Spring: check if annotation is used but bean is not present

Question

I have some homemade annotation (let us call it @A) that can be used on RequestMappings to work with some OncePerRequestFilter (called MyFilter here).

I have made an autoconfiguration to conditionally create the MyFilter bean, and I now wish to perform the following check: if @A is used on at least one of my request mappings, throw an error if no instance of MyFilter is available.

In trying so, I have tried:

• using Jakarta validation with a method inside the autoconfiguration, with and without @Validated/@Valid on the method and/or the autoconfiguration:

  @AssertTrue(message = "Annotation A may not be used, no instance of MyFilter was provided")
  private boolean isFilterAvailableIfAnnotationIsUsed(RequestMappingHandlerMapping requestMappingHandlerMapping, Optional<MyFilter> myFilter) {
    if (myFilter.isEmpty()) {
      for (HandlerMethod handlerMethod : requestMappingHandlerMapping.getHandlerMethods().values()) {
        if (handlerMethod.hasMethodAnnotation(A.class)) {
          return false;
        }
      }
    }
  
    return true;
  }
  

• looking into @PostConstruct, but it does not take beans as arguments
• checking out BeanPostProcessor, but I am not sure I could use it that way

Now, the only idea I have left is to create a dummy bean that depends on RequestMappingHandlerMapping and Optional<MyFilter>, and which goal is just to throw an exception if the conditions are satisfied.

Is there a clean way of performing something like this?