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Learn how to manage errors and implement retry logic with `WebClient` in Spring Boot without throwing exceptions.
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This video is based on the question https://stackoverflow.com/q/78027862/ asked by the user 'czr_RR' ( https://stackoverflow.com/u/11807683/ ) and on the answer https://stackoverflow.com/a/78028875/ provided by the user 'amir rad' ( https://stackoverflow.com/u/10011738/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing Errors with WebClient in Spring Boot

Using the WebClient for making HTTP requests in a Spring Boot application can sometimes lead to unexpected challenges when you want to implement error handling and retry mechanisms. Particularly, developers often find that the retryWhen operator doesn't execute as expected when it's combined with exchangeToMono. If you're facing a situation where retries are not functioning correctly, this guide will guide you through resolving this issue.

The Problem: Retries Not Working

When you perform an HTTP request using WebClient, you may encounter scenarios where the endpoint responds with non-200 status codes (e.g., 404, 500). In such cases, the code snippet you provided will log an error but won't repeat the request as intended. The primary question then becomes:

How can you effectively manage such errors, allowing retries while failing silently—without throwing an exception?

Are retryWhen and exchangeToMono mutually exclusive?

The Solution: Combining Operators

To implement robust error handling while still allowing for retries, you can combine various reactive operators effectively. Here’s how you can structure your code:

Step-by-Step Breakdown

Here’s an example that combines exchangeToMono, retryWhen, and onErrorResume:

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

Explanation of Key Components

exchangeToMono: This operator maps the response to a Mono type, allowing you to react based on the HTTP response status. If you're dealing with a non-200 status code, it triggers a custom error.

retryWhen: This operator allows you to specify how many times you want to retry the request after a failure. In the above example, it will attempt the request up to 5 times, waiting 5 seconds between each attempt.

onErrorResume: This operator enables you to handle the error gracefully when all retries fail. Instead of throwing an exception, which can break the flow, it allows you to return an empty Mono, effectively failing silently.

Conclusion

By structuring your WebClient request this way, you can successfully manage retries without facing issues related to error handling. The key is ensuring that exceptions are raised at the right time to allow the retryWhen operator to function. This setup allows for a cleaner and more user-friendly error management strategy that doesn't overwhelm the user with exceptions.

Now you are equipped to handle errors and implement retries effectively using WebClient in your Spring Boot applications. Happy coding!