我试图使我的域下不存在的网页去404页。我需要区分404页和其他页。但是，我不知道怎么做。下面的东西不起作用。

@Component(service = Filter.class,
        property = {
            "service.ranking=" + Integer.MIN_VALUE})
    @SlingServletFilter(scope = {SlingServletFilterScope.REQUEST},
        pattern = "/content/foo/.*",
        resourceTypes = "cq:Page",
        extensions = {"html"},
        methods = {"GET"})
    public class NotFoundFilter implements Filter {

        private static final String DEFAULT_METHOD = "GET";

        @Reference
        private UrlOperationsManager urlOperationsManager;

        @Reference
        private RequestResponseFactory requestResponseFactory;

        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
        }

        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
            if (!(request instanceof SlingHttpServletRequest) ||
                !(response instanceof SlingHttpServletResponse)) {
                chain.doFilter(request, response);
                return;
            }

            SlingHttpServletResponse slingResponse = (SlingHttpServletResponse) response;
            //this condition here is not working since slingResponse has no getStatusCode method.
            if(slingResponse.getStatusCode() == 404) {
              //do something
            }
            chain.doFilter(request, response);

    }

    @Override
    public void destroy() {
    }

}