Скачать или смотреть Handling null Values in Reactive Programming with Mono.zip in Spring WebFlux

Learn how to manage `null` values in Mono.zip operations using Spring WebFlux. Discover a utility method to transform optional Monos in your reactive programming workflow.
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This video is based on the question https://stackoverflow.com/q/62517565/ asked by the user 'Matley' ( https://stackoverflow.com/u/6022333/ ) and on the answer https://stackoverflow.com/a/62529566/ provided by the user 'Michael Berry' ( https://stackoverflow.com/u/551406/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling null Values in Reactive Programming with Mono.zip in Spring WebFlux

Reactive programming can sometimes be tricky, especially when dealing with null values or empty responses from database queries. One common scenario developers encounter is using Mono.zip in Spring WebFlux, where one of the Monos might return Mono.empty. This can lead to potential issues if not handled correctly. In this post, we'll explore a way to handle cases where one of your data sources might return an empty Mono, allowing your application to function smoothly.

The Problem

Consider the following scenario in your code:

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Here you are attempting to fetch credentials using two IDs - aCredentialsId (required) and bCredentialsId (optional). However, it's possible for the second call to return an empty Mono when bCredentialsId is null. This raises the question: How can you safely deal with the potential for an empty Mono when trying to zip two Monos together?

The Solution

A robust solution is to create a utility method that will help transform your Monos. This method will ensure that you always receive an Optional instead of a potentially empty Mono. Here’s how to implement this:

Step 1: Create a Utility Method

First, you can create a utility method in a separate class, like so:

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Step 2: Transform Your Mono

Now, you can leverage this utility method to transform the second Mono in your zip operation. Here’s how it can be incorporated into your existing code:

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Step 3: Handle the Result

With the above setup, if the second Mono returns empty, you will receive Optional.empty() instead. This allows you to handle the case without running into null pointer exceptions or similar runtime issues. You can then check if the Optional has a value later during processing:

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Conclusion

Handling potentially empty Monos gracefully is an essential skill in reactive programming with Spring WebFlux. By utilizing the optional utility method, you can ensure that your application remains robust and clear of null-related issues. This approach enhances your code’s readability and maintainability while working with Mono.zip.

In summary, don't let null values disrupt your flow - instead, embrace the power of optional Monos!