Creating interceptor-like logic just with handlers

InterceptorExample.java

public class InterceptorExample extends AbstractVerticle {
  
  public final static String API_PATH = "/api/v1/";
  public final static String STATIC_FILES = "/static/";
  
  // ...
  private Router router;
  
  @Override
  public void start(Future<Void> future) {
    router = Router.router(vertx);
    attachRoutes();
    vertx
      .createHttpServer()
      .requestHandler(router::accept)
      .listen(future.map<Void>(s -> null).completer());
  }
  
  
  private void attachRoutes() {
    router.get(STATIC_FILES + "*").handler(SomeUtilityClass::createCacheHeaders);
    router.get(STATIC_FILES + "*").handler(StaticHandler.create());
    jsonRoute(API_PATH + "orders", ctx -> {
      final Collection<Order> orders = yourBusinessService.getOrders();
      ctx.put("data", orders);
      ctx.next();
    });
  }
  
  private void jsonRoute(String path, Handler<RoutingContext> businessLogic) {
    router.route(path).handler(JsonUtils::prepareHeaders);
    router.route(path).handler(businessLogic);
    router.route(path).handler(JsonUtils::marshallResult);
  }
}

interface JsonUtils { // this is what you're calling an interceptor
  
  static void prepareHeaders(RoutingContext ctx) {
    if (!ctx.request.headers().contains("something")) {
      ctx.fail(400);
      return;
    }
    ctx.response().putHeader(CONTENT_TYPE, "application/json");
    ctx.next();
  }
  
  static void marshallResult(RoutingContext ctx) {
    ctx.response().end(ctx.get("data").toJsonObject()); // or Jackson if you want to stay generic, or whatever you need
  }
  
  
}