ONOS-2186 - GUI Topo Overlay - (WIP)
- Moved TopoJson to core ui API, so it is accessible to external apps
- Added highlightsMessage() to TopoJson
- Pulled sendMessage() up to UiMessageHandler

Change-Id: Iacab5b69e3b2a6db98be8391274695247ba5526d
diff --git a/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java b/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java
index e27f5d9..9b9a406 100644
--- a/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java
+++ b/core/api/src/main/java/org/onosproject/ui/UiMessageHandler.java
@@ -190,4 +190,18 @@
     protected ArrayNode arrayNode() {
         return mapper.createArrayNode();
     }
+
+    /**
+     * Sends the specified data to the client.
+     * It is expected that the data is in the prescribed JSON format for
+     * events to the client.
+     *
+     * @param data data to be sent
+     */
+    protected synchronized void sendMessage(ObjectNode data) {
+        UiConnection connection = connection();
+        if (connection != null) {
+            connection.sendMessage(data);
+        }
+    }
 }