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Discover how to fix the issue of corrupted Excel files when downloading from AWS API Gateway in an Angular application. Learn about required headers and ensure a smooth user experience.
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Solving the Corrupted Excel Files Issue in Angular When Downloading from AWS API Gateway

When developing web applications, file downloads are a common feature, especially for reporting and data analysis tasks. However, developers sometimes encounter frustrating issues—like corrupted Excel files when downloading from an AWS API Gateway in an Angular application. If you've faced this problem, you're not alone.

In this article, we'll explore why this issue occurs and how you can resolve it efficiently.

Understanding the Problem

In your scenario, you're exporting an Excel file from your backend, which operates correctly during local development. But once you deploy that backend to AWS and access it via the AWS API Gateway, the downloaded Excel file ends up being corrupted. Interestingly, the same file can be successfully requested through tools like Postman, highlighting that the problem lies in the interaction between Angular and the API Gateway.

Key Takeaways:

The Excel file works locally and via Postman but gets corrupted when accessed through Angular.

The issue is likely linked to how the application handles the HTTP response from the API.

Dissecting the Solution

The main point of failure is Angular's handling of the Blob type for files downloaded from your API. The Angular HttpClient infers the Blob's format based on the response headers sent by the server. If the headers aren't set correctly, the Blob may be mishandled, resulting in a corrupted file.

Solution Steps

Set Appropriate Request Headers:
To fix the issue, you need to explicitly inform Angular about the expected response type using the appropriate headers.

Updated Angular Export Method:
Change your export function in Angular to include the Accept header in your request:

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

Testing the Solution:
After making the above changes, test the download functionality again. The file should download successfully without corruption.

Key Takeaway:

By specifying the Accept header, you're providing crucial information that ensures Angular's HTTP service understands the content type of the requested resource. This change results in Angular correctly processing the Blob response.

Conclusion

Resolving the issue of corrupted Excel files when downloading from an AWS API Gateway in an Angular application boils down to ensuring that the correct request headers are set. By informing Angular of the expected Blob type, you can successfully download files without corruption.

Feel free to apply these changes to your code and enjoy seamless file downloads in your Angular application. If you continue to face issues, remember to check your backend setup and ensure that all response headers are correctly configured.

Now you can provide your users with a smooth experience when exporting and downloading reports!