is there a way to use the localstorage-function of a browser using vert.x?

router.route().handler(SessionHandler.create(LocalSessionStore.create(vertx)));
        router.get("/set").handler(ctx -> {
            ctx.session().put("key", "value");
            ctx.response().end("Session value set");
        });
        router.get("/get").handler(ctx -> {
            String value = ctx.session().get("key");
            ctx.response().end("Session value: " + value);
        });

seems to use a backend-hashmap – not the browser-build-in function.