Add a Native Image Layers demo for a simple Micronaut application.

.github/workflows/microservices-micronaut-hello-rest-maven-layered.yml

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+name: microservices/micronaut-hello-rest-maven-layered
+on:
+  push:
+    paths:
+      - 'native-image/microservices/micronaut-hello-rest-maven-layered/**'
+      - '.github/workflows/microservices-micronaut-hello-rest-maven-layered.yml'
+  schedule:
+    - cron: "0 0 1 * *" # run every month
+  workflow_dispatch:
+permissions:
+  contents: read
+jobs:
+  run:
+    name: Run 'microservices/micronaut-hello-rest-maven-layered'
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    strategy:
+      matrix:
+        java-version: ['25']
+    steps:
+      - uses: actions/checkout@v4
+      - name: Download GraalVM 25.1 EA builds
+        run: curl -sL -o $RUNNER_TEMP/graalvm-jdk-25e1-linux-amd64.tar.gz https://github.com/graalvm/oracle-graalvm-ea-builds/releases/download/jdk-25e1-25.0.0-ea.01/graalvm-jdk-25e1-25.0.0-ea.01_linux-x64_bin.tar.gz
+      - uses: actions/setup-java@v4
+        with:
+          java-version: '25'
+          distribution: 'jdkfile'
+          jdkFile: ${{ runner.temp }}/graalvm-jdk-25e1-linux-amd64.tar.gz
+      - name: Run 'microservices/micronaut-hello-rest-maven-layered'
+        run: |
+          cd native-image/microservices/micronaut-hello-rest-maven-layered
+          ./run.sh

native-image/microservices/micronaut-hello-rest-maven-layered/.gitignore

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+Thumbs.db
+.DS_Store
+.gradle
+build/
+target/
+out/
+.micronaut/
+.idea
+*.iml
+*.ipr
+*.iws
+.project
+.settings
+.classpath
+.factorypath
+app-layer-target
+base-layer-target

native-image/microservices/micronaut-hello-rest-maven-layered/.mvn/wrapper/maven-wrapper.properties

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+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.10/apache-maven-3.9.10-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.1.1/maven-wrapper-3.1.1.jar

native-image/microservices/micronaut-hello-rest-maven-layered/README.md

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+# Micronaut Layered Native Image Demo
+
+This example shows how to build a simple [Micronaut](https://micronaut.io/) REST application using the [GraalVM Native Image Layers](https://github.com/oracle/graal/blob/master/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/imagelayer/NativeImageLayers.md) feature.
+
+### Prerequisites
+- SDKMAN! (for installing Micronaut CLI)
+- Latest GraalVM 25.1 EA build (with Native Image support)
+
+> Native Image Layers is an experimental feature. For the best experience use the latest [GraalVM Early Access Build](https://github.com/graalvm/oracle-graalvm-ea-builds/releases).
+
+## Environment Setup
+Point your `JAVA_HOME` to the GraalVM distribution.
+```bash
+export JAVA_HOME=/path/to/graalvm/ea/build
+```
+
+Install `mn`, the Micronaut CLI tool:
+```bash
+sdk install micronaut 4.9.4
+sdk use micronaut 4.9.4
+```
+
+## Create the Micronaut Application
+
+We'll start by generating a basic application using the Micronaut CLI.
+For more details, see the [Micronaut guide](https://guides.micronaut.io/latest/creating-your-first-micronaut-app-maven-java.html).
+
+```bash
+mn create-app example.micronaut.micronaut-hello-rest-maven-layered --build=maven --lang=java --features=graalvm
+```
+
+This creates a new Micronaut project with the following structure:
+```
+micronaut-hello-rest-maven-layered/
+├── pom.xml
+├── src/
+│   ├── main/
+│   │   ├── java/
+│   │   │   └── example/micronaut/Application.java
+│   │   └── resources/
+│   │       └── application.properties
+│   └── test/
+└── mvnw (Maven wrapper)
+```
+
+For executing the subsequent commnds we must enter the project directory:
+```bash
+cd micronaut-hello-rest-maven-layered
+```
+
+### Add A Custom Controller
+
+We'll add a custom controller to `src/main/java/example/micronaut/HelloController.java`:
+```java 
+package example.micronaut;
+
+import io.micronaut.http.MediaType;
+import io.micronaut.http.annotation.Controller;
+import io.micronaut.http.annotation.Get;
+import io.micronaut.http.annotation.Produces;
+
+@Controller("/hello") 
+public class HelloController {
+    @Get 
+    @Produces(MediaType.TEXT_PLAIN) 
+    public String hello() {
+        return "Hello from GraalVM Native Image!";
+    }
+}
+```
+
+### Standalone Application
+
+We'll first demonstrate how to build a standalone executable for this simple app.
+For this we'll extend the `pom.xml` with a custom profile and configure the native build using the [GraalVM Native Image Maven plugin](https://graalvm.github.io/native-build-tools/latest/maven-plugin.html):
+```xml
+<profile>
+    <id>standalone</id>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.graalvm.buildtools</groupId>
+                <artifactId>native-maven-plugin</artifactId>
+                <version>0.10.3</version>
+                <configuration>
+                    <imageName>standalone-app</imageName>
+                    <mainClass>example.micronaut.Application</mainClass>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</profile>
+```
+
+Using this profile we can now generate the executable:
+```bash
+./mvnw clean package -Dpackaging=native-image -Pstandalone
+```
+
+This will generate an executable file that we can run:
+```bash
+./target/standalone-app
+ __  __ _                                  _   
+|  \/  (_) ___ _ __ ___  _ __   __ _ _   _| |_ 
+| |\/| | |/ __| '__/ _ \| '_ \ / _` | | | | __|
+| |  | | | (__| | | (_) | | | | (_| | |_| | |_ 
+|_|  |_|_|\___|_|  \___/|_| |_|\__,_|\__,_|\__|
+12:20:53.437 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 6ms. Server Running: http://localhost:8080
+```
+and test our custom endpoint:
+```bash
+curl localhost:8080/hello
+```
+The expected output is:
+```
+Hello from GraalVM Native Image!
+```
+
+### Layered Application
+
+#### Configure The Base Layer
+
+We will create a base layer that contains both `java.base` and the Micronaut framework.
+For this we'll add a second custom profile:
+```xml
+<profile>
+    <id>base-layer</id>
+    <build>
+    <directory>${project.basedir}/base-layer-target</directory>
+        <plugins>
+            <plugin>
+                <groupId>org.graalvm.buildtools</groupId>
+                <artifactId>native-maven-plugin</artifactId>
+                <version>0.10.3</version>
+                <configuration>
+                    <imageName>libmicronautbaselayer</imageName>
+                    <mainClass>.</mainClass>
+                    <buildArgs>
+                        <buildArg>-H:+UnlockExperimentalVMOptions</buildArg>
+                        <buildArg>-H:LayerCreate=base-layer.nil,module=java.base,package=io.micronaut.*,package=io.netty.*,package=jakarta.*,package=com.fasterxml.jackson.*,package=org.slf4j.*,package=reactor.*,package=org.reactivestreams.*</buildArg>
+                        <buildArg>-H:ApplicationLayerOnlySingletons=io.micronaut.core.io.service.ServiceScanner$StaticServiceDefinitions</buildArg>
+                        <buildArg>-H:ApplicationLayerInitializedClasses=io.micronaut.inject.annotation.AnnotationMetadataSupport</buildArg>
+                        <buildArg>-H:ApplicationLayerInitializedClasses=io.micronaut.core.io.service.MicronautMetaServiceLoaderUtils</buildArg>
+                        <buildArg>-H:-UnlockExperimentalVMOptions</buildArg>
+                    </buildArgs>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</profile>
+```
+
+We use `-H:LayerCreate=` to specify what should be included in the base layer: `java.base`, `io.micronaut`, `io.netty` and a few more other packages that a Micronaut application usually depends on.
+For more details consult the [Native Image Layers documentation](https://github.com/oracle/graal/blob/master/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/imagelayer/NativeImageLayers.md).
+
+Additionally we use two options that are specific for layered builds: `-H:ApplicationLayerOnlySingletons=`, which specifies that a singleton object should be installed in the application layer only, and `-H:ApplicationLayerInitializedClasses=`, which registers a class as being initialized in the app layer.
+These are necessary for correctly building the Micronaut framework in a layered set-up. 
+
+Now we can build the base layer:
+```bash
+./mvnw clean install -Dpackaging=native-image -Pbase-layer
+```
+This will create the `base-layer.nil` which is a build time dependency for the application build.
+It will also create the `libmicronautbaselayer.so` shared library which is a run time dependency for the application layer.
+Note also that we use `install` instead of `package` to ensure that the base layer jar is installed in the `.m2` cache as it will be needed by the application build later.
+
+
+### Configure The Application Layer
+
+To configure the app layer we'll add an additional profile:
+```xml
+<profile>
+    <id>app-layer</id>
+    <build>
+        <directory>${project.basedir}/app-layer-target</directory>
+        <plugins>
+            <plugin>
+                <groupId>org.graalvm.buildtools</groupId>
+                <artifactId>native-maven-plugin</artifactId>
+                <version>0.10.3</version>
+                <configuration>
+                    <imageName>layered-app</imageName>
+                    <mainClass>example.micronaut.Application</mainClass>
+                    <buildArgs>
+                        <buildArg>-H:+UnlockExperimentalVMOptions</buildArg>
+                        <buildArg>-H:LayerUse=base-layer-target/base-layer.nil</buildArg>
+                        <buildArg>-H:LinkerRPath=$ORIGIN</buildArg>
+                        <buildArg>-H:-UnlockExperimentalVMOptions</buildArg>
+                    </buildArgs>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</profile>
+```
+
+Now we can build a layered Native Image which depends on the base layer that we created earlier:
+```bash
+./mvnw clean package -Dpackaging=native-image -Papp-layer
+```
+
+This will generate the layered executable file in `./app-layer-target/layered-app` and will copy `libmicronautbaselayer.so` next to it.
+
+Then we can execute the layered application:
+```bash
+./app-layer-target/layered-app
+ __  __ _                                  _   
+|  \/  (_) ___ _ __ ___  _ __   __ _ _   _| |_ 
+| |\/| | |/ __| '__/ _ \| '_ \ / _` | | | | __|
+| |  | | | (__| | | (_) | | | | (_| | |_| | |_ 
+|_|  |_|_|\___|_|  \___/|_| |_|\__,_|\__,_|\__|
+12:24:21.341 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 6ms. Server Running: http://localhost:8080
+```
+and test it with:
+```
+curl localhost:8080/hello
+```
+The expected output is:
+```
+Hello from GraalVM Native Image!
+```

native-image/microservices/micronaut-hello-rest-maven-layered/aot-jar.properties

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+# AOT configuration properties for jar packaging
+# Please review carefully the optimizations enabled below
+# Check https://micronaut-projects.github.io/micronaut-aot/latest/guide/ for more details
+
+# Caches environment property values: environment properties will be deemed immutable after application startup.
+cached.environment.enabled=true
+
+# Precomputes Micronaut configuration property keys from the current environment variables
+precompute.environment.properties.enabled=true
+
+# Replaces logback.xml with a pure Java configuration
+logback.xml.to.java.enabled=true
+
+# Converts YAML configuration files to Java configuration
+yaml.to.java.config.enabled=true
+
+# Scans for service types ahead-of-time, avoiding classpath scanning at startup
+serviceloading.jit.enabled=true
+
+# Scans reactive types at build time instead of runtime
+scan.reactive.types.enabled=true
+
+# Deduces the environment at build time instead of runtime
+deduce.environment.enabled=true
+
+# Checks for the existence of some types at build time instead of runtime
+known.missing.types.enabled=true
+
+# Precomputes property sources at build time
+sealed.property.source.enabled=true
+
+# The list of service types to be scanned (comma separated)
+service.types=io.micronaut.context.env.PropertySourceLoader,io.micronaut.inject.BeanConfiguration,io.micronaut.inject.BeanDefinitionReference,io.micronaut.http.HttpRequestFactory,io.micronaut.http.HttpResponseFactory,io.micronaut.core.beans.BeanIntrospectionReference,io.micronaut.core.convert.TypeConverterRegistrar,io.micronaut.context.env.PropertyExpressionResolver
+
+# A list of types that the AOT analyzer needs to check for existence (comma separated)
+known.missing.types.list=io.reactivex.Observable,reactor.core.publisher.Flux,kotlinx.coroutines.flow.Flow,io.reactivex.rxjava3.core.Flowable,io.reactivex.rxjava3.core.Observable,io.reactivex.Single,reactor.core.publisher.Mono,io.reactivex.Maybe,io.reactivex.rxjava3.core.Single,io.reactivex.rxjava3.core.Maybe,io.reactivex.Completable,io.reactivex.rxjava3.core.Completable,io.methvin.watchservice.MacOSXListeningWatchService,io.micronaut.core.async.publisher.CompletableFuturePublisher,io.micronaut.core.async.publisher.Publishers.JustPublisher,io.micronaut.core.async.subscriber.Completable
+

native-image/microservices/micronaut-hello-rest-maven-layered/aot-native-image.properties

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+# AOT configuration properties for native-image packaging
+# Please review carefully the optimizations enabled below
+# Check https://micronaut-projects.github.io/micronaut-aot/latest/guide/ for more details
+
+# Caches environment property values: environment properties will be deemed immutable after application startup.
+cached.environment.enabled=true
+
+# Precomputes Micronaut configuration property keys from the current environment variables
+precompute.environment.properties.enabled=true
+
+# Replaces logback.xml with a pure Java configuration
+logback.xml.to.java.enabled=true
+
+# Converts YAML configuration files to Java configuration
+yaml.to.java.config.enabled=false
+
+# Generates GraalVM configuration files required to load the AOT optimizations
+graalvm.config.enabled=true
+
+# Scans for service types ahead-of-time, avoiding classpath scanning at startup
+serviceloading.native.enabled=false
+
+# Scans reactive types at build time instead of runtime
+scan.reactive.types.enabled=true
+
+# Deduces the environment at build time instead of runtime
+deduce.environment.enabled=true
+
+# Checks for the existence of some types at build time instead of runtime
+known.missing.types.enabled=true
+
+# Precomputes property sources at build time
+sealed.property.source.enabled=true
+
+# The list of service types to be scanned (comma separated)
+service.types=io.micronaut.context.env.PropertySourceLoader,io.micronaut.inject.BeanConfiguration,io.micronaut.inject.BeanDefinitionReference,io.micronaut.http.HttpRequestFactory,io.micronaut.http.HttpResponseFactory,io.micronaut.core.beans.BeanIntrospectionReference,io.micronaut.core.convert.TypeConverterRegistrar,io.micronaut.context.env.PropertyExpressionResolver
+
+# A list of types that the AOT analyzer needs to check for existence (comma separated)
+known.missing.types.list=io.reactivex.Observable,reactor.core.publisher.Flux,kotlinx.coroutines.flow.Flow,io.reactivex.rxjava3.core.Flowable,io.reactivex.rxjava3.core.Observable,io.reactivex.Single,reactor.core.publisher.Mono,io.reactivex.Maybe,io.reactivex.rxjava3.core.Single,io.reactivex.rxjava3.core.Maybe,io.reactivex.Completable,io.reactivex.rxjava3.core.Completable,io.methvin.watchservice.MacOSXListeningWatchService,io.micronaut.core.async.publisher.CompletableFuturePublisher,io.micronaut.core.async.publisher.Publishers.JustPublisher,io.micronaut.core.async.subscriber.Completable
+

native-image/microservices/micronaut-hello-rest-maven-layered/micronaut-cli.yml

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+applicationType: default
+defaultPackage: example.micronaut
+testFramework: junit
+sourceLanguage: java
+buildTool: maven
+features: [app-name, graalvm, http-client-test, java, java-application, junit, logback, maven, maven-enforcer-plugin, micronaut-aot, micronaut-http-validation, netty-server, properties, readme, serialization-jackson, shade, static-resources]