Define ID representation for Intent, IFlow and MatchAction

- Defines BatchOperationTargetId abstract class.
- The above class is the base class of IntentId, FlowId, and MatchActionId.
 -- Intent objects use IntentId class for its ID.
 -- IFlow objects use FlowId class for its ID.
 -- MatchAction objects use MatchActionId class for its ID.
- BatchOperation classes requires the BatchOperationTargetId as the target object's ID.
- This work is a part of ONOS-1758.

Change-Id: I71bb4e6acd3836d1ced3beb6fb331bca451abdc3
diff --git a/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java b/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java
index 82a9b50..473b7e8 100644
--- a/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java
+++ b/src/main/java/net/onrc/onos/api/flowmanager/SingleDstTreeFlow.java
@@ -18,7 +18,7 @@
  * address modifications or other the label-switching-like schemes.
  */
 public class SingleDstTreeFlow implements IFlow {
-    protected String id;
+    protected final FlowId id;
     protected PacketMatch match;
     protected Set<SwitchPort> ingressPorts;
     protected Tree tree;
@@ -35,7 +35,7 @@
      */
     public SingleDstTreeFlow(String id, PacketMatch match,
             Collection<SwitchPort> ingressPorts, Tree tree, OutputAction outputAction) {
-        this.id = id;
+        this.id = new FlowId(id);
         this.match = match;
         this.ingressPorts = new HashSet<SwitchPort>(ingressPorts);
         this.tree = tree;
@@ -46,7 +46,7 @@
     }
 
     @Override
-    public String getId() {
+    public FlowId getId() {
         return id;
     }