Vert.x 3 says “hello” to NPM users

In pro­gram­ming lit­er­a­ture it has be­come the stan­dard to cre­ate a hello world pro­gram as the first ex­am­ple. In this ar­ti­cle, I’ll be demon­strat­ing how NPM users can quickly get started with vert.x. You will see that it is not that dif­fer­ent and in fact it can be done using the tools you’re used to. Note that al­though we are using NPM we are not re­ly­ing on node.js, all javascript code runs on the JVM.

Hello World Examples

Here are four sim­ple hello world ex­am­ples. The com­ments in the code ex­plain how the code works and the text around it ex­plain what it does and how to test it.

Hello Console

This ex­am­ple is about as plain as it can get. It prints the words ”Hello World” to the ter­mi­nal. If you’re a javascript de­vel­oper you should be al­ready used to npm and know that you al­ways start a project with the file package.json:

{
  "name": "vertx3-hello-console",
  "private": true,
  "dependencies": {
    "vertx3-min": "3.0.0-1"
  },
  "scripts": {
    "start": "./node_modules/.bin/vertx run server.js"
  }
}

Note that we have a de­pen­dency wich is ob­vi­ous vert.x now note that there are 3 flavours of this de­pen­dency:

• min
• base
• full

Ac­cord­ing to your needs you can pick a dif­fer­ent flavour, since for a sim­ple hello world we only need the min­i­mal that is the one we add to the de­pen­dency prop­erty.

Now we need to do a sim­ple hello app, we will call this file ”server.js“:

// Call the console.log function.
console.log("Hello World");

You can run this by ex­e­cut­ing:

npm install
npm start

The first com­mand re­trieve the vert.x stack while the sec­onds starts your pro­gram.

Hello HTTP

I’d guess that while it’s not the only use case for vert.x, most peo­ple are using it as a web ap­pli­ca­tion plat­form. So the next ex­am­ple will be a sim­ple HTTP server that re­sponds to every re­quest with the plain text mes­sage ”Hello World” server.js:

vertx.createHttpServer()
  .requestHandler(function (req) {
    req.response()
      .putHeader("content-type", "text/plain")
      .end("Hello World!");
}).listen(8080);

Now you can reuse the same package.json we’ve just de­fined in the pre­vi­ous sec­tion and start the server with npm start. Once the server starts you can open a browser to http://localhost:8080 and enjoy the mes­sage.

Hello TCP

Vert.x also makes an ex­cel­lent TCP server, and here is an ex­am­ple that re­sponds to all TCP con­nec­tions with the mes­sage “Hello World” and then closes the con­nec­tion server.js:

var server = vertx.createNetServer();
server.connectHandler(function (socket) {
  socket.write("Hello World!\n");
  socket.close();
});

server.listen(7000, "localhost");

Again reuse the pre­vi­ous package.json and test it by doing telnet localhost 7000.

Hello Web

Often you won’t be using vert.x built-​in li­braries be­cause they are de­signed to be very low level. This makes vert.x quick, nim­ble, and easy to main­tain, but if you are plan­ning to build a com­plex ap­pli­ca­tion you want some pro­duc­tiv­ity and rely on a sim­ple web frame­work. For this spe­cific case there is vert.x web, a sim­ple, yet pro­duc­tive frame­work, to build fast web ap­pli­ca­tion with rout­ing, tem­plate ren­der­ing, lots of mid­dle­ware etc…usu­ally not enough to get started on a real world ap­pli­ca­tion. This ex­am­ple shows an HTTP server that re­sponds with “Hello World” to all re­quests to ”/” and re­sponds with a 404 error to every­thing else server.js:

var Router = require("vertx-web-js/router");
var server = vertx.createHttpServer();

var router = Router.router(vertx);

router.get("/").handler(function (ctx) {
  // This handler will be called for "/" requests
  var response = ctx.response();
  response.putHeader("content-type", "text/plain");

  // Write to the response and end it
  response.end("Hello World!");
});

server.requestHandler(router.accept).listen(8080);

In order to test this, you will need to in­stall the vertx3-full stack. There are two ways to do this. You can ei­ther in­stall it glob­ally npm install -g vertx3-full or add it as a de­pen­dency to our package.json as we have done be­fore, for ex­am­ple package.json:

{
  "name": "vertx3-hello-web",
  "private": true,
  "dependencies": {
    "vertx3-full": "3.0.0-1"
  },
  "scripts": {
    "start": "./node_modules/.bin/vertx run server.js"
  }
}

That’s it for now. Hope­fully this will help you get started work­ing with vert.x!