Troubleshooting @ Scheduled Tasks in Spring to Update JSON Values

Learn how to fix issues with updating JSON values in a Spring application using the `@ Scheduled` annotation. Get your H2 database reflecting changes as expected.
---
This video is based on the question https://stackoverflow.com/q/71540640/ asked by the user 'Bruno Machado' ( https://stackoverflow.com/u/15240169/ ) and on the answer https://stackoverflow.com/a/71540722/ provided by the user 'Med Elgarnaoui' ( https://stackoverflow.com/u/5296683/ ) 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: @ Scheduled not updating my JSON values to FALSE

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

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Troubleshooting @ Scheduled Tasks in Spring to Update JSON Values

In Java's Spring framework, the @ Scheduled annotation is a powerful tool that allows you to schedule tasks to run at fixed intervals or specific times. However, it can sometimes be tricky, especially when the intended updates aren’t reflected in the database.

The Problem: Scheduled Task Not Updating Values

Consider a scenario where you are trying to reset a specific field (the VOTED attribute) of users in your database to FALSE every day at 1:00 PM. Even though the scheduled task runs (and you see the log message confirming this), the values in the database continue to remain TRUE.

What’s Going Wrong?

This situation often arises due to a misunderstanding of object states and how persistence works in the context of Spring Data JPA (Java Persistence API). Though you're changing the voted flag in your User objects, these changes may not be persisted back to the database unless explicitly instructed to do so.

Let's break down the solution to help you effectively update your VOTED values.

The Solution: Persisting Changes in Your Scheduled Method

To make sure that the changes you are applying to your User objects are saved back to the database, you need to call the save method of your repository after making changes to the entities. Here’s how to do it:

Updated Scheduled Method

Here’s what your updated resetVotes method should look like:

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

Explanation of Changes

Batch Saving: Instead of saving users one by one, use repository.saveAll(userArray). This method accepts a collection and saves all the entities in a single transaction, which is efficient and cleaner.

No Need for Intermediate Steps: Ensuring that you cast your user changes into a list and saving all at once simplifies the code and enhances performance.

Why This Matters

Transactional Control: By using @ Transactional in Spring, you ensure that your operations are atomic. If an error occurs during saving, no changes will be committed, preserving your data integrity.

Validation of Changes: Directly saving after modification permits validation checks specified by entity annotations to occur, ensuring that only valid, intended updates are pushed to your database.

Conclusion

Using the @ Scheduled annotation to update values in your database requires clear commands for persisting those changes. As seen above, the key to ensuring that your scheduled task behaves as expected is not just to modify your objects in memory but also to effectively save those modifications back into the database.

With these changes, you should now be able to see the VOTED values being updated to FALSE at 1:00 PM each day successfully.

If you encounter any further challenges with your Spring applications, remember to review how you're managing your entity states and persistence actions. Happy coding!

Видео Troubleshooting @ Scheduled Tasks in Spring to Update JSON Values канала vlogize