What is Quarkus?

Java has been around for more than 25 years now. It is one of the most used programming languages, especially for developing enterprise applications. Its rich ecosystem, extensive and open community, and “write once, run anywhere” approach, have made it the de facto choice for creating enterprise software for decades.

However, things are changing now. We are in the era of the cloud, Kubernetes, and container images. Things such as startup time or memory footprint, which were not that significant before, are becoming more relevant these days. Java is losing its pace compared to other languages, which are specifically tailored for these new environments.

Quarkus is a new Java framework that was first released in 2019. It provides similar features to those of other mainstream Java frameworks such as Spring Boot or Micronaut. The main goals of Quarkus are to improve the application’s startup time, its memory footprint, and the developer experience.

Quarkus was built from the ground up to be cloud-native from the start. Regardless of how you package your application, boot time, and memory consumption, Quarkus performs much better than the alternatives. That’s why Quarkus is also known as Supersonic Subatomic Java.

Quarkus is built on top of long-lived proven standards and libraries. When Quarkus was designed, the team decided to rely on existing tools, frameworks, and standards instead of building something new from scratch. This was done so that developers don’t have to spend time learning something new and can focus on building more performant applications instead, taking advantage of their experience.

Quarkus uses the Java Enterprise Edition (EE) Contexts and Dependency Injection (CDI) standard for dependency injection; MicroProfile, a community-driven specification to optimize Java EE for a microservice architecture and for configuration and monitoring; Java Persistence API (JPA) annotations to define the object-relational mapping (ORM); Jakarta RESTful Web Services (JAX-RS) annotations to define the REST controllers; and many more technologies in a long, ever-growing list.

Quarkus brings a new developer experience to Java. One of the main drawbacks of Java when compared to other languages is the traditionally slow development cycles. A simple change to a line of code usually involves recompiling, repackaging, and restarting the application. This process could take anywhere from seconds to minutes, completely reducing the developer’s productivity. Quarkus aims at fixing this pain point by providing live coding, a unified configuration, a developer UI, and many more tools to bring joy back to developers.

Quarkus combines the traditional imperative coding style with the cloud-native friendly reactive coding style approach. Regardless of the type of application you are building, Quarkus provides first-class support for both paradigms. The cloud has brought new architectures to our systems, whether microservices, serverless, or event-driven. In this book, we’ll explore the new reactive non-blocking style, which will bring massive performance improvements when compared to the more classic imperative approach.

Quarkus is a free open source project that was initially released in March 2019. It is not only a fast-growing project in terms of adoption, but its community is soaring too. Despite its youth, it already has around 600 contributors (at the time of writing) and a growing ecosystem of extensions (https://github.com/quarkiverse). There’s already an extensive list of publications and bibliography available too.

Quarkus makes it extremely easy to create native executables for your platform. The framework provides almost transparent integration with GraalVM, a high-performance Java Development Kit (JDK) distribution that allows you to compile your Java code into a standalone binary executable.