[ONOS-5647] (vnet SBI) Skeleton for VirtualGroupProvider object.

Changes.
1. Default Virtual Group Provider is added

Change-Id: I08aaa1c94d514520eea9d627449d4638b5585715
diff --git a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/provider/DefaultVirtualGroupProvider.java b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/provider/DefaultVirtualGroupProvider.java
new file mode 100644
index 0000000..9383475
--- /dev/null
+++ b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/provider/DefaultVirtualGroupProvider.java
@@ -0,0 +1,130 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.incubator.net.virtual.impl.provider;
+
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Modified;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onosproject.incubator.net.virtual.NetworkId;
+import org.onosproject.incubator.net.virtual.provider.AbstractVirtualProvider;
+import org.onosproject.incubator.net.virtual.provider.VirtualGroupProvider;
+import org.onosproject.incubator.net.virtual.provider.VirtualProviderRegistryService;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.group.GroupEvent;
+import org.onosproject.net.group.GroupListener;
+import org.onosproject.net.group.GroupOperation;
+import org.onosproject.net.group.GroupOperations;
+import org.onosproject.net.group.GroupService;
+import org.onosproject.net.provider.ProviderId;
+import org.osgi.service.component.ComponentContext;
+import org.slf4j.Logger;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Provider to handle Group for virtual network.
+ */
+@Component(immediate = true)
+@Service
+public class DefaultVirtualGroupProvider extends AbstractVirtualProvider
+        implements VirtualGroupProvider {
+
+    private final Logger log = getLogger(getClass());
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected VirtualProviderRegistryService providerRegistryService;
+
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected GroupService groupService;
+
+    private InternalGroupEventListener internalGroupEventListener;
+
+    /**
+     * Creates a virtual provider with the supplied identifier.
+     */
+    public DefaultVirtualGroupProvider() {
+        super(new ProviderId("vnet-group", "org.onosproject.virtual.of-group"));
+    }
+
+    @Activate
+    public void activate() {
+        providerRegistryService.registerProvider(this);
+
+        internalGroupEventListener = new InternalGroupEventListener();
+        groupService.addListener(internalGroupEventListener);
+
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        groupService.removeListener(internalGroupEventListener);
+        providerRegistryService.unregisterProvider(this);
+    }
+
+    @Modified
+    protected void modified(ComponentContext context) {
+    }
+
+    @Override
+    public void performGroupOperation(NetworkId networkId, DeviceId deviceId, GroupOperations groupOps) {
+        for (GroupOperation groupOperation: groupOps.operations()) {
+            switch (groupOperation.opType()) {
+                case ADD:
+                    //TODO: devirtualize + groupAdd
+                    log.info("Group Add is not supported, yet");
+                    break;
+                case MODIFY:
+                    //TODO: devirtualize + groupMod
+                    log.info("Group Modify is not supported, yet");
+                    break;
+                case DELETE:
+                    //TODO: devirtualize + groupDel
+                    log.info("Group Delete is not supported, yet");
+                    break;
+                default:
+                    log.error("Unsupported Group operation");
+                    return;
+            }
+        }
+    }
+
+    private class InternalGroupEventListener implements GroupListener {
+        @Override
+        public void event(GroupEvent event) {
+            switch (event.type()) {
+                //TODO: virtualize + notify to virtual provider service
+                case GROUP_ADD_REQUESTED:
+                case GROUP_UPDATE_REQUESTED:
+                case GROUP_REMOVE_REQUESTED:
+                case GROUP_ADDED:
+                case GROUP_UPDATED:
+                case GROUP_REMOVED:
+                case GROUP_ADD_FAILED:
+                case GROUP_UPDATE_FAILED:
+                case GROUP_REMOVE_FAILED:
+                case GROUP_BUCKET_FAILOVER:
+                default:
+                    break;
+            }
+        }
+    }
+}