Gated Content for assets

I have a client requirement for creating some gated content. So basically, the page ( which contains some assets) should only be reachable after the user has submitted a form. And the assets should also be not accessible directly without submitting the form. So i have created a servlet filter to achieve this, the page logic works fine but when i access a assets directly the request is not reaching the servlet filters. The below is my code please let me know if there is some mistake or there is any other prefered method, i have also tried setting this ServiceRanking(1)

@Component(service = Filter.class,
        property = {
                EngineConstants.SLING_FILTER_SCOPE + "=" + EngineConstants.FILTER_SCOPE_REQUEST,
        })
@@ServiceRankin(-700)
public class GatedContentFilter implements Filter {

    private final Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public void doFilter(final ServletRequest request, final ServletResponse response,
                         final FilterChain filterChain) throws IOException, ServletException {


        final SlingHttpServletRequest slingRequest = (SlingHttpServletRequest) request;

        final SlingHttpServletResponse slingResponse = (SlingHttpServletResponse) response;
        final Resource resource = slingRequest.getResource();

        if(resource.getPath().startsWith("/content/abc")) {
           //page logic
        }
        else if (resource.getPath().startsWith("/content/dam/abc/gated-assets")) {
            //assets logic
        }

        filterChain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig filterConfig) {
    }

    @Override
    public void destroy() {
    }

}