Solving the Spring Boot Validation Issue on POST with DTOs

This guide helps you troubleshoot and solve the issue of validation not working on POST requests in Spring Boot using DTOs. Learn how to fix it efficiently!
---

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: Spring Boot - Validation not working on POST with DTO

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Introduction: Why Validation Matters in Spring Boot

When developing applications using Spring Boot, ensuring that the data sent from the client is valid is crucial. This is where validation comes into play. However, you might encounter a frustrating situation where validation fails silently—resulting in data being accepted and saved to your database, even when it should not be allowed.

In this post, we will address a common issue: validation not working on a POST request with Data Transfer Objects (DTOs) in Spring Boot, and we will walk through how to effectively solve it.

Understanding the Problem

Consider a scenario where you have a controller set up to handle user registrations. You want to ensure that the incoming user data is valid according to specific constraints, such as name, email, and other fields defined in your UserForm DTO. However, you notice that even invalid data is being persisted in your database without any errors or validation feedback.

Here's a snippet of the controller code responsible for handling user creation:

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

Despite using the -Valid annotation on the UserForm DTO, the validation does not trigger as expected. Why is this happening?

Possible Causes

Dependency Conflicts: One of the most common reasons for validation to fail is conflicting dependencies. In many cases, this occurs when a library that may be included by another dependency causes issues with validation execution.

Missing Annotations: While you appear to be using the appropriate annotations on the fields of your DTO, it’s essential to ensure that you have imported the necessary validation libraries correctly.

Stack Trace Misleading: Sometimes, the stack trace may not reveal the root cause of the problem, especially if there are issues with how the beans are configured in the application context.

The Solution: Removing Conflicting Dependencies

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

Why This Worked

Conflict Resolution: The hibernate-validator dependency was causing conflicts with the validation framework being used. By removing it, the validation system could function properly without interference.

No Errors in Stack Trace: Interestingly enough, even without the proper validator, the absence of errors in your stack trace can be deceiving, leading you to believe everything was functioning correctly.

Conclusion

Validation in Spring Boot is an essential component for maintaining data integrity, especially when working with POST requests and DTOs. If you encounter a situation where validation fails silently, always consider checking for library conflicts and verifying your dependencies.

By following the steps outlined in this post, you can effectively troubleshoot and solve validation issues within your Spring Boot application. Ensuring that your setup is clean and free from conflicting dependencies will help keep your data safe and valid.

Call to Action

If you've faced similar issues in Spring Boot, share your experiences in the comments below! Let’s help each other navigate the quirks of Spring Boot development together.