feature: ResourceID from first owner reference (#841)

Author: csviri

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/event/source/informer/Mappers.java

@@ -29,6 +29,18 @@ public static <T extends HasMetadata> PrimaryResourcesRetriever<T> fromLabel(
     return fromMetadata(nameKey, namespaceKey, true);
   }
 
+  public static <T extends HasMetadata> PrimaryResourcesRetriever<T> fromOwnerReference() {
+    return resource -> {
+      var ownerReferences = resource.getMetadata().getOwnerReferences();
+      if (!ownerReferences.isEmpty()) {
+        return Set.of(new ResourceID(ownerReferences.get(0).getName(),
+            resource.getMetadata().getNamespace()));
+      } else {
+        return Collections.emptySet();
+      }
+    };
+  }
+
   private static <T extends HasMetadata> PrimaryResourcesRetriever<T> fromMetadata(
       String nameKey, String namespaceKey, boolean isLabel) {
     return resource -> {

sample-operators/tomcat-operator/src/main/java/io/javaoperatorsdk/operator/sample/TomcatReconciler.java

@@ -4,7 +4,6 @@
 import java.io.InputStream;
 import java.util.List;
 import java.util.Objects;
-import java.util.Set;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -22,12 +21,11 @@
 import io.javaoperatorsdk.operator.api.reconciler.EventSourceInitializer;
 import io.javaoperatorsdk.operator.api.reconciler.Reconciler;
 import io.javaoperatorsdk.operator.api.reconciler.UpdateControl;
-import io.javaoperatorsdk.operator.processing.event.ResourceID;
 import io.javaoperatorsdk.operator.processing.event.source.EventSource;
 import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
+import io.javaoperatorsdk.operator.processing.event.source.informer.Mappers;
 
 import static io.javaoperatorsdk.operator.api.reconciler.Constants.NO_FINALIZER;
-import static java.util.Collections.EMPTY_SET;
 
 /**
  * Runs a specified number of Tomcat app server Pods. It uses a Deployment to create the Pods. Also
@@ -52,15 +50,7 @@ public List<EventSource> prepareEventSources(EventSourceContext<Tomcat> context)
             .runnableInformer(0);
 
     return List.of(new InformerEventSource<>(
-        deploymentInformer, d -> {
-          var ownerReferences = d.getMetadata().getOwnerReferences();
-          if (!ownerReferences.isEmpty()) {
-            return Set.of(new ResourceID(ownerReferences.get(0).getName(),
-                d.getMetadata().getNamespace()));
-          } else {
-            return EMPTY_SET;
-          }
-        }));
+        deploymentInformer, Mappers.fromOwnerReference()));
   }
 
   @Override