Скачать или смотреть Resolving the HttpErrorResponse Issue with Angular and .NET Backend

Discover how to properly handle `403 Forbidden` responses in Angular's HttpClient when working with a .NET backend. Learn to resolve issues and propagate errors effectively!
---
This video is based on the question https://stackoverflow.com/q/68771172/ asked by the user 'Goran' ( https://stackoverflow.com/u/953683/ ) and on the answer https://stackoverflow.com/a/68771271/ provided by the user 'Octavian Mărculescu' ( https://stackoverflow.com/u/1440005/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Problem getting HttpErrorResponse from httpClient

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Dealing with HttpErrorResponse in Angular Armed with a .NET Backend

When working with Angular and a .NET backend, you may encounter a scenario where your application doesn't receive the expected HttpErrorResponse when a user operates on an unauthorized action. This guide offers a detailed explanation of the problem and provides a solution that aims to help restore proper error handling in your application.

The Problem: Unexpected Behavior on 403 Forbidden

In your Angular application, you intend to return an HTTP status of 403 Forbidden from your backend when a user tries to perform an operation they are not allowed to. But you are facing an issue: instead of getting a proper HttpErrorResponse, Angular’s HttpClient throws a TypeError.

Here's a snapshot of the issue:

The backend .NET controller correctly returns Forbid(); for insufficient permissions.

Your Angular service is set to observe responses and handle errors.

However, when the backend responds with a 403, a TypeError: Cannot read property 'message' of null gets logged instead of the expected HttpErrorResponse.

Investigating the Issue

Upon further investigation, it turns out the problem lies within an error.interceptor in your Angular application. Interceptors are used to manage request and response transformations, and in this case, the error thrown by Angular's HttpClient suggests that the interceptor is not handling the response correctly.

Solution: Adjusting the Error Handling

To handle HTTP errors appropriately, including those with status code 403, consider making the following adjustments:

Step 1: Modify the Backend Response

If you want to ensure that your front-end properly interprets the 403 Forbidden response, change your backend code to return an object with a message. For example:

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

This change won't directly resolve the HttpErrorResponse issue but will help you send more informative messages with your responses.

Step 2: Check Your Interceptor

Regarding the TypeError you are encountering, it is crucial to inspect your error.interceptor file, particularly around line 20, where the error is thrown. The interceptor may not be correctly extracting error information due to incorrectly handled response objects.

Make sure that your interceptor follows this pattern:

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

Step 3: Properly Handle Errors in Your Service and Component

Ensure that your Angular service and component handle responses and errors correctly. Here's a refresher on how your components should look:

Service

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

Component

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

Conclusion

Managing HTTP status codes effectively between your Angular front-end and .NET backend can be tricky. However, by ensuring that your interceptor handles errors correctly and returns informative messages, you can effectively propagate errors from the backend to your Angular application.

By following the steps outlined in this post, you should be able to achieve the desired behavior, handling HttpErrorResponse properly, and addressing the 403 Forbidden response in a meaningful way. Happy coding!