Application Configuration Guide

Hardcoded values in your code is a no go (even if we all did it at some point ;-)). In this guide, we learn how to configure your application.

Prerequisites

To complete this guide, you need:

  • between 5 and 10 minutes

  • an IDE

  • JDK 1.8+ installed with JAVA_HOME configured appropriately

  • Apache Maven 3.5.3+

Solution

We recommend that you follow the instructions in the next sections and create the application step by step. However, you can go right to the completed example.

Clone the Git repository: git clone https://github.com/quarkusio/quarkus-quickstarts.git, or download an archive.

The solution is located in the application-configuration directory.

Creating the Maven project

First, we need a new project. Create a new project with the following command:

mvn io.quarkus:quarkus-maven-plugin:0.15.0:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=application-configuration \
    -DclassName="org.acme.config.GreetingResource" \
    -Dpath="/greeting"

It generates:

  • the Maven structure

  • a landing page accessible on http://localhost:8080

  • example Dockerfile files for both native and jvm modes

  • the application configuration file

  • an org.acme.config.GreetingResource resource

  • an associated test

Injecting configuration value

Quarkus uses MicroProfile Config to inject the configuration in the application. The injection uses the @ConfigProperty annotation.

@ConfigProperty(name = "greeting.message")
String message;
Note
When injecting a configured value, you can use @Inject @ConfigProperty or just @ConfigProperty. The @Inject annotation is not necessary for members annotated with @ConfigProperty, a behavior which differs from MicroProfile Config

Edit the org.acme.config.GreetingResource, and introduce the following configuration properties:

@ConfigProperty(name = "greeting.message") (1)
String message;

@ConfigProperty(name = "greeting.suffix", defaultValue="!") (2)
String suffix;

@ConfigProperty(name = "greeting.name")
Optional<String> name; (3)
  1. If you do not provide a value for this property, the application startup fails with javax.enterprise.inject.spi.DeploymentException: No config value of type [class java.lang.String] exists for: greeting.message.

  2. The default value is injected if the configuration does not provide a value for greeting.suffix.

  3. This property is optional - an empty Optional is injected if the configuration does not provide a value for greeting.name.

Now, modify the hello method to use the injected properties:

@GET
@Produces(MediaType.TEXT_PLAIN)
public String hello() {
    return message + " " + name.orElse("world") + suffix;
}

Create the configuration

By default, Quarkus reads application.properties. Edit the src/main/resources/application.properties with the following content:

# Your configuration properties
greeting.message = hello
greeting.name = quarkus

Once set, check the application with:

$ curl http://localhost:8080/greeting
hello quarkus!
Tip
If the application requires configuration values and these values are not set, an error is thrown. So you can quickly know when your configuration is complete.

Update the test

We also need to update the functional test to reflect the changes made to endpoint. Edit the src/test/java/org/acme/config/GreetingResourceTest.java file and change the content of the testHelloEndpoint method to:

package org.acme.config;

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("/greeting")
          .then()
             .statusCode(200)
             .body(is("hello quarkus!")); // Modified line
    }

}

Package and run the application

Run the application with: ./mvnw compile quarkus:dev. Open your browser to http://localhost:8080/greeting.

Changing the configuration file is immediately reflected. You can add the greeting.suffix, remove the other properties, change the values, etc.

As usual, the application can be packaged using ./mvnw clean package and executed using the -runner.jar file. You can also generate the native executable with ./mvnw clean package -Pnative.

Overriding properties at runtime

Quarkus does much of its configuration and bootstrap at build time. Most properties will then be read and set during the build time step. To change them, make sure to repackage your application.

./mvnw clean package

Extensions do define some properties as overridable at runtime. A canonical example is the database URL, username and password which is only known specifically in your target environment. This is a tradeoff as the more runtime properties are available, the less build time prework Quarkus can do. The list of runtime properties is therefore lean.

You can override these runtime properties with the following mechanisms (in decreasing priority):

  1. using system properties:

    • for a runner jar: java -Dquarkus.datasource.password=youshallnotpass -jar target/myapp-runner.jar

    • for a native executable: ./target/myapp-runner -Dquarkus.datasource.password=youshallnotpass

  2. using environment variables:

    • for a runner jar: export QUARKUS_DATASOURCE_PASSWORD=youshallnotpass ; java -jar target/myapp-runner.jar

    • for a native executable: export QUARKUS_DATASOURCE_PASSWORD=youshallnotpass ; ./target/myapp-runner

Note
Environment variables names are following the conversion rules of Eclipse MicroProfile

Custom configuration sources

You can also introduce custom configuration sources in the standard MicroProfile Config manner. To do this, you must provide a class which implements either org.eclipse.microprofile.config.spi.ConfigSource or org.eclipse.microprofile.config.spi.ConfigSourceProvider. Create a service file for the class and it will be detected and installed at application startup.

More info on how to configure

Quarkus relies on Eclipse MicroProfile and inherit its features.

There are converters that convert your property file content from String to typed Java types. See the list in the specification.