Solving Spring Boot Security Custom Filter Invocation Issues: A Deep Dive into Filter Configurations

Discover why your Spring Boot security custom filter isn't being invoked and learn how to resolve configuration issues for seamless JWT token validation in microservices.
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Understanding the Problem: Custom Filter Not Invoked in Spring Boot Security

If you're developing a Spring Boot application and finding that your custom security filter isn't being invoked, you're not alone. This common issue can be particularly troublesome when dealing with JWT token validation across multiple services in a microservice architecture.

In this guide, we’ll break down how your security filters work, why a simple configuration issue can prevent your custom filters from being triggered, and most importantly, how you can resolve this to ensure your security architecture functions as intended.

The Architecture Overview

You have an AuthService responsible for authenticating users and providing a JWT token, which users then use to access various microservices, like EmployeeService. Each service validates the JWT to ensure it’s valid without requiring each microservice to implement complex authentication logic internally.

Workflow Summary

The user logs in and receives a JWT from AuthService.

The user includes this JWT in the Authorization header when making requests to other services.

EmployeeService is supposed to validate this token through a custom filter (AppSecurityFilter) which calls an endpoint in AuthService to confirm the validity of the JWT.

Why Custom Filters Might Not Invoke

Configuration Issue

Despite your correct intention to add a custom filter in your ApplicationSecurity configuration, the filter might not be invoked due to configuration problems stemming from the use...

@RefreshScope: This annotation is often used to refresh beans when configuration changes (like property changes) happen. However, it can cause unintended behavior in Spring Security, leading to the filter not being part of the correct filter chain.

Symptoms of the Problem

Upon debugging, you might notice that the Spring Security filter chain logs show two different configurations upon application startup. One includes your custom filter, while the other falls back to a default configuration without it.

Solution: Removing @RefreshScope

After extensive investigation, the best course of action is straightforward—simply remove the @RefreshScope annotation from the ApplicationSecurity class. Here’s how your configuration should look without it:

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Verification Steps

Startup Logs: After removing the annotation and restarting your application, check the logs to verify that only one filter chain is registered and it includes your custom filter.

Testing JWT Validation: Make a request to EmployeeService including a JWT token. Ensure your filter is invoked and correctly validates the token by checking if the user details are set in the SecurityContext.

Why Removing @RefreshScope Works

Removing @RefreshScope prevents Spring Security from creating a new instance that might not properly include your custom filter in its processing chain, thereby ensuring that all intended security configurations are applied correctly.

Conclusion

By understanding the underlying issues with Spring Security’s filter chain and the impact of the @RefreshScope annotation, you can avoid common pitfalls in microservice authentication. Always review your security configurations to ensure that they align with your architecture and intended workflow.

If you continue to experience issues, consider reaching out to the developer community or consulting official documentation for further insights.

Feel free to share your experiences and solutions in the comments below!