Micronaut: Define immutable configuration using @ConfigurationInject annotation

We can define an immutable configuration by defining a class and use the @ConfigurationInject annotation on a constructor of a @ConfigurationProperties or @EachProperty bean.

 

Example

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

    private final String name;
    private final String version;
    private final String description;

    @ConfigurationInject
    public AppConfig(@Nonnull String name, String version,
            @Bindable(defaultValue = "chat server send and receive messages") String description) {
        this.name = name;
        this.version = version;
        this.description = description;
    }

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

 

Find the below working application.

 

Step 1: Create new maven project ‘micronaut-immutable-configuration-inject’.

 

Step 2: Update pom.xml with maven dependencies.

 

pom.xml

 

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.sample.app</groupId>
  <artifactId>micronaut-immutable-configuration-inject</artifactId>
  <version>0.1</version>
  <packaging>jar</packaging>

  <parent>
    <groupId>io.micronaut</groupId>
    <artifactId>micronaut-parent</artifactId>
    <version>3.7.3</version>
  </parent>

  <properties>
    <packaging>jar</packaging>
    <jdk.version>11</jdk.version>
    <release.version>11</release.version>
    <micronaut.version>3.7.3</micronaut.version>
    <micronaut.runtime>netty</micronaut.runtime>
    <exec.mainClass>com.sample.app.App</exec.mainClass>
  </properties>

  <repositories>
    <repository>
      <id>central</id>
      <url>https://repo.maven.apache.org/maven2</url>
    </repository>
  </repositories>

  <dependencies>
    <dependency>
      <groupId>io.micronaut</groupId>
      <artifactId>micronaut-inject</artifactId>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>io.micronaut</groupId>
      <artifactId>micronaut-validation</artifactId>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>io.micronaut</groupId>
      <artifactId>micronaut-http-client</artifactId>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>io.micronaut</groupId>
      <artifactId>micronaut-http-server-netty</artifactId>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>io.micronaut</groupId>
      <artifactId>micronaut-jackson-databind</artifactId>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>jakarta.annotation</groupId>
      <artifactId>jakarta.annotation-api</artifactId>
      <scope>compile</scope>
    </dependency>
    <dependency>
      <groupId>ch.qos.logback</groupId>
      <artifactId>logback-classic</artifactId>
      <scope>runtime</scope>
    </dependency>
    <dependency>
      <groupId>io.micronaut.test</groupId>
      <artifactId>micronaut-test-junit5</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-api</artifactId>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-engine</artifactId>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>io.micronaut.build</groupId>
        <artifactId>micronaut-maven-plugin</artifactId>
      </plugin>
      
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <!-- Uncomment to enable incremental compilation -->
          <!-- <useIncrementalCompilation>false</useIncrementalCompilation> -->

          <annotationProcessorPaths combine.children="append">
            <path>
              <groupId>io.micronaut</groupId>
              <artifactId>micronaut-http-validation</artifactId>
              <version>${micronaut.version}</version>
            </path>
          </annotationProcessorPaths>
         
        </configuration>
      </plugin>
    </plugins>
  </build>

</project>

 

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

 

application.yml

logger:
  levels:
    io.netty: ERROR
    io.micronaut: ERROR

my:
  app:
    name: chat server
    version: 1.23.45

 

Step 4: Define AppConfig class.

 

AppConfig.java

 

package com.sample.app.configuration;

import io.micronaut.context.annotation.ConfigurationInject;
import io.micronaut.context.annotation.ConfigurationProperties;
import io.micronaut.core.annotation.NonNull;
import io.micronaut.core.bind.annotation.Bindable;

@ConfigurationProperties("my.app")
public class AppConfig {
  private final String name;
  private final String version;
  private final String description;

  @ConfigurationInject
  public AppConfig(@NonNull String name, String version,
      @Bindable(defaultValue = "chat server send and receive messages") String description) {
    this.name = name;
    this.version = version;
    this.description = description;
  }

  public String getName() {
    return name;
  }

  public String getVersion() {
    return version;
  }

  public String getDescription() {
    return description;
  }

}

 

Step 5: Define main application class.

 

App.java

 

package com.sample.app;

import com.sample.app.configuration.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);
      System.out.println("name : " + appConfig.getName());
      System.out.println("version : " + appConfig.getVersion());
      System.out.println("description : " + appConfig.getDescription());
    }

  }
}

 

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-immutable-configuration-inject-0.1.jar’ in project target folder.

$ ls ./target/
classes
generated-sources
generated-test-sources
maven-archiver
maven-status
micronaut-immutable-configuration-inject-0.1.jar
original-micronaut-immutable-configuration-inject-0.1.jar
test-classes

 

Execute below command to run the application.

java -jar ./target/micronaut-immutable-configuration-inject-0.1.jar

 

You will see below messages in the console.

name : chat server
version : 1.23.45
description : chat server send and receive messages

 

You can download this application from this link.

 

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