refactor TopoDevicesResource class to use GraphDBOperation class.
diff --git a/src/main/java/net/floodlightcontroller/devicemanager/web/TopoDevicesResource.java b/src/main/java/net/floodlightcontroller/devicemanager/web/TopoDevicesResource.java
index db7059f..1660336 100644
--- a/src/main/java/net/floodlightcontroller/devicemanager/web/TopoDevicesResource.java
+++ b/src/main/java/net/floodlightcontroller/devicemanager/web/TopoDevicesResource.java
@@ -4,6 +4,7 @@
 
 import net.floodlightcontroller.core.INetMapTopologyObjects.IDeviceObject;
 import net.onrc.onos.util.GraphDBConnection;
+import net.onrc.onos.util.GraphDBOperation;
 
 import org.restlet.resource.Get;
 import org.restlet.resource.ServerResource;
@@ -14,8 +15,9 @@
 	public Iterator<IDeviceObject> retrieve() {
 		
 		GraphDBConnection conn = GraphDBConnection.getInstance("");
+		GraphDBOperation op = new GraphDBOperation(conn);
 		
-		return conn.utils().getDevices(conn).iterator();
+		return op.getDevices().iterator();
 		
 	}