LoginController.java

@RestController
public class LoginController {

    @Autowired
    private AuthenticationManager authenticationManager;

    @PostMapping("/token")
    public ResponseEntity<?> authenticate(@RequestBody LoginDto loginDto) {
        // Perform the authentication
        UsernamePasswordAuthenticationToken authenticationToken = new UsernamePasswordAuthenticationToken(
                loginDto.getUsername(),
                loginDto.getPassword()
        );
        Authentication authentication = this.authenticationManager.authenticate(authenticationToken);
        SecurityContextHolder.getContext().setAuthentication(authentication);
        return ResponseEntity.ok(TokenDto.builder().token("winteriscoming").build());
    }

}