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Java Quarkus Tutorial

Quarkus is a Kubernetes-native Java framework tailored for GraalVM and OpenJDK HotSpot. It is designed for building Java applications that are optimized for cloud environments and microservices architecture.

1. Prerequisites​

Before getting started with Quarkus, make sure you have the following installed:

Verify Installation​

To check your installations, run the following commands:

java -version
mvn -version

If you installed the Quarkus CLI:

quarkus version

2. Creating a New Quarkus Project​

You can create a new Quarkus project using the Quarkus CLI or Maven.

Using the Quarkus CLI​

Run the following command to create a new project:

quarkus create app org.acme:getting-started --no-code
cd getting-started

Using Maven​

Alternatively, you can use Maven to generate a new project:

mvn io.quarkus:quarkus-maven-plugin:2.4.2:create     -DgroupId=org.acme     -DartifactId=getting-started     -Dextensions="resteasy,resteasy-jackson"
cd getting-started

Project Structure​

After creating the project, the structure will look like this:

getting-started
├── src
│   ├── main
│   │   ├── java
│   │   └── resources
│   └── test
└── pom.xml

3. Developing Your First REST Endpoint​

Create a Resource Class​

Create a new Java class named GreetingResource.java in the src/main/java/org/acme directory:

package org.acme;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/hello")
public class GreetingResource {

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return "Hello, Quarkus!";
    }
}

Explanation​

  • @Path: Defines the URI path for the resource.
  • @GET: Indicates that this method responds to HTTP GET requests.
  • @Produces: Specifies the media type returned by the method.

4. Running Your Application​

You can run your Quarkus application in development mode using the following command:

./mvnw quarkus:dev

Accessing the Endpoint​

Once the application is running, open your web browser or a tool like curl to access the endpoint:

http://localhost:8080/hello

You should see the output:

Hello, Quarkus!

5. Adding Dependencies​

You can easily add extensions (dependencies) to your Quarkus project. For example, to add Hibernate ORM with Panache:

./mvnw quarkus:add-extension -Dextensions="hibernate-orm-panache"

Check Available Extensions​

You can see all available extensions by running:

./mvnw quarkus:list-extensions

6. Building the Application​

To build a production-ready package of your application, run:

./mvnw package

This will create a jar file in the target directory.

7. Deploying to Kubernetes​

Quarkus simplifies deployment to Kubernetes. You can build a Docker image with:

./mvnw clean package -Dquarkus.container-image.build=true

Deploying to Kubernetes​

You can use the Kubernetes CLI to deploy the generated Docker image:

kubectl apply -f src/main/kubernetes/kubernetes.yml

Ensure your kubernetes.yml file is configured correctly for your application.

8. Conclusion​

Quarkus is a powerful framework for building cloud-native Java applications. This tutorial covered the basics of setting up a Quarkus project, creating a simple REST endpoint, running the application, adding dependencies, and deploying it to Kubernetes.

Further Reading​

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