Micronaut: configure properties using @ConfigurationProperties annotation

@ConfigurationProperties annotation defines a singleton bean whose property values are resolved from a PropertyResolver.

 

For example, application.yml file is defined like below.

 

application.yml

my:
  app:
    version: 1.23.45
    description:  application send and receive messages.

 

Now we can map the application configuration to a bean using @ConfigurationProperties annotation.

@ConfigurationProperties("my.app")
public class AppConfig {

	private String name = "my chat server";

	private String description;

	@Nonnull
	private String version;

	..........
	..........
}

From the above snippet, you can notice

a.   The @ConfigurationProperties annotation takes the configuration prefix (my.app)

b.   You can use javax.validation annotations to validate the configuration (@Nonnull)

c.    Default values can be assigned to the property (name = "my chat server")

 

Find the below working application.

 

Step 1: Create new maven project ‘micronaut-configuration-properties-annotaiton’.

 

Step 2: Update pom.xml with maven dependencies.

 

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.sample.app</groupId>
	<artifactId>micronaut-configuration-properties-annotaiton</artifactId>
	<version>1</version>

	<properties>
		<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
		<micronaut.version>3.7.3</micronaut.version>
		<slf4j.version>2.0.3</slf4j.version>
		<maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>

		<maven.compiler.target>15</maven.compiler.target>
		<maven.compiler.source>15</maven.compiler.source>
	</properties>

	<dependencies>

		<dependency>
			<groupId>io.micronaut</groupId>
			<artifactId>micronaut-inject-java</artifactId>
			<version>${micronaut.version}</version>
		</dependency>

		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>${slf4j.version}</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-simple</artifactId>
			<version>${slf4j.version}</version>
		</dependency>

	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>${maven-compiler-plugin.version}</version>
				<configuration>
					<annotationProcessorPaths>
						<path>
							<groupId>io.micronaut</groupId>
							<artifactId>micronaut-inject-java</artifactId>
							<version>${micronaut.version}</version>
						</path>
					</annotationProcessorPaths>
				</configuration>
			</plugin>

			<plugin>
				<artifactId>maven-assembly-plugin</artifactId>
				<configuration>
					<archive>
						<manifest>
							<mainClass>com.sample.app.App</mainClass>
						</manifest>
					</archive>
					<descriptorRefs>
						<descriptorRef>jar-with-dependencies</descriptorRef>
					</descriptorRefs>
				</configuration>

				<executions>
					<execution>
						<id>make-assembly</id>
						<phase>package</phase>
						<goals>
							<goal>single</goal>
						</goals>
					</execution>
				</executions>
			</plugin>

		</plugins>
	</build>
</project>

Step 3: Create application.yml file under src/main/resources folder.

 

application.yml

my:
  app:
    version: 1.23.45
    description:  application send and receive messages.

Step 4: Define AppConfig class.

 

AppConfig.java

package com.sample.app.configs;

import io.micronaut.context.annotation.ConfigurationProperties;
import jakarta.annotation.Nonnull;

@ConfigurationProperties("my.app")
public class AppConfig {

	private String name = "my chat server";

	private String description;

	@Nonnull
	private String version;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	public String getVersion() {
		return version;
	}

	public void setVersion(String version) {
		this.version = version;
	}

}

Step 5: Define main application class.

 

App.java

package com.sample.app;

import com.sample.app.configs.AppConfig;

import io.micronaut.context.ApplicationContext;

public class App {

	public static void main(String[] args) {

		try (ApplicationContext applicationContext = ApplicationContext.run()) {

			AppConfig appConfig = applicationContext.getBean(AppConfig.class);

			String appName = appConfig.getName();
			String version = appConfig.getVersion();
			String description = appConfig.getDescription();

			System.out.println("appName : " + appName);
			System.out.println("version : " + version);
			System.out.println("description : " + description + "\n");

		}

	}
}

Total project structure looks like below.

Build the project using mvn package command.

Navigate to the folder where pom.xml is located and execute the command ‘mvn package’.

 

Upon command successful execution, you can see the jar file ‘micronaut-configuration-properties-annotaiton-1-jar-with-dependencies.jar’ in project target folder.

$ ls ./target/
archive-tmp
classes
generated-sources
generated-test-sources
maven-archiver
maven-status
micronaut-configuration-properties-annotaiton-1-jar-with-dependencies.jar
micronaut-configuration-properties-annotaiton-1.jar
test-classes

Execute below command to run the application.

$ java -jar ./target/micronaut-configuration-properties-annotaiton-1-jar-with-dependencies.jar
appName : my chat server
version : 1.23.45
description : application send and receive messages

You can download this application from this link.

 

 

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