Preauthenticatedauthenticationtoken

preauthenticatedauthenticationtoken:

The PreAuthenticatedAuthenticationToken class is a subclass of AbstractAuthenticationToken in Spring Security. It represents a token that has already been authenticated by an external system or module, such as a Single Sign-On (SSO) provider.

When using PreAuthenticatedAuthenticationToken, the authentication process is bypassed since the token is already considered authenticated. This is useful when integrating with external authentication mechanisms.

Example:

public class CustomAuthenticationProvider extends AbstractPreAuthenticatedAuthenticationProvider {
    @Override
    protected UserDetails retrieveUser(String principal, PreAuthenticatedAuthenticationToken authentication) {
        // Retrieve user details using the provided principal (e.g., username)
        UserDetails userDetails = userService.loadUserByUsername(principal);

        // Additional validation and checks can be performed here

        return userDetails;
    }

    // Other overridden methods if needed
}

In the example above, a custom authentication provider is implemented by extending AbstractPreAuthenticatedAuthenticationProvider. The retrieveUser() method is overridden to retrieve the user details based on the provided principal (e.g., username).

By using PreAuthenticatedAuthenticationToken, you can authenticate the user based on the external token without going through the regular authentication process.