Added getter needed for a usage in onos-app-samples

Change-Id: Idd5b2102d96a6a526bd08eb12de6edc64efcb443
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/domain/DomainVertex.java b/incubator/api/src/main/java/org/onosproject/incubator/net/domain/DomainVertex.java
index 0fdf25a..7d11a76 100644
--- a/incubator/api/src/main/java/org/onosproject/incubator/net/domain/DomainVertex.java
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/domain/DomainVertex.java
@@ -33,6 +33,7 @@
     // A domain vertex is either an intent domain or a device:
     private final IntentDomainId domainId;
     // ----- or -----
+
     private final DeviceId deviceId;
 
     // Serialization constructor
@@ -66,4 +67,22 @@
                     .toString();
         }
     }
+
+    /**
+     * Returns the device ID of this vertex if it is a device, returns null if it is a domain.
+     *
+     * @return the device ID of this vertex if applicable, else null
+     */
+    public DeviceId deviceId() {
+        return deviceId;
+    }
+
+    /**
+     * Returns the domain ID of this vertex if it is a domain, returns null if it is a device.
+     *
+     * @return the domain ID of this vertex if applicable, else null
+     */
+    public IntentDomainId domainId() {
+        return domainId;
+    }
 }