@AuthenticationPrincipal

Reference: Spring Docs - AuthenticationPrincipal

• An annotation that injects a user object implementing the UserDetails interface to retrieve the currently logged-in user

  • What is UserDetails?

    • An interface that holds user information (username, password, etc.)

      • Implement this interface to create a class used for login

    • Stored by being encapsulated in Authentication

      • In other words, UserDetails implementation information is taken by the Authentication object stored in the Spring Security Context, and user information is contained in the Authentication object

    → Using @AuthenticationPrincipal, you can extract user information from the Authentication object and have it injected

• Not only UserDetails but other classes containing user information can also be injected, because it extracts user information from Spring Security's Principal object

  • If the class containing user information implements Principal, that class can be used for injection

  • Uses Authentication.getPrincipal() as the method argument!

    • What is java.lang.Object getPrincipal()?

      • Retrieves the user information of the principal being authenticated

        Returns:
        the Principal being authenticated or the authenticated principal after authentication.