[ONOS-2159]Add to query devices by type api in DeviceService and

DeviceStore interfaces

Change-Id: Ifa7e94e08eb150fb4d71248a50a390832d1549df

@@ -44,6 +44,15 @@ public interface DeviceService {
     Iterable<Device> getDevices();
 
     /**
+     * Returns a collection of the currently known infrastructure
+     * devices by device type.
+     *
+     * @param type device type
+     * @return collection of devices
+     */
+    Iterable<Device> getDevices(Device.Type type);
+
+    /**
      * Returns an iterable collection of all devices
      * currently available to the system.
      *
@@ -52,6 +61,14 @@ public interface DeviceService {
     Iterable<Device> getAvailableDevices();
 
     /**
+     * Returns an iterable collection of all devices currently available to the system by device type.
+     *
+     * @param type device type
+     * @return device collection
+     */
+    Iterable<Device> getAvailableDevices(Device.Type type);
+
+    /**
      * Returns the device with the specified identifier.
      *
      * @param deviceId device identifier

@@ -19,6 +19,7 @@ import com.google.common.base.Predicate;
 import com.google.common.collect.FluentIterable;
 
 import org.onosproject.net.Device;
+import org.onosproject.net.Device.Type;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.MastershipRole;
 import org.onosproject.net.Port;
@@ -91,4 +92,14 @@ public class DeviceServiceAdapter implements DeviceService {
     public void removeListener(DeviceListener listener) {
     }
 
+    @Override
+    public Iterable<Device> getDevices(Type type) {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public Iterable<Device> getAvailableDevices(Type type) {
+        return Collections.emptyList();
+    }
+
 }