Скачать или смотреть How to Handle Async Token Refresh in Angular Interceptors Using RxJS

Learn how to effectively manage asynchronous operations in Angular HTTP interceptors for token refresh scenarios with RxJS.
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This video is based on the question https://stackoverflow.com/q/72115777/ asked by the user 'Georgian Stan' ( https://stackoverflow.com/u/11152509/ ) and on the answer https://stackoverflow.com/a/72116362/ provided by the user 'Mahdi Rezazadeh' ( https://stackoverflow.com/u/8554578/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Manage Async Token Refresh in Angular Interceptors

When developing applications with Angular, managing user authentication and token refresh can sometimes lead to complex issues. One particular problem is how to handle asynchronous operations, like fetching a new token, within an HTTP interceptor. In this post, we'll explore this problem and provide a detailed solution to implement a seamless token refresh mechanism in Angular.

Understanding the Problem: Async Token Refresh

Imagine you have an Angular interceptor designed to manage API requests. This interceptor checks for authentication errors (HTTP 401 status) and attempts to retrieve a new access token if needed. The challenge arises when the method responsible for fetching the new token is asynchronous. Attempting to use an async function directly in a reactive operation can lead to TypeScript errors or runtime exceptions.

Here’s the key requirement:

The token refresh operation needs to be handled using an observable pattern rather than asynchronous functions.

The Original Code Challenge

The initial attempt used the async/await syntax, which is not suitable within an RxJS operator like catchError. Here’s a snippet of the original implementation for better context:

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The Errors Encountered

TypeScript threw an error indicating that the return type was not assignable due to incompatibility between observables and promises. Besides, when bypassing the TypeScript errors, runtime exceptions like EmptyError: no elements in sequence were observed, rendering the app inoperable.

The Solution: Using Observables for Async Operations

To resolve the issue of handling an asynchronous token refresh within an Angular interceptor, we can adopt an observable-based approach. Here's how to implement that.

Step 1: Modify the Interceptor

Instead of trying to handle async operations directly within the interceptor's catchError, create a separate method to refresh the token. Here’s the modified interceptor code:

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Step 2: Implement the Token Refresh Logic

Next, we define the handleUnauthorized method that manages token refresh operations. Here’s how you can implement this method:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Update AuthService for Token Management

Finally, adjust your authService to manage the token state properly, which includes setting and getting the token as observable:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following this approach, you can effectively manage asynchronous token refresh in Angular interceptors using RxJS. This structure allows for handling multiple requests and ensures that the application can continue to operate smoothly, even when a token refresh is in progress.

Feel free to ask questions or seek clarifications in the comments section below. Happy coding!