Spring custom annotation validate http header with reflection

I have an endpoint secured with token given in the header. I would like to create my custom annotation so when I annotate the controller method the validation token goes first and then if the token was accurate do the rest of the method. I tried do it with interceptor and it worked but I want to do it using reflection to have custom annotation. I can share some of my code snippet but there is not a lot of code because I couldn't find some that tells me how to get token from header and validate it. And I'm a noob in reflection.

Custom Annotation

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface TokenValidation {
  String token() default "";
}

Controller Class

 @TokenValidation
 @PostMapping("/endpoint")
 public ResponseEntity createComplianceDirectory(@RequestBody ComplianceDirRequest request) {
    return ResponseEntity.status(HttpStatus.OK).build();
 }

Reflection class

    @Value("${token}")
private String token;

private Reflections reflections;

public Reflection() {
    reflections = new Reflections(new ConfigurationBuilder().setUrls(ClasspathHelper.forPackage("com.sampleapp.controller"))
            .setScanners(new FieldAnnotationsScanner()));
    setReflections();
}

public void setReflections() {
    Set<Method> methods = reflections.getMethodsAnnotatedWith(TokenValidation.class);
    RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
    if (requestAttributes instanceof ServletRequestAttributes) {
        HttpServletRequest request = ((ServletRequestAttributes)requestAttributes).getRequest();
        String requestToken = request.getHeader("Authorization");
    }
}

Could someone tell me:

1. How to register that reflection class in spring boot to be invoked when the controller method is called.
2. Is it a good way in my reflection class to retrieve the header ?