Weld Vert.x Next?

2017-8-7   vertx , integration   Martin Kouba

Last year Weld team announced the weld-vertx project (see also Weld meets Vert.x and Update on weld-vertx articles). The goal was clear - bring the CDI programming model into the Vert.x ecosystem. Since then, several things have changed. Two new modules were added, CDI 2 and Weld 3 is now used by default, and two final versions were released. I think it’s a good time to summarize the features and plans for future.

What Is It Good For?

First of all, it offers a mature component model for business logic in your Vert.x applications. A reasonable component model helps making your applications maintainable and scalable in terms of development and reusability. So the primary intention is to implement the business logic as CDI beans and use Vert.x APIs for everything else.

Modules

So far there are four modules available:

  1. The Core module starts/stops the Weld SE container and to notifies CDI observer methods when a message is sent via Vert.x event bus. Also you can inject io.vertx.core.Vertx and io.vertx.core.Context in any CDI bean.

  2. The Web module allows to configure the router (a component responsible to find the "logic" to handle an HTTP request) in a declarative way, using @org.jboss.weld.vertx.web.WebRoute annotation. Of course, you can register routes programatically. But what if there are hundreds of routes? The more complicated the REST API is the more difficult it is to maintain the code.

  3. The Service Proxy module makes it possible to inject and invoke service proxies (as defined in https://github.com/vert-x3/vertx-service-proxy).

  4. The Probe module enables Weld Probe development tool in a Vert.x application.

How Do I Use It In My Vert.x Webapp?

Let’s enhance an existing webapp in four simple steps.

1. Project Configuration

Jus add the following dependency to your pom.xml and beans.xml into src/main/resources/META-INF (this will enable CDI).

<dependency>
  <groupId>org.jboss.weld.vertx</groupId>
  <artifactId>weld-vertx-web</artifactId>
  <version>${version.weld-vertx}</version>
</dependency>
Note
 This also brings in org.jboss.weld.vertx:weld-vertx-core, Vert.x and Weld dependencies.

2. Start CDI Container

Deploy WeldWebVerticle and configure router:

class MyVertxApp {

     public static void main(String[] args) {
         final Vertx vertx = Vertx.vertx();
         // ...deploy other existing verticles
         final WeldWebVerticle weldVerticle = new WeldWebVerticle();
         vertx.deployVerticle(weldVerticle, result -> {
             if (result.succeeded()) {
                 vertx.createHttpServer().requestHandler(weldVerticle.createRouter()::accept).listen(8080);
             }
         });
     }
 }

3. Observe Events

Create a CDI observer method to consume messages from the Vert.x event bus. @VertxConsumer qualifier is used to specify the address the consumer will be registered to. VertxEvent is a wrapper of a Vert.x message.

@ApplicationScoped
class HelloBean {

  void consumerWithDependencies(@Observes @VertxConsumer("hello.address") VertxEvent event, HelloService service) {
    // Reply to the message - io.vertx.core.eventbus.Message.reply(Object)
    event.setReply(service.hello());
  }
}
Note
 Since we’re working with regular observer methods, additional parameters may be declared (next to the event parameter) - these parameters are injection points.

4. Declare Routes

Annotate a class implementing Handler<RoutingContext> with @org.jboss.weld.vertx.web.WebRoute:

@WebRoute("/hello") // Matches all HTTP methods
class HelloHandler implements Handler<RoutingContext> {

    @Inject
    HelloService service;

    @Override
    public void handle(RoutingContext ctx) {
        ctx.response().setStatusCode(200).end(service.hello());
    }
}

This will be translated into something like:

void integrationPseudoCode() {
  HelloHandler hello = produceInjectedInstanceOfHelloHandler();
  Router router = obtainRouterInstance();
  router.route("/hello").handler(hello);
}
Note
 @WebRoute is repeatable, i.e. if multiple annotations are declared on a handler class a single handler instance is used for multiple routes.

5. Enjoy and Celebrate

And that’s it. Fairly straightforward, isn’t it?

Future and Plans

So far there are no new features on the roadmap. The plan is to provide bugfix releases as needed. But weld-vertx is an open source project and so the future is in hands of the community. Feel free to create issues, share ideas, throw feature requests and send pull requests!