Using a Feature to specify MySampleFileSystemProvider is initialized at build time

child-project-2/pom.xml

@@ -33,6 +33,12 @@
       <artifactId>javax.inject</artifactId>
       <version>1</version>
     </dependency>
+    <dependency>
+      <groupId>org.graalvm.nativeimage</groupId>
+      <artifactId>svm</artifactId>
+      <version>22.0.0.2</version>
+      <scope>provided</scope>
+    </dependency>
   </dependencies>
 
 </project>

child-project-2/src/main/java/com/example/FooClass.java

@@ -0,0 +1,13 @@
+package com.example;
+
+import java.util.Date;
+
+public class FooClass {
+
+  static {
+    System.out.println("***** FooClass is being initialized *****");
+    d = new Date();
+  }
+
+  static final Date d;
+}

child-project-2/src/main/java/com/example/features/MySampleFileSystemProviderFeature.java

@@ -0,0 +1,24 @@
+package com.example.features;
+
+import com.oracle.svm.core.annotate.AutomaticFeature;
+import org.graalvm.nativeimage.hosted.Feature;
+import org.graalvm.nativeimage.hosted.RuntimeClassInitialization;
+
+@AutomaticFeature
+final class MySampleFileSystemProviderFeature implements Feature {
+  private static final String clazz = "com.example.MySampleFileSystemProvider";
+
+  @Override
+  public void beforeAnalysis(BeforeAnalysisAccess access) {
+    // For MySampleFileSystemProvider, this feature does not tell native-image to initialize the
+    // class at build time. Rather, this feature tells the analysis phase ("[2/7] Performing
+    // analysis... ") not to complain when the class is already initialized. It's because
+    // MySampleFileSystemProvider is already initialized before the initializing phase ("[1/7]
+    // Initializing... "), in which native-image reads user-provided feature(s).
+    RuntimeClassInitialization.initializeAtBuildTime(clazz);
+
+    // On the other hand, this tells the native-image to initialize com.example.FooClass at build
+    // time, because when native-image reads this feature, FooClass has not been initialized.
+    RuntimeClassInitialization.initializeAtBuildTime("com.example.FooClass");
+  }
+}

child-project-2/src/main/resources/META-INF/native-image/native-image.properties

@@ -1,2 +1 @@
-Args = --initialize-at-run-time=com.example \
---initialize-at-build-time=com.example.MySampleFileSystemProvider
+Args = --enable-url-protocols=http -H:+PrintClassInitialization

child-project-2/src/test/java/com/example/SimpleTest.java

@@ -4,6 +4,9 @@
 
 import com.google.cloud.storage.StorageOptions;
 import com.google.cloud.storage.testing.RemoteStorageHelper;
+import com.google.common.truth.Correspondence;
+import java.nio.file.spi.FileSystemProvider;
+import java.util.ServiceLoader;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -32,4 +35,29 @@ public void testMessage(){
     MySampleFileSystem.forBucket("bucket",config, gcsHelper.getOptions());
     assertThat("hello1").isEqualTo("hello1");
   }
+
+  @Test
+  public void testServiceLoader() {
+    ServiceLoader<FileSystemProvider> fileSystemProviders =
+        ServiceLoader.load(FileSystemProvider.class);
+    for (FileSystemProvider fileSystemProvider : fileSystemProviders) {
+      System.out.println("FileSystemProvider: " + fileSystemProvider.getClass().getName());
+    }
+    assertThat(fileSystemProviders)
+        .comparingElementsUsing(
+            Correspondence.transforming(
+                provider -> provider.getClass().getName(), "with its name == "))
+        .contains("com.example.MySampleFileSystemProvider");
+    assertThat(fileSystemProviders)
+        .comparingElementsUsing(
+            Correspondence.transforming(
+                (FileSystemProvider provider) -> provider.getScheme(), "with its scheme equals "))
+        .contains("gs");
+  }
+
+  @Test
+  public void testFoo() {
+    assertThat(FooClass.class.getName()).isEqualTo("com.example.FooClass");
+    System.out.println(FooClass.d);
+  }
 }