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Learn how to dynamically set validation groups in your Spring Boot application using MethodValidationInterceptor and a custom MethodValidationPostProcessor.
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Dynamically Setting Validation Groups in Spring Boot: A Complete Guide

In developing a Spring Boot application, you often find the need to validate request body objects before processing them. While the @ Valid annotation effectively handles such validations, there are scenarios where you may want to set validation groups dynamically based on session-specific information. This flexibility can greatly enhance the capabilities of your validation logic, ensuring that it is relevant to the current session state without cluttering your controller's responsibilities.

Understanding the Challenge

Let's consider a common scenario:

You have an endpoint that updates some data based on a request body.

You'd like to validate the request body dynamically based on user session data.

You want to avoid manual validation checks in your controller, keeping it clean and focused on handling requests.

You initially proceeded with the use of MethodValidationInterceptor, but faced two critical issues:

The @ Valid annotation alone works, but the MethodValidationInterceptor only gets called when you also use the @ Validated annotation on your controller class.

Even when using both annotations, your custom interceptor was not invoked, necessitating an alternative approach to achieve dynamic validation grouping.

Solution Overview

Fortunately, there is a solution that involves creating a custom MethodValidationPostProcessor. This class will allow you to register your session-aware interceptor correctly. Below are the steps to successfully implement dynamic validation groups in your Spring Boot application.

Step 1: Creating the Custom MethodValidationInterceptor

Firstly, you'll need to define your SessionAwareValidationInterceptor that extends the original MethodValidationInterceptor. This interceptor will determine the validation groups based on the current session's attributes.

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Step 2: Implementing the Custom MethodValidationPostProcessor

Next, you'll want to implement a custom MethodValidationPostProcessor. This class will create and provide an instance of your newly created interceptor.

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Step 3: Registering Your Custom PostProcessor as a Bean

To ensure that Spring recognizes your custom post-processor, you need to register it as a bean in your configuration class.

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Step 4: Using Annotations Correctly

To make the entire setup function smoothly, remember to use both of the following annotations appropriately:

@ Validated on the class level (controller class)

@ Valid on the method parameter

This combination ensures that your interceptor is invoked correctly and handles validation groups as intended.

Conclusion

By following the outlined steps, you can dynamically set validation groups based on the user session in your Spring Boot application. This approach provides a clean separation of concerns, allowing your controllers to remain lean while maintaining robust validation logic tailored to specific contexts. Implementing a custom MethodValidationPostProcessor alongside a session-aware interceptor will equip you with the necessary tools to enhance the dynamic validation of request bodies efficiently.

Now, you can confidently build sophisticated validation mechanisms into your Spring Boot applications while keeping your controller logic pure and straightforward.