Hello World - Java (Quarkus)

A simple JAX-RS REST API application that is written in Java and uses Quarkus.

This samples uses Docker to build locally. The app reads in a TARGET env variable and then prints “Hello World: ${TARGET}!”. If a value for TARGET is not specified, the “NOT SPECIFIED” default value is used.

Before you begin

You must meet the following requirements to run this sample:

Have a Kubernetes cluster running with the Knative Serving component installed. For more information, see the Knative instruction guides.
An installed version of the following tools:
A Docker Hub account to which you are able to upload your sample’s container image.

Getting the code

You can either clone a working copy of the sample code from the repository, or following the steps in the Recreating the sample code to walk through the steps of updating all the files.

Cloning the sample code

Use this method to clone and then immediate run the sample. To clone the sample code, run the following commands:

git clone -b "release-0.22" https://github.com/knative/docs.git knative/docs
cd knative/docs/community/samples/serving/helloworld-java-quarkus

You are now ready to run the sample locally.

Recreating the sample code

Use the following steps to obtain an incomplete copy of the sample code for which you update and create the necessary build and configuration files:

From the console, create a new empty web project using the Maven archetype commands:

mvn io.quarkus:quarkus-maven-plugin:0.13.3:create \
 -DprojectGroupId=com.redhat.developer.demos \
 -DprojectArtifactId=helloworld-java-quarkus \
 -DclassName="com.redhat.developer.demos.GreetingResource" \
 -Dpath="/"

Update the GreetingResource class in src/main/java/com/redhat/developer/demos/GreetingResource.java to handle the “/” mapping and also add a @ConfigProperty field to provide the TARGET environment variable:

package com.redhat.developer.demos;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import org.eclipse.microprofile.config.inject.ConfigProperty;

@Path("/")
public class GreeterResource {
  @ConfigProperty(name = "TARGET", defaultValue="World")
  String target;

  @GET
  @Produces(MediaType.TEXT_PLAIN)
  public String greet() {
    return "Hello " + target + "!";
  }
}

Update src/main/resources/application.properties to configuration the application to default to port 8080, but allow the port to be overridden by the PORT environmental variable:
```
# Configuration file
# key = value

quarkus.http.port=${PORT:8080}
```

Update src/test/java/com/redhat/developer/demos/GreetingResourceTest.java test to reflect the change:

package com.redhat.developer.demos;

import io.quarkus.test.junit.QuarkusTest;
import org.junit.jupiter.api.Test;

import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;

@QuarkusTest
public class GreetingResourceTest {

  @Test
  public void testHelloEndpoint() {
      given()
        .when().get("/")
        .then()
          .statusCode(200)
          .body(is("Hello World!"));
  }
}

Remove src/main/resources/META-INF/resources/index.html file since it’s unncessary for this example.
```
rm src/main/resources/META-INF/resources/index.html
```
Remove .dockerignore file since it’s unncessary for this example.
```
rm .dockerignore
```

In your project directory, create a file named Dockerfile and copy the code block below into it.

FROM quay.io/rhdevelopers/quarkus-java-builder:graal-1.0.0-rc15 as builder
COPY . /project
WORKDIR /project
# uncomment this to set the MAVEN_MIRROR_URL of your choice, to make faster builds
# ARG MAVEN_MIRROR_URL=<your-maven-mirror-url>
# e.g.
#ARG MAVEN_MIRROR_URL=http://192.168.64.1:8081/nexus/content/groups/public

RUN /usr/local/bin/entrypoint-run.sh mvn -DskipTests clean package

FROM fabric8/java-jboss-openjdk8-jdk:1.5.4
USER jboss
ENV JAVA_APP_DIR=/deployments

COPY --from=builder /project/target/lib/* /deployments/lib/
COPY --from=builder /project/target/*-runner.jar /deployments/app.jar

ENTRYPOINT [ "/deployments/run-java.sh" ]

If you want to build Quarkus native image, then copy the following code block in to file called Dockerfile.native

FROM quay.io/rhdevelopers/quarkus-java-builder:graal-1.0.0-rc15 as builder
COPY . /project
# uncomment this to set the MAVEN_MIRROR_URL of your choice, to make faster builds
# ARG MAVEN_MIRROR_URL=<your-maven-mirror-url>
# e.g.
# ARG MAVEN_MIRROR_URL=http://192.168.64.1:8081/nexus/content/groups/public

RUN /usr/local/bin/entrypoint-run.sh mvn -DskipTests clean package -Pnative

FROM registry.fedoraproject.org/fedora-minimal

COPY --from=builder /project/target/helloworld-java-quarkus-runner /app

ENTRYPOINT [ "/app" ]

Create a new file, service.yaml and copy the following service definition into the file. Make sure to replace {username} with your Docker Hub username.

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: helloworld-java-quarkus
spec:
  template:
    spec:
      containers:
        - image: docker.io/{username}/helloworld-java-quarkus
          env:
            - name: TARGET
              value: "Quarkus Sample v1"

Locally testing your sample

Run the application locally:
```
./mvnw compile quarkus:dev
```
Go to http://localhost:8080/ to see your Hello World! message.

Building and deploying the sample

Once you have recreated the sample code files (or used the files in the sample folder) you’re ready to build and deploy the sample app.

Use Docker to build the sample code into a container. To build and push with Docker Hub, run these commands replacing {username} with your Docker Hub username:

# Build the container on your local machine
docker build -t {username}/helloworld-java-quarkus .

# (OR)
# Build the container on your local machine - Quarkus native mode
docker build -t {username}/helloworld-java-quarkus -f Dockerfile.native .

# Push the container to docker registry
docker push {username}/helloworld-java-quarkus

After the build has completed and the container is pushed to docker hub, you can deploy the app into your cluster. Ensure that the container image value in service.yaml matches the container you built in the previous step. Apply the configuration using kubectl:
```
kubectl apply --filename service.yaml
```
Now that your service is created, Knative will perform the following steps:
- Create a new immutable revision for this version of the app.
- Network programming to create a route, ingress, service, and load balancer for your app.
- Automatically scale your pods up and down (including to zero active pods).

To find the URL for your service, use

kubectl get ksvc helloworld-java-quarkus

NAME                     URL
helloworld-java-quarkus  http://helloworld-java-quarkus.default.1.2.3.4.xip.io

Now you can make a request to your app and see the result. Replace the URL below with the URL returned in the previous command.
```
curl http://helloworld-java-quarkus.default.1.2.3.4.xip.io

Namaste Knative World!
```

Removing the sample app deployment

To remove the sample app from your cluster, delete the service record:

kubectl delete --filename service.yaml

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