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Discover how to audit changes in MongoDB subdocuments using Javers effectively. Learn the necessary steps and code snippets to track all modifications, including nested structures.
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Auditing MongoDB Subdocuments with Javers: How to Ensure Accurate Change Tracking

When working with databases like MongoDB, it’s essential to keep track of changes, especially when dealing with subdocuments. If you've been using Javers for this purpose, you might run into challenges, like changes in subdocuments not appearing in the observed changes. This post discusses a common issue users face and provides clear solutions to effectively audit subdocuments with Javers.

The Problem

A user reported that while trying to audit subdocument changes in MongoDB using Javers, only certain properties were showing up in the change log. Specifically, when making modifications to a workflowState, the only property that reflected a change was lastModifiedDate. The following document illustrates the structure involved:

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

Upon attempting to capture the changes made to the workflowState, they only observed changes to lastModifiedDate. This situation prompted a question: “Am I missing something here?”

Understanding the Root Cause

The underlying issue in this scenario is that Javers wasn't capturing changes to nested objects by default. This is a common limitation when dealing with subdocuments or complex objects in audit scenarios. In such cases, the necessary call to track child value objects must be explicitly made in the query.

Key Insight

To have Javers audit changes in subdocuments, you must use the withChildValueObjects() method when building your query. This method allows Javers to recognize and track changes to the child objects within your primary entity.

The Solution

Here’s how to effectively capture changes to subdocuments using Javers. Follow these steps:

Step 1: Update Your Query

In your existing implementation, update the code that retrieves changes as follows:

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

By including .withChildValueObjects(), you inform Javers to inspect and audit not only the parent document but also any nested documents or child value objects, like workflowState in this example.

Step 2: Check Your Change Capturing Logic

Ensure that your logic capturing changes is implemented correctly. The process already looks correct as you are using findChanges with the instance of your entity. With the new query, every modification to workflowState will be tracked and logged properly.

Step 3: Test Functionality

After making the above changes, test your functionality again. Modify the workflowState as you did previously, and you should expect to see changes reflected for properties like isTerminus, label, and entry in addition to lastModifiedDate.

Conclusion

Auditing subdocument changes in MongoDB with Javers can seem daunting when changes aren't appearing as expected. However, by using .withChildValueObjects() in your query, you can easily capture and track changes to nested structures. With this guide, you should be well-equipped to enhance your auditing capabilities and ensure that all modifications are correctly logged.

Additional Tips

Always refer to Javers documentation for the latest methods and options to enrich your auditing experience.

Consider implementing unit tests for auditing to automatically verify change capturing during development.

With these best practices, you can maintain accurate and comprehensive change logs in your MongoDB applications.