UsernamePasswordAuthenticationToken in Spring Security is a class representing an Authentication object specifically designed for username and password-based authentication. It is a fundamental component in the Spring Security authentication flow.
Here's a breakdown of its key aspects:
• Implementation of Authentication: UsernamePasswordAuthenticationToken implements the org.springframework.security.core.Authentication interface. This interface is the core representation of an authenticated principal within Spring Security once the authentication process is complete.
• Purpose: Its primary purpose is to encapsulate the username and password provided by a user during a login attempt. It can exist in two states:
• Unauthenticated: Initially, it holds the raw username and password provided by the user, before they have been verified. This is often created by filters like UsernamePasswordAuthenticationFilter which extract these credentials from the incoming request.
• Authenticated: After successful authentication by an AuthenticationProvider, the UsernamePasswordAuthenticationToken is updated to include the authenticated principal (e.g., a UserDetails object) and the user's granted authorities (roles).
• Role in Authentication Flow:
• A user submits their username and password (e.g., via a login form).
• A filter (like UsernamePasswordAuthenticationFilter) extracts these credentials and creates an unauthenticated UsernamePasswordAuthenticationToken.
• This token is then passed to the AuthenticationManager for authentication.
• The AuthenticationManager delegates the authentication to a suitable AuthenticationProvider.
• If the credentials are valid, the AuthenticationProvider returns a fully authenticated UsernamePasswordAuthenticationToken which includes the user's details and authorities.
• This authenticated token is then stored in the SecurityContextHolder, making the user's security context available throughout the application.
In essence, UsernamePasswordAuthenticationToken acts as a container for user credentials during the authentication process and, once authenticated, represents the authenticated user and their permissions within the Spring Security framework.
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