Getting the principal in an AOP interceptor using webflux

Question

I implemented a webflux web API with working oauth authentication (I'm getting the @AuthenticatedPrincipal in controllers). My problem is that I want to implement an AOP interceptor for mybatis Executor, because I need to perform operations based on the Principal identity when an update is performed on DB. I tried to access the Principal through the ReactiveSecurityContextHolder, but the returned SecurityContext is always null...

@Intercepts(@Signature(type = Executor.class, method = "update", args={MappedStatement.class, Object.class}))
public class BaseEntityInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        MappedStatement mappedStatement = (MappedStatement)invocation.getArgs()[0];
        // get sql
        SqlCommandType sqlCommandType = mappedStatement.getSqlCommandType();
        // get parameter , this is the target object that you want to handle
        Object parameter = invocation.getArgs()[1];
        // make sure super class is BaseEntity
        if (parameter instanceof BaseEntityModel) {
            //init
            BaseEntityModel baseEntity = (BaseEntityModel) parameter;

            SecurityContext context= ReactiveSecurityContextHolder.getContext().block();
            Authentication authentication= context.getAuthentication();
            Principal principal = (Principal)authentication.getPrincipal();

            if (SqlCommandType.UPDATE.equals(sqlCommandType)) {
                baseEntity.initUpdate(principal.getUsername());
            }
        }

        return invocation.proceed();
    }

    ...
    
}

What is the correct way to access the Principal? I understand that normally the SecurityContext is saved in ThreadLocal, and probably I must "share" it with my interceptor... how?