Example: How to map Integer, String, and Boolean types

In this example, we’re going to create a very simple REST CRUD application in Quarkus and configure Integer, String and boolean properties into our applications.

Sometimes, this is a challenging use case because most of the Kubernetes resources and System properties only support String/text properties.

Prerequisites

  • Maven 3.8+

  • Java 17+

  • Have logged into a Kubernetes cluster

  • Have installed the Helm command line

Create application

Our application will print a hello message with the string, integer, and boolean config properties. We’ll only need the following extensions:

Let’s create our application from scratch:

mvn io.quarkus.platform:quarkus-maven-plugin:3.5.2:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=example \
    -Dextensions="resteasy-reactive,kubernetes-config"
cd example

The generated application will contain the following Hello resource:

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

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

    @ConfigProperty(name = "hello.message")
    String message;

    @ConfigProperty(name = "hello.number")
    int number;

    @ConfigProperty(name = "hello.flag")
    boolean flag;

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello() {
        return message + ", number=" + number + ", flag=" + flag;
    }
}

Next, we need to provide the actual properties via the application.properties file:

hello.message=Hello from application.properties
hello.number=1
hello.flag=true

Now, if we run our application and call our service via http://localhost:8080/hello, it will return Hello from application.properties, number=1, flag=true.

How can we configure Quarkus Helm to map the hello properties and update them when installing the generated Helm chart?

One way is using System properties, however this only supports String. If we map the above properties using system properties as described in the Mapping System Properties section:

hello.message=${helloMessage}
hello.number=${helloNumber}
hello.flag=${helloFlag}

When installing the Helm chart, this would fail because the hello.number and hello.flag properties are Strings. This is because internally Quarkus Helm is mapping the helloMessage system property as container environment properties which only supports String types.

Then, how can we do it? Quarkus Kubernetes Config to the rescue!

Let’s add a ConfigMap resource in src/main/kubernetes/kubernetes.yml:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  hello.message: Hello from configmap
  hello.number: 2
  hello.flag: false

The Quarkus Kubernetes extension will incorporate this ConfigMap resource in the generated resources at target/kubernetes/kubernetes.yml.

Next, we need to configure Quarkus to read this ConfigMap resource when starting the application in Kubernetes:

quarkus.kubernetes-config.enabled=true
quarkus.kubernetes-config.config-maps=app-config

As it is, if we build our application and install the Helm chart in Kubernetes, when calling the Hello endpoint, it would return: Hello from configmap, number=2, flag=false.

So good so far! Next, we can map the ConfigMap values into the Helm Chart values, so we can update these properties when installing the Helm chart. We can do this by adding the following properties:

# Map values in ConfigMap
quarkus.helm.values.message.paths=(kind == ConfigMap).data.'hello.message'
quarkus.helm.values.number.paths=(kind == ConfigMap).data.'hello.number'
quarkus.helm.values.number.value-as-int=1 (1)
quarkus.helm.values.flag.paths=(kind == ConfigMap).data.'hello.flag'
quarkus.helm.values.flag.value-as-bool=true (2)
1 Since the default value type for ConfigMap is still a string, we need to let the Quarkus Helm extension that the actual type is an integer using the value-as-int property.
2 And the same with the flag property. We need to instruct the Quarkus Helm extension that the actual type for the flag field is a boolean using value-as-bool.

Finally, after building our application, we can install the Helm chart and configure the Hello properties with the right types. For example, installing the chart as follows:

helm install quarkus target/helm/kubernetes/example --set app.number=3 --set app.flag=true --set app.message="Hello from helm"

And calling the service again, it would return Hello from helm, number=3, flag=true.

Happy coding!