# Accessing application properties with Spring Boot properties API

If you prefer to use Spring Boot `@ConfigurationProperties` annotated class to access application properties instead of `@ConfigMapping` or a MicroProfile `@ConfigProperty` approach, you can do that with this extension.

| Spring Boot `@ConfigurationProperties` has a few limitations. For instance, `Map` injection is not supported. Consider using Mapping configuration to objects.

## Prerequisites

To complete this guide, you need:

- Roughly 15 minutes

- An IDE

- JDK 17+ installed with `JAVA_HOME` configured appropriately

- Apache Maven 3.9.9

- 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. 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 `spring-boot-properties-quickstart` directory.

## Creating the Maven project

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

CLI

    quarkus create app org.acme:spring-boot-properties-quickstart \
        --extension='rest,spring-boot-properties' \
        --no-code
    cd spring-boot-properties-quickstart

To create a Gradle project, add the `--gradle` or `--gradle-kotlin-dsl` option.

For more information about how to install and use the Quarkus CLI, see the Quarkus CLI guide.

Maven

    mvn io.quarkus.platform:quarkus-maven-plugin:3.26.0.CR1:create \
        -DprojectGroupId=org.acme \
        -DprojectArtifactId=spring-boot-properties-quickstart \
        -Dextensions='rest,spring-boot-properties' \
        -DnoCode
    cd spring-boot-properties-quickstart

To create a Gradle project, add the `-DbuildTool=gradle` or `-DbuildTool=gradle-kotlin-dsl` option.

For Windows users:

- If using cmd, (don’t use backward slash `\` and put everything on the same line)

- If using Powershell, wrap `-D` parameters in double quotes e.g. `"-DprojectArtifactId=spring-boot-properties-quickstart"`

This command generates a project and imports the `spring-boot-properties` extension.

If you already have your Quarkus project configured, you can add the `spring-boot-properties` extension to your project by running the following command in your project base directory:

CLI

    quarkus extension add spring-boot-properties

Maven

    ./mvnw quarkus:add-extension -Dextensions='spring-boot-properties'

Gradle

    ./gradlew addExtension --extensions='spring-boot-properties'

This will add the following to your build file:

pom.xml

    <dependency>
        <groupId>io.quarkus</groupId>
        <artifactId>quarkus-spring-boot-properties</artifactId>
    </dependency>

build.gradle

    implementation("io.quarkus:quarkus-spring-boot-properties")

## GreetingController

First, create a `GreetingResource` Jakarta REST resource in the `src/main/java/org/acme/spring/boot/properties/GreetingResource.java` file that looks like:

    package org.acme.spring.boot.properties;

    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 {

        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String hello() {
            return "hello";
        }
    }

## Injecting properties

Create a new class `src/main/java/org/acme/spring/boot/properties/GreetingProperties.java` with a message field:

    package org.acme.spring.boot.properties;

    import org.springframework.boot.context.properties.ConfigurationProperties;

    @ConfigurationProperties("greeting")
    public class GreetingProperties {

        public String text;
    }

Here `text` field is public, but it could also be a private field with getter and setter or just a public getter in an interface. Because `text` does not have a default value it is considered required and unless it is defined in a configuration file (`application.properties` by default) your application will fail to start. Define this property in your `src/main/resources/application.properties` file:

    # Your configuration properties
    greeting.text=hello

Now modify `GreetingResource` to start using the `GreetingProperties`:

    package org.acme.spring.boot.properties;

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

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

        @Inject
        GreetingProperties properties;

        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String hello() {
            return properties.text;
        }
    }

Run the tests to verify that application still functions correctly.

## Package and run the application

Run the application in dev mode with:

CLI

    quarkus dev

Maven

    ./mvnw quarkus:dev

Gradle

    ./gradlew --console=plain quarkusDev

Open your browser to http://localhost:8080/greeting.

Changing the configuration file is immediately reflected.

As usual, the application can be packaged using:

CLI

    quarkus build

Maven

    ./mvnw install

Gradle

    ./gradlew build

And executed using `java -jar target/quarkus-app/quarkus-run.jar`.

You can also generate the native executable with:

CLI

    quarkus build --native

Maven

    ./mvnw install -Dnative

Gradle

    ./gradlew build -Dquarkus.native.enabled=true

## Default values

Now let’s add a suffix for a greeting for which we’ll set a default value.

Properties with default values can be configured in a configuration file just like any other property. However, the default value will be used if the property was not defined in a configuration file.

Go ahead and add the new field to the `GreetingProperties` class:

    package org.acme.spring.boot.properties;

    import org.springframework.boot.context.properties.ConfigurationProperties;

    @ConfigurationProperties("greeting")
    public class GreetingProperties {

        public String text;

        public String suffix = "!";
    }

And update the `GreetingResource` and its test `GreetingResourceTest`:

    package org.acme.spring.boot.properties;

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

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

        @Inject
        GreetingProperties properties;

        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String hello() {
            return properties.text + properties.suffix;
        }
    }

    package org.acme.spring.boot.properties;

    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!"));
        }
    }

Run the tests to verify the change.

## Optional values

Properties with optional values are the middle-ground between standard and properties with default values. While a missing property in a configuration file will not cause your application to fail, it will nevertheless not have a value set. We use `java.util.Optional` type to define such properties.

Add an optional `name` property to the `GreetingProperties`:

    package org.acme.spring.boot.properties;

    import java.util.Optional;

    import org.springframework.boot.context.properties.ConfigurationProperties;

    @ConfigurationProperties("greeting")
    public class GreetingProperties {

        public String text;

        public String suffix = "!";

        public Optional<String> name;
    }

And update the `GreetingResource` and its test `GreetingResourceTest`:

    package org.acme.spring.boot.properties;

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

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

        @Inject
        GreetingProperties properties;

        @GET
        @Produces(MediaType.TEXT_PLAIN)
        public String hello() {
            return properties.text + ", " + properties.name.orElse("You") + properties.suffix;
        }
    }

    package org.acme.spring.boot.properties;

    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, You!"));
        }
    }

Run the tests to verify the change.

## Grouping properties

Now we have three properties in our `GreetingProperties` class. While `name` could be considered more of a runtime property (and maybe could be passed as an HTTP query parameter in the future), `text` and `suffix` are used to define a message template. Let’s group these two properties in a separate inner class:

    package org.acme.spring.boot.properties;

    import java.util.Optional;

    import org.springframework.boot.context.properties.ConfigurationProperties;

    @ConfigurationProperties("greeting")
    public class GreetingProperties {

        public Message message;

        public Optional<String> name;

        public static class Message {

            public String text;

            public String suffix = "!";
        }
    }

Here `Message` properties class is defined as an inner class, but it could also be a top level class.

Having such property groups brings more structure to your configuration. This is especially useful when then number of properties grows.

Because of the additional class, our property names have changed. Let’s update the properties file and the `GreetingResource` class.

    # Your configuration properties
    greeting.message.text=hello

    package org.acme.spring.boot.properties;

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

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

        @Inject
        GreetingProperties properties;

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

## More Spring guides

Quarkus has more Spring compatibility features. See the following guides for more details:

- Quarkus - Extension for Spring DI

- Quarkus - Extension for Spring Web

- Quarkus - Extension for Spring Data JPA

- Quarkus - Extension for Spring Data REST

- Quarkus - Extension for Spring Security

- Quarkus - Reading properties from Spring Cloud Config Server

- Quarkus - Extension for Spring Cache

- Quarkus - Extension for Spring Scheduled