GossipDeviceStore: Notifying applications of latest topology events received from peers

 package org.onlab.onos.store;
 
+import java.util.List;
+
 import org.onlab.onos.event.Event;
 
 import static com.google.common.base.Preconditions.checkState;
@@ -41,4 +43,15 @@ public class AbstractStore<E extends Event, D extends StoreDelegate<E>>
             delegate.notify(event);
         }
     }
+
+    /**
+     * Notifies the delegate with the specified list of events.
+     *
+     * @param events list of events to delegate
+     */
+    protected void notifyDelegate(List<E> events) {
+        for (E event: events) {
+            notifyDelegate(event);
+        }
+    }
 }

@@ -870,6 +870,12 @@ public class GossipDeviceStore
         clusterCommunicator.broadcast(message);
     }
 
+    private void notifyDelegateIfNotNull(DeviceEvent event) {
+        if (event != null) {
+            notifyDelegate(event);
+        }
+    }
+
     private class InternalDeviceEventListener implements ClusterMessageHandler {
         @Override
         public void handle(ClusterMessage message) {
@@ -881,7 +887,7 @@ public class GossipDeviceStore
             DeviceId deviceId = event.deviceId();
             Timestamped<DeviceDescription> deviceDescription = event.deviceDescription();
 
-            createOrUpdateDeviceInternal(providerId, deviceId, deviceDescription);
+            notifyDelegateIfNotNull(createOrUpdateDeviceInternal(providerId, deviceId, deviceDescription));
         }
     }
 
@@ -895,7 +901,7 @@ public class GossipDeviceStore
             DeviceId deviceId = event.deviceId();
             Timestamp timestamp = event.timestamp();
 
-            markOfflineInternal(deviceId, timestamp);
+            notifyDelegateIfNotNull(markOfflineInternal(deviceId, timestamp));
         }
     }
 
@@ -909,7 +915,7 @@ public class GossipDeviceStore
             DeviceId deviceId = event.deviceId();
             Timestamp timestamp = event.timestamp();
 
-            removeDeviceInternal(deviceId, timestamp);
+            notifyDelegateIfNotNull(removeDeviceInternal(deviceId, timestamp));
         }
     }
 
@@ -924,7 +930,7 @@ public class GossipDeviceStore
             DeviceId deviceId = event.deviceId();
             Timestamped<List<PortDescription>> portDescriptions = event.portDescriptions();
 
-            updatePortsInternal(providerId, deviceId, portDescriptions);
+            notifyDelegate(updatePortsInternal(providerId, deviceId, portDescriptions));
         }
     }
 
@@ -939,7 +945,7 @@ public class GossipDeviceStore
             DeviceId deviceId = event.deviceId();
             Timestamped<PortDescription> portDescription = event.portDescription();
 
-            updatePortStatusInternal(providerId, deviceId, portDescription);
+            notifyDelegateIfNotNull(updatePortStatusInternal(providerId, deviceId, portDescription));
         }
     }
 }