[ONOS-7141][ONOS-7142] Add GnmiClient and GnmiController

Change-Id: I6347da378d9e4b59a38e2efacc27599b96dc1515
diff --git a/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java b/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java
new file mode 100644
index 0000000..7ddc3f0
--- /dev/null
+++ b/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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 protocols.gnmi.ctl.java.org.onosproject.gnmi.ctl;
+
+import io.grpc.ManagedChannel;
+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.Service;
+import org.onosproject.gnmi.api.GnmiEvent;
+import org.onosproject.gnmi.api.GnmiEventListener;
+import org.onosproject.grpc.ctl.AbstractGrpcClientController;
+import org.onosproject.gnmi.api.GnmiClient;
+import org.onosproject.gnmi.api.GnmiClientKey;
+import org.onosproject.gnmi.api.GnmiController;
+import org.slf4j.Logger;
+
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Implementation of gNMI controller.
+ */
+@Component(immediate = true)
+@Service
+public class GnmiControllerImpl
+        extends AbstractGrpcClientController<GnmiClientKey, GnmiClient, GnmiEvent, GnmiEventListener>
+        implements GnmiController {
+    private final Logger log = getLogger(getClass());
+
+    @Activate
+    public void activate() {
+        super.activate();
+        log.info("Started");
+    }
+
+    @Deactivate
+    public void deactivate() {
+        super.deactivate();
+        log.info("Stopped");
+    }
+
+    @Override
+    protected GnmiClient createClientInstance(GnmiClientKey clientKey, ManagedChannel channel) {
+        return new GnmiClientImpl(clientKey, channel);
+    }
+}