Fix the issue of ONOS-3423

Change-Id: I60c3105149f6ef46e2effb7de6d8f40152027ec7

@@ -121,10 +121,10 @@ public abstract class ResourcePath {
     public List<Object> components() {
         LinkedList<Object> components = new LinkedList<>();
 
-        Optional<Discrete> parentPath = Optional.ofNullable(parent);
-        while (parentPath.isPresent()) {
-            components.addFirst(last);
-            parentPath = parent.parent();
+        ResourcePath current = this;
+        while (current.parent().isPresent()) {
+            components.addFirst(current.last);
+            current = current.parent;
         }
 
         return components;

@@ -26,6 +26,7 @@ import org.onosproject.net.PortNumber;
 
 import java.util.Optional;
 
+import static org.hamcrest.Matchers.contains;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertThat;
 
@@ -63,6 +64,13 @@ public class ResourcePathTest {
     }
 
     @Test
+    public void testComponents() {
+        ResourcePath port = ResourcePath.discrete(D1, P1);
+
+        assertThat(port.components(), contains(D1, P1));
+    }
+
+    @Test
     public void testThereIsParent() {
         ResourcePath path = ResourcePath.discrete(LinkKey.linkKey(CP1_1, CP2_1), VLAN1);
         ResourcePath parent = ResourcePath.discrete(LinkKey.linkKey(CP1_1, CP2_1));

@@ -59,17 +59,15 @@ public final class ResourceRegistrar {
 
     @Activate
     public void activate() {
-        // FIXME there is a loop causing high resource utilization on device registration
-//        deviceListener = new ResourceDeviceListener(adminService, executor);
-//        deviceService.addListener(deviceListener);
-//        linkListener = new ResourceLinkListener(adminService, driverService, executor);
-//        linkService.addListener(linkListener);
+        deviceListener = new ResourceDeviceListener(adminService, executor);
+        deviceService.addListener(deviceListener);
+        linkListener = new ResourceLinkListener(adminService, driverService, executor);
+        linkService.addListener(linkListener);
     }
 
     @Deactivate
     public void deactivate() {
-        // FIXME there is a loop causing high resource utilization on device registration
-//        deviceService.removeListener(deviceListener);
-//        linkService.removeListener(linkListener);
+        deviceService.removeListener(deviceListener);
+        linkService.removeListener(linkListener);
     }
 }