This guide explains how your Quarkus application can read configuration properties at runtime from the Spring Cloud Config Server.
Prerequisites
To complete this guide, you need:
-
Roughly 15 minutes
-
An IDE
-
JDK 11+ installed with
JAVA_HOMEconfigured appropriately -
Apache Maven 3.8.4
-
Optionally the Quarkus CLI if you want to use it
-
Optionally Mandrel or GraalVM installed and configured appropriately if you want to build a native executable (or Docker if you use a native container build)
Solution
We recommend that you follow the instructions in the next sections and create the application step by step.
Stand up a Config Server
To stand up the Config Server required for this guide, please follow the instructions outlined here.
The end result of that process is a running Config Server that will provide the Hello world value for a configuration property named message when the application querying the server is named a-bootiful-client.
Creating the Maven project
First, we need a new project. Create a new project with the following command:
This command generates a project which imports the spring-cloud-config-client extension.
If you already have your Quarkus project configured, you can add the spring-cloud-config-client extension
to your project by running the following command in your project base directory:
quarkus extension add 'spring-cloud-config-client'./mvnw quarkus:add-extension -Dextensions="spring-cloud-config-client"./gradlew addExtension --extensions="spring-cloud-config-client"This will add the following to your build file:
<dependency>
<groupId>io.quarkus</groupId>
<artifactId>quarkus-spring-cloud-config-client</artifactId>
</dependency>implementation("io.quarkus:quarkus-spring-cloud-config-client")GreetingController
First, create a simple GreetingResource JAX-RS resource in the
src/main/java/org/acme/spring/cloud/config/client/GreetingResource.java file that looks like:
package org.acme.spring.spring.cloud.config.client;
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";
}
}As we want to use configuration properties obtained from the Config Server, we will update the GreetingResource to inject the message property. The updated code will look like this:
package org.acme.spring.spring.cloud.config.client;
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("/hello")
public class GreetingResource {
@ConfigProperty(name = "message", defaultValue="hello default")
String message;
@GET
@Produces(MediaType.TEXT_PLAIN)
public String hello() {
return message;
}
}Configuring the application
Quarkus provides various configuration knobs under the quarkus.spring-cloud-config root. For the purposes of this guide, our Quarkus application is going to be configured in application.properties as follows:
# use the same name as the application name that was configured when standing up the Config Server
quarkus.application.name=a-bootiful-client
# enable retrieval of configuration from the Config Server - this is off by default
quarkus.spring-cloud-config.enabled=true
# configure the URL where the Config Server listens to HTTP requests - this could have been left out since http://localhost:8888 is the default
quarkus.spring-cloud-config.url=http://localhost:8888Package and run the application
Run the application with:
quarkus dev./mvnw quarkus:dev./gradlew --console=plain quarkusDevOpen your browser to http://localhost:8080/greeting.
The result should be: Hello world as it is the value obtained from the Spring Cloud Config server.
Run the application as a native executable
You can of course create a native image using the instructions of the Building a native executable guide.