vertx-starter

Overview

This is a simple application to get you started with the Vert.x toolkit. It is a companion to the tutorial Reactica: reactive programming and Vert.x.

The code features two processes running simultaneously. One process (vertx.setPeriodic()) writes a message to the console every two seconds, while the other (vertx.createHttpServer()) serves requests on HTTP port 8080.

The code

Here's the heart of the source code:

    @Override
    public void start() {
        vertx.setPeriodic(2000, counter -> {
            long runTime = (System.currentTimeMillis() - startTime) / 1000;
            System.out.println("Server run time: " + runTime + " seconds.");
        });

        vertx.createHttpServer()
            .requestHandler(req -> {
                System.out.println("Request #" + counter++ +
                                   " from " + req.remoteAddress().host());
                req.response().end("Hello from Coderland!");
            })
            .listen(8080);
        
        System.out.println("----------------------------------------------");
        System.out.println("---> Coderland now listening on localhost:8080");
        System.out.println("----------------------------------------------");
    }

    @Override
    public void stop() {
        System.out.println("---------------------------------------------");
        System.out.println("---> Coderland signing off! Have a great day.");
        System.out.println("---------------------------------------------");
    }

Building and running the code

The following commands build and run the code:

mvn clean package
java -jar target/vertx-starter-1.0-SNAPSHOT.jar

Sample output

Sample output looks like this:

doug@dtidwell-mac:~/vertx-starter $ java -jar target/vertx-starter-1.0-SNAPSHOT.jar 
----------------------------------------------
---> Coderland now listening on localhost:8080
----------------------------------------------
Jun 26, 2019 8:33:59 AM io.vertx.core.impl.launcher.commands.VertxIsolatedDeployer
INFO: Succeeded in deploying verticle
Server run time: 2 seconds.
Server run time: 4 seconds.
Request #1 from 192.168.1.67
Server run time: 6 seconds.
Request #2 from 192.168.1.76
Server run time: 8 seconds.
Server run time: 10 seconds.
Request #3 from 0:0:0:0:0:0:0:1
Request #4 from 0:0:0:0:0:0:0:1
Server run time: 12 seconds.
Server run time: 14 seconds.
Server run time: 16 seconds.
Request #5 from 192.168.1.67
Server run time: 18 seconds.
Server run time: 20 seconds.
Request #6 from 192.168.1.76
Server run time: 22 seconds.
Server run time: 24 seconds.
^C---------------------------------------------
---> Coderland signing off! Have a great day.
---------------------------------------------

Some notes on the output:

First of all, notice that we @Override the start() and stop() methods. Overriding the start() method is typical because you probably want to set up some things when your verticle is loaded. Overriding stop() is less common, but notice that typing Ctrl+C at the command line invoked the stop() method before the system killed the code.

Second, the print statements in the start() method were executed before the verticle was up and running. The Vert.x runtime doesn’t print the “Succeeded in deploying verticle” message until the start() method is finished. The output says the code is listening on port 8080, but that’s not technically true until a fraction of a second later when the verticle is fully loaded.

You can see the two asynchronous processes the verticle uses. One (vertx.setPeriodic()) is invoked every two seconds, the other (vertx.createHttpServer()) is invoked whenever an HTTP request comes in on localhost:8080. As long as the verticle is running, these two processes operate independently of each other.

The Reactica roller coaster

Coderland's tutorial Reactica: reactive programming and Vert.x features a complete, sophisticated example of a system of reactive Vert.x microservices that work together.

🎁 REPO: The Reactica roller coaster source code

📄 Reactica roller coaster overview

🎬 VIDEO: An overview of the Reactica roller coaster

📖 Clement Escoffier's excellent book Building Reactive Microservices in Java, available for free from the Red Hat Developer Program

📄 Andre Staltz's The introduction to Reactive Programming you've been missing

📄 The Reactive Manifesto

📄 The Vert.x home page

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