Micronaut Security Basics: A Beginner’s Guide to Securing Your Micronaut Applications

In the era of microservices and cloud-native applications, securing your APIs is no longer optional—it’s essential. Micronaut Security Basics gives you a head start in understanding how to secure your Micronaut-based applications using built-in features like JWT authentication, HTTP Basic Auth, and role-based authorization.

Micronaut provides a robust and extensible security module that integrates seamlessly with modern authentication and authorization standards. In this post, we’ll cover everything from configuration to implementation with real-world examples using the package com.kscodes.micronaut.security.

Micronaut Security Basics

🔐 What is Micronaut Security?

Micronaut Security is a built-in module for handling authentication, authorization, and user management within Micronaut applications. It supports a variety of security mechanisms, including:

  • HTTP Basic Authentication
  • JWT (JSON Web Token)
  • OAuth2/OpenID Connect
  • LDAP
  • Session-based Auth

It’s lightweight, fast, and ideal for microservice architectures.

🔧 Getting Started with Micronaut Security

1. Add Security Dependencies

Update your build.gradle or pom.xml to include Micronaut Security:


dependencies {
    implementation("io.micronaut.security:micronaut-security-jwt")
}

For Maven:



  io.micronaut.security
  micronaut-security-jwt

⚙️ Basic Security Configuration

Create application.yml:


micronaut:
  application:
    name: micronaut-security-demo
  security:
    enabled: true
    token:
      jwt:
        signatures:
          secret:
            generator:
              secret: "mysecretkey"
    authentication: bearer

👤 Creating a Simple Authentication Controller

com.kscodes.micronaut.security.AuthController.java


package com.kscodes.micronaut.security;

import io.micronaut.http.annotation.*;
import io.micronaut.security.authentication.*;
import io.micronaut.security.token.jwt.render.BearerAccessRefreshToken;
import jakarta.inject.Inject;
import reactor.core.publisher.Mono;

@Controller("/auth")
public class AuthController {

    @Inject
    AuthenticationProviderUserPassword authProvider;

    @Post("/login")
    public Mono login(@Body UsernamePasswordCredentials credentials) {
        return Mono.from(authProvider.authenticate(null, credentials))
                   .map(auth -> new BearerAccessRefreshToken("myApp", auth.getName(), auth.getRoles()));
    }
}

👥 Custom Authentication Provider

com.kscodes.micronaut.security.BasicAuthProvider.java


package com.kscodes.micronaut.security;

import io.micronaut.security.authentication.*;
import jakarta.inject.Singleton;
import org.reactivestreams.Publisher;
import reactor.core.publisher.Mono;
import java.util.List;

@Singleton
public class BasicAuthProvider implements AuthenticationProvider {

    @Override
    public Publisher authenticate(AuthenticationRequest request) {
        String identity = request.getIdentity().toString();
        String secret = request.getSecret().toString();

        if (identity.equals("admin") && secret.equals("admin123")) {
            return Mono.just(AuthenticationResponse.success(identity, List.of("ROLE_ADMIN")));
        } else {
            return Mono.just(new AuthenticationFailed());
        }
    }
}

🔒 Securing Endpoints with Role-Based Access

com.kscodes.micronaut.security.AdminController.java


package com.kscodes.micronaut.security;

import io.micronaut.http.annotation.*;
import io.micronaut.security.annotation.Secured;
import io.micronaut.security.rules.SecurityRule;

@Controller("/admin")
public class AdminController {

    @Secured("ROLE_ADMIN")
    @Get("/dashboard")
    public String dashboard() {
        return "Welcome to the Admin Dashboard";
    }
}

🧪 Testing the Flow

  1. Login with /auth/login using:

{
  "username": "admin",
  "password": "admin123"
}

Use JWT token from the response to access /admin/dashboard.

Unauthorized users will get 403 Forbidden.

📌 Best Practices

  • Store secrets securely (e.g., Vault, AWS Secrets Manager).
  • Use HTTPS in production.
  • Implement token expiration and refresh mechanisms.
  • Integrate OAuth2 or external IdPs for scalable authentication.

📚 External References

✅ Conclusion

Micronaut Security Basics provide a clean and efficient way to secure your services. With built-in support for JWT and role-based access, you can protect your endpoints with minimal configuration. The com.kscodes.micronaut.security package shown here is a great starting point to build scalable, secure applications.

Whether you’re building REST APIs or microservices, understanding Micronaut Security will give your applications the foundational layer of protection they need.