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Java2Days Sofia: Get your hands dirty with Quarkus

This repository contains all the code and assets that was written during the presentation.

Table of contents

  • Requirements: What you need before we start.
  • Assets: Scripts and manifests to setup services we are going to use.
  • Walkthrough: The steps we are going to follow.
  • Milestones: Links to snapshots/milestones of this presentation.


To use this material you need to have setup the following:

  • Docker & Docker compose (local docker daemon)

    • Images (for a smoother experience, please get the images prior to the lab):
      • debian:jessie-slim
      • postgres:10.5
      • fabric8/java-alpine-openjdk8-jre
      • strimzi/kafka:0.11.3-kafka-2.1.0
  • Java 1.8+

  • Maven (3.5.3+)

  • Graal (used GraalVM CE 19.2.1)

Nice to have

The following are optional requirements, that are considered nice to have.



SQL scripts for creating a greetings database. Shell scripts for starting and initializing the greetings database via docker.

To start the database:

cd assets/postgres


Docker compose manifest for starting a zookeepr/kafka cluster on docker.

To start kafka just connect:

cd assets/kafa
docker-compose up


Hello world

Let's create a simple Hello World web application!

Create a project from the shell using:

mvn io.quarkus:quarkus-maven-plugin:1.0.1.Final:create -DprojectGroupId=org.acme -DprojectArtifactId=hello-world -DprojectVersion=0.1-SNAPSHOT -Dendpoint=/hello -DclassName=org.acme.Hello

Open the project and find (which defines a JAX-RS resource) to get a glimpse. From the shell run the application in dev mode:

mvn compile quarkus:dev

Perform changes to the greeting message and demostrate how dev mode performs changes live, with no rebuilding involved. From this point on, either align unit tests, or toggle unit tests off -DskipTests.

Demonstrate native build.

mvn clean package -Pnative

Run the native application.


While the application is still running, from another shell check memory consumption:

ps ax -o pid,rss,command | numfmt --header --from-unit=1024 --to=iec --field 2 | grep -v grep | grep hello

At this point the result should be somewhere around 19M to 21M.

Fun with docker

To emphasize that native binaries need no jvm, change the base image of Dockerfile.native to use a minimal glibc based image. debian:jessie-slim is a good example.

Build the image.

 docker build -f src/main/docker/Dockerfile.native -t iocanel/hello-world:0.1-SNAPSHOT .

Run the container.

docker run -it -p 8080:8080 iocanel/hello-world:0.1-SNAPSHOT

Show that the application is running as expected.

Externalize Properties

Optionally, create a GreetingService annotated with javax.enterprise.context.ApplicationScoped and inject it into Hello resource. Add a @ConfigProperty(name="message") annotation onto a String property and create a method that returns that. In the Hello JAX-RS resource, change the hello method so that it calls this method. Open and add the value for message.


From the command line add the reactive stream operators extension.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-smallrye-reactive-streams-operators"

Create a StreamingGreetingService and inject it into Hello resource. Add a String array with greeting messages. Create a method that returns a Publisher<String> and internally uses Flowable.interval to return a random greeing message at the specified interval.

String[] greetings = new String[]{"Hola!", "Hi!", "Ciao!", "Bounjour!"};
Random random = new Random();
return Flowable.interval(5, TimeUnit.SECONDS).map(t -> greetings[random.nextInt(greetings.length)]);

Back to the Hello resource. Create a method like hello, for example called stream that uses a differnt path, say @Path("/stream") and insted of TEXT_PLAIN returns SERVER_SENT_EVENTS. This method should now delegate to the injected StreamingGreetingService. When the /stream path in hit in the browser, a new message will be added every 5 seconds.

Use reactive postgres client.

From the command line add the reactive stream operators extension.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-reactive-pg-client"

Ensure that postgres is up an running (see Assets). The database defines a greeting table that contains two fields, lang and greeting. Our goal is to obtain the value of the later for a given value of the former, but in a reactive way.

Create a PgGreetingService that injects a io.reactiverse.axle.pgclient.PgPool. Create a method that runs a simple query like select * from greeting where lang='it'. From the result get the greeting column and return that. The method should return CompletionStage<String>.

client.query("select * from greeting where lang='it'").thenApply(rs->rs.iterator().next().getString("greeting"));

As before inject the PgGreetingService into the Hello and create a different endpoint. In the the following properties are required:


Use Hibernate ORM

NOTE: Hibernate ORM conflicts with reactive postgres, so start by removing that dependency and code.

Add hibernate-orm and jdbc-postgres extensions.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-hibernate-orm"
mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-jdbc-postgresql"

Create a JPA entity named Greeting containing id (of type Long), greeting and lang fields (both of type String). This entity must be annotated with javax.persistence.Entity. Furthermore, getters and setters need to be added. Create a JpaGreetingService that injects the Entitymanager and performs a query by id.


Finally, inject the JpaGreetingService into Hello and create a new endpoint to show how it works.

Use Hibernate ORM Panache

Add hibernate-orm-panace extensions.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-hibernate-orm-panache"

Create a new entity named PanacheGreeting. The class needs to extend io.quarkus.hibernate.orm.panache.PanacheEntity. Furthermore, the class needs to be annotated with @Entity and @Table("greeting") (in order to map to the proper database table).

Add two non private fields greeting and lang. No constructors, getters or setters are required.

Create a new PanacheGreetingService to demonstrate the panache style of ORM.

PanacheGreeting pg = PanacheGreeting.findById(4L);
return pg.greeting;

NOTE: You cannot use a one liner for the above as findById returns a parameterized type and the actual return type needs to be inferred.

Inject the service into hello and create a new endpoint.

Use Spring Data

Add quarkus-spring-web and quarkus-spring-jpa to your project.

Create a org.springframework.web.bind.annotation.RestController with org.springframework.web.bind.annotation.RequestMapping to /spring Add a method with org.springframework.web.bind.annotation.GetMapping /hello.

Create new for our Greeting entity.

Create a new org.springframework.stereotype.Service that has @Autowired the greeting repository. This class should provide a method that returns the greeting based on id (see findById).

Inject the service into the controller and have the hello method delegate to the service.

mvn clean quarkus:dev

Open your browser to /spring/hello.

Use the rest-client to talk to the application we just created

Create a new application, say hello-cloud.

mvn io.quarkus:quarkus-maven-plugin:1.0.1.Final:create -DprojectGroupId=org.acme -DprojectArtifactId=hello-cloud -DprojectVersion=0.1-SNAPSHOT -Dendpoint=/hello -DclassName=org.acme.Hello

The application is meant to talk with hello-world that was created in the previous step.

We are going to need the rest-client and fault tolerance extensions from smallrye.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-smallrye-rest-client"
mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-smallrye-fault-tolerance"

Create a new HelloRestClient that has a hello method with path /hello (same as our hello-world application). In the RegisterRestClient annotation pass the baseUri pointing to the hello-world application.

For example:


Explain how to externalize this to

<class name>/mp-rest/url=<actual url>

Create a HelloRestService that inject the rest client. Add a greet method to the service that delegates to the rest client. Add the @Fallback annotation on the method and also add a fallback method.


Inject and use the service in the (as we've done many times).

Run the application.

 mvn clean compile quarkus:dev

Show normal request. Shutdown hello-world to demonstrate fallback.

Create a twiter to kafka application

NOTE: If you don't have a twitter developer account (requires access tokens and consumer keys), you may skip this step.

Create a new application, say tweet-writer.

mvn io.quarkus:quarkus-maven-plugin:1.0.1.Final:create -DprojectGroupId=org.acme -DprojectArtifactId=tweet-writer -DprojectVersion=0.1-SNAPSHOT

Open the project.

Add the smallrye-reactive-messaging-kafka extension.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-smallrye-reactive-messaging-kafka"

Manually add twitter4j dependency:


Create an application scoped class, that defines a method that returns a Publisher<String>. The method should use Flowable.create to caputre the tweets of interest.

public Publisher<String> stream() {
    return Flowable.create(s -> {
        final TwitterStream twitter = new TwitterStreamFactory().getInstance();
        twitter.addListener(new StatusAdapter() {
            public void onStatus(Status status) {
    }, BackpressureStrategy.DROP);

Where filter is an externalized property with the twitter fileter (e.g. QuarkusIO).

Open application.propeties to define the out-tweet sink.


Create a new resource and specify the twitter oauth configuration.


Ensure that kafka is running (see Assets). Run the application preferably overriding the port (as we are going to start multiple apps).

 mvn clean package
 java -jar target/*-runner.jar -Dquarkus.http.port=8081 -Dtwitter.filter=QuarkusIO

Create a kafka to browser application to display tweets via SSE.

Create a new application, say tweet-reader.

mvn io.quarkus:quarkus-maven-plugin:1.0.1.Final:create -DprojectGroupId=org.acme -DprojectArtifactId=tweet-reader -DprojectVersion=0.1-SNAPSHOT -Dendpoint=/hello -DclassName=org.acme.Hello

Open the project.

Add the smallrye-reactive-messaging-kafka extension.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-smallrye-reactive-messaging-kafka"

Open the Hello resource and Inject the source stream:

Publisher<String> tweets;

Create a method that produces server sent events and just return the tweets.

Configure kafka in the

NOTE: Users that skipped the previous step (due to lack of twitter dev account) will be provided access to an external kafka.<external kafka socket>

Run the application

 mvn compile quarkus:dev

Open localhost:8080/hello and watch the tweets as they appear.

Deploy to Kubernetes

The application can be deployed as is without deploying and configuring a database on Kubernetes. The simple /hello and /hello/stream endpoint will still work without issues (The ones that do require a database, of course won't work)

Add the kubernetes extension.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-kubernetes"

Build the application.

mvn clean install

Perform docker build and push (to dockerhub).

 docker build -f src/main/docker/Dockerfile.native -t iocanel/hello-world:0.1-SNAPSHOT .
 docker push iocanel/hello-world:0.1-SNAPSHOT

Open the generated manifest target/wiring-classes/META-INF/kubernetes/kubernetes.yml.

Apply the generated resources.

kubectl create -f target/wiring-classes/META-INF/kubernetes/kubernetes.yml

Expose the application to the real world, either by Ingress or Route (if used on Openshift).

Show the /hello is working as expected.

Remote dev mode on Kubernetes

Open the hello-world application.

Add the undertow-websockets extension.

mvn quarkus:add-extension -Dextensions="io.quarkus:quarkus-undertow-websockets"

Open the application.propeties so that we can specify the live reload password.

Create Dockerfile.remote so that we have a container capable of building quarkus that includes project sources:

FROM fabric8/java-centos-openjdk8-jdk
ENV JAVA_OPTIONS=" -Djava.util.logging.manager=org.jboss.logmanager.LogManager"
ENV AB_ENABLED=jmx_exporter
COPY mvnw /deployments/mvnw
COPY .mvn /deployments/.mvn
COPY src /deployments/src
COPY pom.xml /deployments/pom.xml

WORKDIR /deployments
USER root
RUN chown -R jboss src
USER jboss
ENTRYPOINT [ "./mvnw", "compile", "quarkus:dev" ]

Build the Dockerfile:

 docker build -f src/main/docker/Dockerfile.remote -t iocanel/hello-world:0.1-SNAPSHOT .

Push the image:

 docker push iocanel/hello-world:0.1-SNAPSHOT

Edit the deploynent and change image pull policy from IfNotPresent to Always.

Once the application running on kubernets is restarted. From the project run remote-dev and pass the url of the application.

mvn quarkus:remote-dev

Perform changes to the message and demonstrate them being applied live!



Quarkus deep dive lab for Java2Days 2019






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