feat: add defaultJvmArgs for javaApplication and switch to java 21 (#37)

* feat: add default jvm args for java application plugin

* also modify default to 21

* nit

* update

Author: Kishan Sairam Adapa

hypertrace-gradle-docker-java-application-plugin/README.md

@@ -15,7 +15,7 @@ An application can define multiple variants which allow specifying different bas
 
 - `baseImage`
     - String
-    - Defaults to `hypertrace/java:11`
+    - Defaults to `hypertrace/java:21`
 - `maintainer`
     - String
     - Defaults to `Hypertrace 'https://www.hypertrace.org/'`

hypertrace-gradle-docker-java-application-plugin/src/main/java/org/hypertrace/gradle/docker/HypertraceDockerJavaApplication.java

@@ -1,6 +1,7 @@
 package org.hypertrace.gradle.docker;
 
 import java.util.Collections;
+import java.util.List;
 import javax.inject.Inject;
 import org.gradle.api.artifacts.ResolvedArtifact;
 import org.gradle.api.model.ObjectFactory;
@@ -29,7 +30,7 @@ public class HypertraceDockerJavaApplication {
   public HypertraceDockerJavaApplication(
       ObjectFactory objectFactory, String projectName) {
     this.baseImage = objectFactory.property(String.class)
-                                  .convention("hypertrace/java:11");
+                                  .convention("hypertrace/java:21");
     this.maintainer = objectFactory.property(String.class)
                                    .convention("Hypertrace 'https://www.hypertrace.org/'");
     this.serviceName = objectFactory.property(String.class)

hypertrace-gradle-docker-java-application-plugin/src/main/java/org/hypertrace/gradle/docker/HypertraceDockerJavaApplicationPlugin.java

@@ -56,6 +56,7 @@ public void apply(Project target) {
     this.createDockerfileTask(target, this.getHypertraceDockerApplicationExtension(target));
     this.createDockerStartScriptTask(target);
     this.createContextSyncTask(target);
+    this.updateDefaultJvmArgs(target);
     this.updateDefaultPublication(target);
   }
 
@@ -65,6 +66,14 @@ private void addApplicationExtension(Project project) {
         .create(EXTENSION_NAME, HypertraceDockerJavaApplication.class, project.getName());
   }
 
+  private void updateDefaultJvmArgs(Project project) {
+    // by default allow reflective access for monitoring executor service
+    // https://github.com/micrometer-metrics/micrometer/issues/2317#issuecomment-952700482
+    project.getExtensions()
+      .getByType(JavaApplication.class)
+      .setApplicationDefaultJvmArgs(List.of("--add-opens", "java.base/java.util.concurrent=ALL-UNNAMED"));
+  }
+
   private void updateDefaultPublication(Project project) {
     this.getHypertraceDockerExtension(project)
         .defaultImage(