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Getting Started with Quarkus

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Key Takeaways

  • Quarkus is a new technology aimed at cloud development.
  • With Quarkus, you can take advantage of smaller runtimes optimized for the cloud.
  • You don’t need to relearn new APIs. Quarkus is built on top of the best-of-breed technologies from the last decade, like Hibernate, RESTEasy, Vert.x, and MicroProfile.
  • Quarkus is productive from day one.
  • Quarkus is production ready.

Quarkus created quite a buzz in the enterprise Java ecosystem in 2019. Like all other developers, I was curious about this new technology and saw a lot of potential in it. What exactly is Quarkus? How is it different from other technologies established in the market? How can Quarkus help me or my organization? Let’s find out.

What is Quarkus?

The Quarkus project dubbed itself Supersonic Subatomic Java. Is this actually real? What does this mean? To better explain the motivation behind the Quarkus project, we need to look into the current state of software development.

From On-Premises to Cloud

The old way to deploy applications was to use physical hardware.  With the purchase of a physical box, we  paid upfront for the hardware requirements. We had already made the investment, so it wouldn’t matter if we used all the machine resources or just a small amount. In most cases, we wouldn’t care that much as long as we could run the application. However, the Cloud is now changing the way we develop and deploy applications.

In the Cloud,  we pay exactly for what we use. So we have become pickier with our hardware usage. If the application takes 10 seconds to start, we have to pay for these 10 seconds even if the application is not yet ready for others to consume.

Java and the Cloud

Do you remember when the first Java version was released? Allow me to refresh your memory — it was in 1996. There was no Cloud back then. In fact, it only came into existence several years later. Java was definitely not tailored for this new paradigm and had to adjust. But how could we change a paradigm after so many years tied to a physical box where costs didn’t matter as much as they do in the Cloud?

It’s All About the Runtime

The way that many Java libraries and frameworks evolved over the years was to perform a set of enhancements during runtime. This was a convenient way to add capabilities to your code in a safe and declarative way. Do you need dependency injection? Sure! Use annotations. Do you need a transaction? Of course! Use an annotation. In fact, you can code a lot of things by using these annotations that the runtime will pick and handle for you. But there is always a catch. The runtime requires a scan of your classpath and classes for metadata. This is an expensive operation that consumes time and memory.

Quarkus Paradigm Shift

Quarkus addressed this challenge by moving expensive operations like Bytecode Enhancement, Dynamic ClassLoading, Proxying, and more to compile time. The result is an environment that consumes less memory, less CPU, and faster startup. This is perfect for the use case of the Cloud, but also useful for other use cases. Everyone will benefit from less resources consumption overall, no matter the environment.

Maybe Quarkus is Not So New

Have you heard of or used technologies such as CDI, JAX-RS, or JPA? If so, the Quarkus stack is composed of these technologies that have been around for several years. If you know how to develop these technologies, then you will know how to develop a Quarkus application.

Do you recognize the following code?

public class BookApi {
    BookRepository bookRepository;

    Response get(@PathParam("id")Long id) {
        return bookRepository.find(id)

Congratulations, you have your first Quarkus app!

Best of Breed Frameworks and Standards

The Quarkus programming model is built on top of proven standards, be it official standards or de facto standards. Right now, Quarkus has first class support for technologies like Hibernate, CDI, Eclipse MicroProfile, Kafka, Camel, Vert.x, Spring, Flyway, Kubernetes, Vault, just to name a few. When you adopt Quarkus, you will be productive from day one since you don’t really need to learn new technologies. You just use what has been out there for the past 10 years.

Are you looking to use a library that isn’t yet in the Quarkus ecosystem? There is a good chance that it will work out of the box without any additional setup, unless you want to run it in GraalVM Native mode. If you want to go one step further, you could easily implement your own Quarkus extension to provide support for a particular technology and enrich the Quarkus ecosystem.

Quarkus Setup

So, you may be asking if there is something hiding under the covers. In fact yes there is. You are required to use a specific set of dependencies in your project that are provided by Quarkus. Don’t worry, Quarkus supports both Maven and Gradle. For convenience, you can generate a skeleton project in Quarkus starter page, and select which technologies you would like to use. Just import it in your favorite IDE and you are ready to go. Here is a sample Maven project to use JAX-RS with RESTEasy and JPA with Hibernate:

<?xml version="1.0"?>
<project xsi:schemaLocation="" xmlns=""

You might have noticed that most of the dependencies start with the groupId io.quarkus and that they are not the usual dependencies that you might find for Hibernate, Resteasy, or Junit.

Quarkus Dependencies

Now, you may be wondering why Quarkus supplies their own wrapper versions around these popular libraries. The reason is to provide a bridge between the library and Quarkus to resolve the runtime dependencies at compile time. This is where the magic of Quarkus happens and provides projects with fast start times and smaller memory footprints.

Does this mean that you are constrained to use only Quarkus specific libraries? Absolutely not. You can use any library you wish. You run Quarkus applications on the JVM as usual, where you don’t have limitations.

GraalVM and Native Images

Perhaps you already heard about this project called GraalVM by Oracle Labs? In essence, GraalVM is a Universal Virtual Machine to run applications in multiple languages. One of the most interesting features is the ability to build your application in a Native Image and run it even faster! In practice, this means that you just have an executable to run with all the required dependencies of your application resolved at compile time. This does not run on the JVM — it is a plain executable binary file, but includes all necessary components like memory management and thread scheduling from a different virtual machine, called Substrate VM to run your application.

For convenience, the sample Maven project already has the required setup to build your project as native. You do need to have GraalVM in your system with the native-image tool installed. Follow these instructions on how to do so. After that, just build as any other Maven project but with the native profile: mvn verify -Pnative. This will generate a binary runner in the target folder, that you can run as any other binary, with ./project-name-runner. The following is a sample output of the runner in my box:

[io.quarkus] (main) code-with-quarkus 1.0.0-SNAPSHOT (powered by Quarkus 1.3.0.Final) started in 0.023s. Listening on:
INFO  [io.quarkus] (main) Profile prod activated.
[io.quarkus] (main) Installed features: [agroal, cdi, hibernate-orm, narayana-jta, resteasy, resteasy-jsonb]

Did you notice the startup time? Only 0.023s. Yes, our application doesn’t have much, but still pretty impressive. Even for real applications, you will see startup times in the order of milliseconds. You can learn more about GraalVM on their website.

Developer Productivity

We have seen that Quarkus could help your company become Cloud Native. Awesome. But what about the developer? We all like new shiny things, and we are also super lazy. What does Quarkus do for the developer that cannot be done with other technologies?

Well, how about hot reloading that actually works without using external tools or complicated tricks? Yes, it is true. After 25 years, since Java was born, we now have a reliable way to change our code and see those changes with a simple refresh. Again, this is accomplished by the way Quarkus works internally. Everything is just code, so you don’t have to worry about the things that made hot reloading difficult anymore. It is a trivial operation.

To accomplish this, you have to run Quarkus in Development Mode. Just run mvn quarkus:dev and you are good to go. Quarkus will start up and you are free to do the changes to your code and immediately see them. For instance, you can change your REST endpoint parameters, add new methods, and change paths. Once you invoke them, they will be updated reflecting your code changes. How cool is that?

Is Quarkus Production Ready?

All of this seems to be too good to be true, but is Quakus actually ready for production environments? Yes it is.

A lot of companies are already adopting Quarkus as their development/runtime environment. Quarkus has a very fast release cadence (every few weeks), and a strong Open Source community that helps every developer in the Java community, whether they are just  getting started with Quarkus or are an advanced user.

Check out this sample application that you can download or clone. You can also read some of the adoption stories in a few blog posts so you can have a better idea of user experiences when using Quarkus.


After a year of its official announcement, Quarkus is already on version 1.3.1.Final. A lot of effort is being put in the project to help companies and developers to write applications that they can run natively in the Cloud.

We don’t know how far Quarkus can go, but one thing is for certain: Quarkus shook the entire Java ecosystem in a space dominated by Spring. I think the Java ecosystem can only win by having multiple offerings that can push each other and innovate to keep themselves competitives.


About the Author

Roberto Cortez is a passionate Java Developer with more than 10 years of experience. He is involved in the Open Source Community to help other individuals spread the knowledge about Java technologies. He is a regular speaker at conferences like JavaOne, Devoxx, Devnexus, JFokus, and others. He leads the Coimbra JUG and founded the JNation Conference in Portugal. When he is not working, he hangs out with friends, plays computer games, and spends time with family.

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