building a mobile app that interacts with the Spotify API, it's crucial to implement automatic token refresh to ensure uninterrupted service and prevent token expiration issues. In this article, we'll explore how to achieve this in your Flutter app using the Spotify SDK.

How Does Token Refresh Work?

By default, the Mobile SDK for iOS, Mobile SDK for Android, Amplify for iOS, Android, and Flutter automatically refresh ID and access tokens if a valid (unexpired) refresh token is present. This means that when you use these SDKs in your app, they will handle token refresh for you without requiring manual intervention.

Implementing Token Refresh in Your Flutter App

To implement automatic token refresh in your Flutter app, you can follow these steps:

1. Obtain a Refresh Token: When you initialize the Spotify SDK in your Flutter app, make sure to obtain a refresh token along with an access token. You can do this by providing the necessary credentials and redirect URI.

2. Store the Refresh Token Securely: Store the obtained refresh token securely using a package like `flutter_secure_storage`. This will ensure that it's not accessible to unauthorized parties.

3. Create a Token Interceptor: Create a custom token interceptor that will handle token refresh when an access token expires. You can use a package like `http` to create a middleware that intercepts HTTP requests and checks if the access token has expired.

4. Refresh the Access Token: If the access token has expired, use the stored refresh token to obtain a new access token. You can do this by making a request to the Spotify API's token endpoint with the refresh token and client ID.

5. Update the HTTP Client: Update your HTTP client to use the newly obtained access token for subsequent requests.

Example Code

Here's an example of how you can implement a token interceptor in your Flutter app:

```dart

import 'package:http/http.dart' as http;

import 'package:flutter_secure_storage/flutter_secure_storage.dart';

class TokenInterceptor with http.Interceptor {

final storage = FlutterSecureStorage();

@override

Future intercept(http.Request request) async {

// Check if the access token has expired

String accessToken = await storage.read(key: 'access_token');

DateTime expirationTime = DateTime.parse(accessToken.split('.')'2');

if (expirationTime.isBefore(DateTime.now())) {

// Refresh the access token using the refresh token

String refreshToken = await storage.read(key: 'refresh_token');

http.Response response = await http.post(

Uri.parse('https://accounts.spotify.com/api/token'),

headers: {

'Content-Type': 'application/x-www-form-urlencoded',

body: 'grant_type=refresh_token&refresh_token=$refreshToken',

);

if (response.statusCode == 200) {

// Store the new access token

await storage.write(key: 'access_token', value: response.json()''access_token'');

} else {

// Handle error

}

// Update the HTTP client with the new access token

request.headers''Authorization'' = 'Bearer ${await storage.read(key: 'access_token')}';

return http.StreamedResponse.fromFuture(request.send());

}

```

In this article, we've explored how to implement automatic token refresh in your Flutter app using the Spotify SDK. By following these steps and implementing a custom token interceptor, you can ensure that your app continues to function seamlessly without interruptions due to token expiration.

Custom spotify code keychain