The org.springframework.security.web.authentication.AuthenticationFilter is a modern filter introduced in Spring Security (starting with version 5.7+) to provide a flexible and unified way of handling authentication.

It is part of the framework's new filter-based architecture that simplifies and replaces older approaches, such as UsernamePasswordAuthenticationFilter, by focusing on declarative configuration for authentication.

The AuthenticationFilter is a modern, flexible filter introduced in Spring Security 5.7+ to unify and simplify authentication handling.

What is AuthenticationFilter?

• A general-purpose filter for handling authentication (e.g., JWT, OAuth2, Basic Auth).
• Dynamically resolves the authentication mechanism using an AuthenticationManagerResolver.

Core Components

1. AuthenticationFilter:
   • The filter that intercepts HTTP requests to extract credentials (e.g., JWT, API key).
   • Delegates authentication to an AuthenticationManager.
2. AuthenticationManagerResolver:
   • Determines which AuthenticationManager to use based on the incoming request.
   • Allows dynamic resolution of authentication strategies.
3. AuthenticationManager:
   • Validates the credentials and produces an Authentication object (or throws an exception if invalid).
4. AuthenticationProvider:
   • The component that does the actual authentication logic (e.g., JWT decoding, validating API keys).

How It Works

1. The AuthenticationFilter intercepts an HTTP request.
2. It uses the AuthenticationManagerResolver to determine the correct AuthenticationManager.