Skip to main content

My first day playing around with Vert.x

I have been reading quite a lot about Vert.x recently and finally the day before yesterday I sat down and spent some time exploring it by writing some code. Today I would like to present the outcome.

A little bit of history

Like all Reactive frameworks/tool-kits/libraries, Vert.x is inspired by Node.js.
Back when it was released, Node.js shocked many Java developers who looked down on Javascript, on top of owning the Web client side, JS wanted to conquer also the server side!
And thanks to its non-blocking nature, Node.js performed better than typical Java application servers such as Tomcat or Glassfish.
Then the Java world reacted (pun intended) and today Vert.x is one of the most matured reactive technologies for the JVM.

First Vert.x application 

When trying to build my first super-simple reactive (not really) application using Vert.x, I started following this tutorial from the lead developers of Vert.x.
That's great stuff, but I found it a little overwhelming as the first hands-on experience. I understand that the authors are eager to highlight most of the nice features of the technology but I decided to write my own example focusing just in the very basics.

The example application uses Java 8 and Maven and no custom Vert.x configuration (just the default). The main class creates one main verticle and then that verticle creates two more verticles: 
PublisherVerticle and ConsumerVerticle
The PublisherVerticle simply publishes (broadcasts) five messages using JSON as serialization and the ConsumerVerticle receives the messages and just logs their contents.
The messages are just POJOs.

At this point, you may wonder what a verticle is. Vert.x uses its own terminology, I recommend this post in order to get familiar with it. In simple words, a verticle is a Java class whose life-cycle is managed by a Vert.x instance and it can deploy and start other verticles,  it can also communicate with other verticles using the Event Bus.

This example is useful for people who are new to vert.x since it showcases the following:
- how to start vert.x
- how to deploy and start verticles
- how to serialize/marshal a POJO to be encapsulated inside a vert.x message using JSON
- how to publish a message to the vert.x event bus
- how to receive a message from the vert.x event bus
- how to construct a POJO from the received message
- how to stop vert.x
- the asynchronous behaviour of vert.x

And here you have the code.
Looking at the pom.xml you'll see that just adding the vertx-core dependency is enough, as usually, Maven will download the required transient dependencies for us:

As you can see, Vert.x uses Netty for the network communication (I like that it does not force you to use HTTP only) and Jackson for JSON serialization.

To run the example application you just need to execute its main class class, and looking at the output helps to understand the "everything asynchronous by default" philosophy of Vert.x. 
Even the call to start Vert.x is asynchronous, that is why the main method is the first one to finish:

We can also confirm that Vert.x manages the pool of threads for us so we do not need to worry about it.

Since this is a simplistic example, all verticles run on the same JVM/process, but one of the features of Vert.x is its convenience to implement microservices, thus, I could easily refactor the application in order to place each verticle in a different (Maven) module (and run it on its own runtime environment or in different machines) but that's subject for a future post.

Vert.x is a broad topic and I would like to highlight what this post does not cover and I may explore in the future:
- using a different serialization other than JSON (Google protobuffers for example)
- communication with external services (using HTTP or simply TCP or Websockets) either directly or through the Event Bus.
- using Vert.x as the back-end for a Web app (front end could be Angular or React)
- using Vert.x as the back-end for a native mobile app (probably Android since I already have some experience)
- Vert.x cache capabilities (Shared Map) 
- using different instances of Vert.x in the same application

Thanks for reading!


Popular posts from this blog

Kafka + WebSockets + Angular: event-driven microservices all the way to the frontend

In the the initial post of the  Event-driven microservices with Kafka series (see here  or  here ), I talked about the advantages of using event-driven communication and Kafka to implement stateful microservices instead of the standard stateless RESTful ones. I also presented the architecture and the source code of a related proof of concept application. In this post, I would like to show how to extend the asynchronous event-driven communication all the way from Kafka to the Web frontend passing through the Java backend. Hence, in the first post of this series, we got rid of HTTP as the communication protocol among microservices in the backend, and now we are also replacing it (with WebSockets) as the communication protocol between the frontend and the backend. Ok, but why would you do that? Because it provides a better experience to the end user!. Using WebSockets you can build legit  real-time user interfaces, the updates are pushed immediately from the server to the client

A Java dev journey to full-stack: first chapter

The Motivation I am an experienced Java developer and (surprise!) I like Java. I know it is not perfect but it works just fine for me (I enjoy type-safety and I do not consider verbosity a disadvantage, quite the opposite). I also know that some people dislike Java, which is also fine. But recently I decided to step out of my confort zone as developer, my goal isn't to be one of the "cool kids" neither trying to monetize a new skill in the job market. I have a quite practical motivation: I want to be able to build more (different) stuff. That's exactly the same reason why I learnt Android development by myself a couple of years ago. Web applications are ubiquitous, even more than native mobile apps, and thanks to cloud computing, one can easily and inexpensively release their idea/app to the World Wide Web. I already did some Web development in the past, in the bad old days of JSP and JSF, but the process was slow and painful. Nowadays the Web landscape h

Using Apache Kafka to implement event-driven microservices

When talking about microservices architecture, most people think of a network of stateless services which communicate through HTTP (one may call it RESTful or not, depending on how much of a nitpicker one is). But there is another way, which may be more suitable depending on the use case at hand. I am talking about event-driven microservices, where in addition to the classic request-response pattern, services publish messages which represent events (facts) and subscribe to topics (or queues depending on the terminology used) to receive events/messages. To fully understand and embrace this new software design paradigm is not straight-forward but it is totally worth it (at least looking into it). There are several interconnected concepts which need to be explored in order to discover the advantages of event-driven design and the evolutionary path which led to it, for example: Log (including log-structured storage engine and write-ahead log) Materialized View Event Sourcing C o