How does Spring Security associate an incoming request with a specific client and its access rights?

Spring Security links an incoming HTTP request to a specific client and its access rights through authentication and authorization mechanisms.

1. Authentication: When a user makes the first request, they enter their credentials (login and password). Spring Security verifies these through the AuthenticationManager, and if the data is correct, it creates an Authentication object that stores information about the user and their roles.

2. Session or token: After successful authentication, Spring Security associates the user with a session (for example, via a JSESSIONID cookie) or issues a token (such as JWT). This identifier is sent to the server in subsequent requests.

3. SecurityContext: Spring Security stores the Authentication object in the SecurityContext, which is linked to the current execution thread (usually via ThreadLocal). With each request, Spring Security filters extract user data from the session or token and restore the SecurityContext.

4. Authorization: Based on information from the SecurityContext (for example, user roles), Spring Security checks whether the user has access to the requested resource.

Thus, the connection between the request and the client and its rights is ensured through authentication, state storage (session or token), and the use of SecurityContext for access rights verification.