[ONOS-3894, 4071] YANG Advanced Construct Union & Grouping

Change-Id: I0f828adb5884c2d7b6e4120f9843c416608ae5e7
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
index 5d6a744..b000242 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
@@ -22,6 +22,8 @@
 import org.onosproject.yangutils.datamodel.YangLeafList;
 import org.onosproject.yangutils.datamodel.YangType;
 import org.onosproject.yangutils.datamodel.YangTypeDef;
+import org.onosproject.yangutils.datamodel.YangUnion;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
@@ -116,6 +118,17 @@
                 YangLeafList leafList = (YangLeafList) tmpData;
                 leafList.setDataType((YangType<?>) type);
                 break;
+            case UNION_DATA:
+                YangUnion unionNode = (YangUnion) tmpData;
+                try {
+                    unionNode.addToTypeList((YangType<?>) type);
+                } catch (DataModelException e) {
+                    ParserException parserException = new ParserException(e.getMessage());
+                    parserException.setLine(ctx.getStart().getLine());
+                    parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+                    throw parserException;
+                }
+                break;
             case TYPEDEF_DATA:
 
                 /* Prepare the base type info and set in derived type */