[ONOS-3880, 3881] Yang Listener for Module and Sub-Module

Change-Id: Iee75c3e04af9b66ebc38acb3396aa4c54af5a268
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BaseFileListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BaseFileListener.java
index 355c268..f53a767 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BaseFileListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BaseFileListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -48,7 +57,11 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processYangFileEntry(TreeWalkListener listener, GeneratedYangParser.YangfileContext ctx) {
-        // TODO method implementation
+
+        // Check if stack is empty.
+        ListenerValidation.checkStackIsEmpty(listener, ListenerErrorType.INVALID_HOLDER,
+                                             ParsableDataType.YANGBASE_DATA, "", ListenerErrorLocation.ENTRY);
+
     }
 
     /**
@@ -59,6 +72,25 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processYangFileExit(TreeWalkListener listener, GeneratedYangParser.YangfileContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.YANGBASE_DATA, "", ListenerErrorLocation.EXIT);
+
+        // Data Model tree root node is set.
+        if (listener.getParsedDataStack().peek() instanceof YangModule
+                | listener.getParsedDataStack().peek() instanceof YangSubModule) {
+            listener.setRootNode((YangNode) listener.getParsedDataStack().pop());
+        } else {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.INVALID_CHILD,
+                                                                             ParsableDataType.YANGBASE_DATA, "",
+                                                                             ListenerErrorLocation.EXIT));
+        }
+
+        // Check if stack is empty.
+        ListenerValidation.checkStackIsEmpty(listener, ListenerErrorType.INVALID_HOLDER,
+                                             ParsableDataType.YANGBASE_DATA, "", ListenerErrorLocation.EXIT);
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java
index efb997e..c8266dc 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangBelongsTo;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -64,7 +73,18 @@
      */
     public static void processBelongsToEntry(TreeWalkListener listener,
                                              GeneratedYangParser.BelongstoStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.BELONGS_TO_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.ENTRY);
+
+        YangBelongsTo belongstoNode = new YangBelongsTo();
+        belongstoNode.setBelongsToModuleName(String.valueOf(ctx.IDENTIFIER().getText()));
+
+        // Push belongsto into the stack.
+        listener.getParsedDataStack().push(belongstoNode);
     }
 
     /**
@@ -76,6 +96,47 @@
      */
     public static void processBelongsToExit(TreeWalkListener listener,
                                             GeneratedYangParser.BelongstoStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.BELONGS_TO_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.EXIT);
+
+        Parsable tmpBelongstoNode = listener.getParsedDataStack().peek();
+        if (tmpBelongstoNode instanceof YangBelongsTo) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be empty.
+            ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                    ParsableDataType.BELONGS_TO_DATA,
+                                                    String.valueOf(ctx.IDENTIFIER().getText()),
+                                                    ListenerErrorLocation.EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getParsableDataType()) {
+            case SUB_MODULE_DATA: {
+                YangSubModule subModule = (YangSubModule) tmpNode;
+                subModule.setBelongsTo((YangBelongsTo) tmpBelongstoNode);
+                break;
+            }
+            default:
+                throw new ParserException(
+                                          ListenerErrorMessageConstruction
+                                                  .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                                 ParsableDataType.BELONGS_TO_DATA,
+                                                                                 String.valueOf(ctx.IDENTIFIER()
+                                                                                         .getText()),
+                                                                                 ListenerErrorLocation.EXIT));
+            }
+        } else {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.MISSING_CURRENT_HOLDER,
+                                                                             ParsableDataType.BELONGS_TO_DATA,
+                                                                             String.valueOf(ctx.IDENTIFIER()
+                                                                                     .getText()),
+                                                                             ListenerErrorLocation.EXIT));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContactListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContactListener.java
index 3ad513c..48174b5 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContactListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContactListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -28,8 +37,7 @@
  *                       [contact-stmt stmtsep]
  *                       [description-stmt stmtsep]
  *                       [reference-stmt stmtsep]
- * organization-stmt   = organization-keyword sep string
- *                            optsep stmtend
+ * contact-stmt        = contact-keyword sep string optsep stmtend
  *
  * ANTLR grammar rule
  * meta_stmts : organization_stmt? contact_stmt? description_stmt? reference_stmt?
@@ -57,7 +65,7 @@
  *            | description_stmt? organization_stmt? contact_stmt? reference_stmt?
  *            | description_stmt? organization_stmt? reference_stmt? contact_stmt?
  *            ;
- * organization_stmt : ORGANIZATION_KEYWORD string STMTEND;
+ * contact_stmt : CONTACT_KEYWORD string STMTEND;
  */
 
 /**
@@ -81,6 +89,32 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processContactEntry(TreeWalkListener listener, GeneratedYangParser.ContactStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.CONTACT_DATA,
+                                                String.valueOf(ctx.string().getText()), ListenerErrorLocation.ENTRY);
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+        case MODULE_DATA: {
+            YangModule module = (YangModule) tmpNode;
+            module.setContact(String.valueOf(ctx.string().getText()));
+            break;
+        }
+        case SUB_MODULE_DATA: {
+            YangSubModule subModule = (YangSubModule) tmpNode;
+            subModule.setContact(String.valueOf(ctx.string().getText()));
+            break;
+        }
+        default:
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                             ParsableDataType.CONTACT_DATA,
+                                                                             String.valueOf(ctx.string().getText()),
+                                                                             ListenerErrorLocation.ENTRY));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
index ef53b3d..4740699 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
@@ -16,8 +16,18 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangImport;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -62,7 +72,18 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processImportEntry(TreeWalkListener listener, GeneratedYangParser.ImportStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.IMPORT_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.ENTRY);
+
+        YangImport importNode = new YangImport();
+        importNode.setModuleName(String.valueOf(ctx.IDENTIFIER().getText()));
+
+        // Push import node to the stack.
+        listener.getParsedDataStack().push(importNode);
     }
 
     /**
@@ -73,6 +94,52 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processImportExit(TreeWalkListener listener, GeneratedYangParser.ImportStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.IMPORT_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.EXIT);
+
+        Parsable tmpImportNode = listener.getParsedDataStack().peek();
+        if (tmpImportNode instanceof YangImport) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                    ParsableDataType.IMPORT_DATA,
+                                                    String.valueOf(ctx.IDENTIFIER().getText()),
+                                                    ListenerErrorLocation.EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getParsableDataType()) {
+            case MODULE_DATA: {
+                YangModule module = (YangModule) tmpNode;
+                module.addImportedInfo((YangImport) tmpImportNode);
+                break;
+            }
+            case SUB_MODULE_DATA: {
+                YangSubModule subModule = (YangSubModule) tmpNode;
+                subModule.addImportedInfo((YangImport) tmpImportNode);
+                break;
+            }
+            default:
+                throw new ParserException(
+                                          ListenerErrorMessageConstruction
+                                                  .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                                 ParsableDataType.IMPORT_DATA,
+                                                                                 String.valueOf(ctx.IDENTIFIER()
+                                                                                         .getText()),
+                                                                                 ListenerErrorLocation.EXIT));
+            }
+        } else {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.MISSING_CURRENT_HOLDER,
+                                                                             ParsableDataType.IMPORT_DATA, String
+                                                                                     .valueOf(ctx.IDENTIFIER()
+                                                                                             .getText()),
+                                                                             ListenerErrorLocation.EXIT));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java
index bc78e7d..c4678b8 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java
@@ -16,8 +16,18 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangInclude;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -37,7 +47,7 @@
  * linkage_stmts : (import_stmt
  *               | include_stmt)*;
  * include_stmt : INCLUDE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE
- *                revision_date_stmt_body? RIGHT_CURLY_BRACE);
+ *                revision_date_stmt? RIGHT_CURLY_BRACE);
  */
 
 /**
@@ -61,7 +71,17 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processIncludeEntry(TreeWalkListener listener, GeneratedYangParser.IncludeStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.INCLUDE_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.ENTRY);
+
+        YangInclude includeNode = new YangInclude();
+        includeNode.setSubModuleName(String.valueOf(ctx.IDENTIFIER().getText()));
+
+        listener.getParsedDataStack().push(includeNode);
     }
 
     /**
@@ -72,6 +92,52 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processIncludeExit(TreeWalkListener listener, GeneratedYangParser.IncludeStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.INCLUDE_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.EXIT);
+
+        Parsable tmpIncludeNode = listener.getParsedDataStack().peek();
+        if (tmpIncludeNode instanceof YangInclude) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                    ParsableDataType.INCLUDE_DATA,
+                                                    String.valueOf(ctx.IDENTIFIER().getText()),
+                                                    ListenerErrorLocation.EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getParsableDataType()) {
+            case MODULE_DATA: {
+                YangModule module = (YangModule) tmpNode;
+                module.addIncludedInfo((YangInclude) tmpIncludeNode);
+                break;
+            }
+            case SUB_MODULE_DATA: {
+                YangSubModule subModule = (YangSubModule) tmpNode;
+                subModule.addIncludedInfo((YangInclude) tmpIncludeNode);
+                break;
+            }
+            default:
+                throw new ParserException(
+                                          ListenerErrorMessageConstruction
+                                                  .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                                 ParsableDataType.INCLUDE_DATA,
+                                                                                 String.valueOf(ctx.IDENTIFIER()
+                                                                                         .getText()),
+                                                                                 ListenerErrorLocation.EXIT));
+            }
+        } else {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.MISSING_CURRENT_HOLDER,
+                                                                             ParsableDataType.INCLUDE_DATA, String
+                                                                                     .valueOf(ctx.IDENTIFIER()
+                                                                                             .getText()),
+                                                                             ListenerErrorLocation.EXIT));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java
index c83b30d..cf6309a 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java
@@ -16,8 +16,15 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -58,7 +65,16 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processModuleEntry(TreeWalkListener listener, GeneratedYangParser.ModuleStatementContext ctx) {
-        // TODO method implementation
+
+        // Check if stack is empty.
+        ListenerValidation
+                .checkStackIsEmpty(listener, ListenerErrorType.INVALID_HOLDER, ParsableDataType.MODULE_DATA,
+                                   String.valueOf(ctx.IDENTIFIER().getText()), ListenerErrorLocation.ENTRY);
+
+        YangModule yangModule = new YangModule();
+        yangModule.setName(ctx.IDENTIFIER().getText());
+
+        listener.getParsedDataStack().push(yangModule);
     }
 
     /**
@@ -69,6 +85,21 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processModuleExit(TreeWalkListener listener, GeneratedYangParser.ModuleStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.MODULE_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.EXIT);
+
+        if (!(listener.getParsedDataStack().peek() instanceof YangModule)) {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.MISSING_CURRENT_HOLDER,
+                                                                             ParsableDataType.MODULE_DATA, String
+                                                                                     .valueOf(ctx.IDENTIFIER()
+                                                                                             .getText()),
+                                                                             ListenerErrorLocation.EXIT));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java
index 6f694e1..8386788 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java
@@ -16,8 +16,19 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNameSpace;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
+
+import java.net.URI;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -63,6 +74,53 @@
      */
     public static void processNamespaceEntry(TreeWalkListener listener,
                                              GeneratedYangParser.NamespaceStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.NAMESPACE_DATA,
+                                                String.valueOf(ctx.string().getText()), ListenerErrorLocation.ENTRY);
+
+        if (!validateUriValue(String.valueOf(ctx.string().getText()))) {
+            ParserException parserException = new ParserException("Invalid namespace URI");
+            parserException.setLine(ctx.string().STRING(0).getSymbol().getLine());
+            parserException.setCharPosition(ctx.string().STRING(0).getSymbol().getCharPositionInLine());
+            throw parserException;
+        }
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+        case MODULE_DATA: {
+            YangModule module = (YangModule) tmpNode;
+            YangNameSpace uri = new YangNameSpace();
+            uri.setUri(String.valueOf(ctx.string().getText()));
+            module.setNameSpace(uri);
+            break;
+        }
+        default:
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                             ParsableDataType.NAMESPACE_DATA,
+                                                                             String.valueOf(ctx.string().getText()),
+                                                                             ListenerErrorLocation.ENTRY));
+        }
     }
-}
+
+    /**
+     * Validate input URI.
+     *
+     * @param uri input namespace URI
+     * @return validation result
+     */
+    private static boolean validateUriValue(String uri) {
+        uri = uri.replace("\"", "");
+        final URI tmpUri;
+        try {
+            tmpUri = URI.create(uri);
+        } catch (Exception e1) {
+            return false;
+        }
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/OrganizationListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/OrganizationListener.java
index e81f15f..edae08e 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/OrganizationListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/OrganizationListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -28,7 +37,8 @@
  *                       [contact-stmt stmtsep]
  *                       [description-stmt stmtsep]
  *                       [reference-stmt stmtsep]
- * contact-stmt        = contact-keyword sep string optsep stmtend
+ * organization-stmt   = organization-keyword sep string
+ *                            optsep stmtend
  *
  * ANTLR grammar rule
  * meta_stmts : organization_stmt? contact_stmt? description_stmt? reference_stmt?
@@ -56,7 +66,7 @@
  *            | description_stmt? organization_stmt? contact_stmt? reference_stmt?
  *            | description_stmt? organization_stmt? reference_stmt? contact_stmt?
  *            ;
- * contact_stmt : CONTACT_KEYWORD string STMTEND;
+ * organization_stmt : ORGANIZATION_KEYWORD string STMTEND;
  */
 
 /**
@@ -81,6 +91,32 @@
      */
     public static void processOrganizationEntry(TreeWalkListener listener,
                                                 GeneratedYangParser.OrganizationStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.ORGANIZATION_DATA,
+                                                String.valueOf(ctx.string().getText()), ListenerErrorLocation.ENTRY);
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+        case MODULE_DATA: {
+            YangModule module = (YangModule) tmpNode;
+            module.setOrganization(String.valueOf(ctx.string().getText()));
+            break;
+        }
+        case SUB_MODULE_DATA: {
+            YangSubModule subModule = (YangSubModule) tmpNode;
+            subModule.setOrganization(String.valueOf(ctx.string().getText()));
+            break;
+        }
+        default:
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                             ParsableDataType.ORGANIZATION_DATA,
+                                                                             String.valueOf(ctx.string().getText()),
+                                                                             ListenerErrorLocation.ENTRY));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java
index b02d6f4..26bc82c 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java
@@ -16,8 +16,18 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangBelongsTo;
+import org.onosproject.yangutils.datamodel.YangImport;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -63,6 +73,39 @@
      * @param ctx context object of the grammar rule.
      */
     public static void processPrefixEntry(TreeWalkListener listener, GeneratedYangParser.PrefixStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.PREFIX_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.ENTRY);
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+        case MODULE_DATA: {
+            YangModule module = (YangModule) tmpNode;
+            module.setPrefix(ctx.IDENTIFIER().getText());
+            break;
+        }
+        case IMPORT_DATA: {
+            YangImport importNode = (YangImport) tmpNode;
+            importNode.setPrefixId(ctx.IDENTIFIER().getText());
+            break;
+        }
+        case BELONGS_TO_DATA: {
+            YangBelongsTo belongstoNode = (YangBelongsTo) tmpNode;
+            belongstoNode.setPrefix(ctx.IDENTIFIER().getText());
+            break;
+        }
+        default:
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                             ParsableDataType.PREFIX_DATA, String
+                                                                                     .valueOf(ctx.IDENTIFIER()
+                                                                                             .getText()),
+                                                                             ListenerErrorLocation.ENTRY));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java
index c3233ef..3f60aef 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangImport;
+import org.onosproject.yangutils.datamodel.YangInclude;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -69,6 +78,34 @@
      */
     public static void processRevisionDateEntry(TreeWalkListener listener,
                                                 GeneratedYangParser.RevisionDateStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.REVISION_DATE_DATA,
+                                                String.valueOf(ctx.DATE_ARG().getText()),
+                                                ListenerErrorLocation.ENTRY);
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+        case IMPORT_DATA: {
+            YangImport importNode = (YangImport) tmpNode;
+            importNode.setRevision(String.valueOf(ctx.DATE_ARG().getText()));
+            break;
+        }
+        case INCLUDE_DATA: {
+            YangInclude includeNode = (YangInclude) tmpNode;
+            includeNode.setRevision(String.valueOf(ctx.DATE_ARG().getText()));
+            break;
+        }
+        default:
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                             ParsableDataType.REVISION_DATE_DATA,
+                                                                             String.valueOf(ctx.DATE_ARG().getText()),
+                                                                             ListenerErrorLocation.ENTRY));
+        }
     }
-}
+    // TODO Implement the DATE_ARG validation as per RFC 6020.
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java
index c473c83..0da2f01 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java
@@ -16,8 +16,18 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangRevision;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -59,17 +69,25 @@
     private RevisionListener() {
     }
 
-    /**
-     * It is called when parser receives an input matching the grammar
-     * rule (revision), perform validations and update the data model
-     * tree.
-     *
-     * @param listener Listener's object.
-     * @param ctx context object of the grammar rule.
-     */
-    public static void processRevisionEntry(TreeWalkListener listener, GeneratedYangParser.RevisionStatementContext
-            ctx) {
-        // TODO method implementation
+    public static void processRevisionEntry(TreeWalkListener listener,
+                                            GeneratedYangParser.RevisionStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.REVISION_DATA,
+                                                String.valueOf(ctx.DATE_ARG().getText()),
+                                                ListenerErrorLocation.ENTRY);
+
+        // Validate for reverse chronological order of revision & for revision value.
+        if (!validateRevision(listener, ctx)) {
+            return;
+            // TODO to be implemented.
+        }
+
+        YangRevision revisionNode = new YangRevision();
+        revisionNode.setRevDate(String.valueOf(ctx.DATE_ARG().getText()));
+
+        listener.getParsedDataStack().push(revisionNode);
     }
 
     /**
@@ -79,8 +97,66 @@
      * @param listener Listener's object.
      * @param ctx context object of the grammar rule.
      */
-    public static void processRevisionExit(TreeWalkListener listener, GeneratedYangParser.RevisionStatementContext
-            ctx) {
-        // TODO method implementation
+    public static void processRevisionExit(TreeWalkListener listener,
+                                           GeneratedYangParser.RevisionStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        ListenerValidation
+                .checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER, ParsableDataType.REVISION_DATA,
+                                      String.valueOf(ctx.DATE_ARG().getText()), ListenerErrorLocation.EXIT);
+
+        Parsable tmpRevisionNode = listener.getParsedDataStack().peek();
+        if (tmpRevisionNode instanceof YangRevision) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                    ParsableDataType.REVISION_DATA,
+                                                    String.valueOf(ctx.DATE_ARG().getText()),
+                                                    ListenerErrorLocation.EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getParsableDataType()) {
+            case MODULE_DATA: {
+                YangModule module = (YangModule) tmpNode;
+                module.setRevision((YangRevision) tmpRevisionNode);
+                break;
+            }
+            case SUB_MODULE_DATA: {
+                YangSubModule subModule = (YangSubModule) tmpNode;
+                subModule.setRevision((YangRevision) tmpRevisionNode);
+                break;
+            }
+            default:
+                throw new ParserException(
+                                          ListenerErrorMessageConstruction
+                                                  .constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                                                                                 ParsableDataType.REVISION_DATA,
+                                                                                 String.valueOf(ctx.DATE_ARG()
+                                                                                         .getText()),
+                                                                                 ListenerErrorLocation.EXIT));
+            }
+        } else {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.MISSING_CURRENT_HOLDER,
+                                                                             ParsableDataType.REVISION_DATA, String
+                                                                                     .valueOf(ctx.DATE_ARG()
+                                                                                             .getText()),
+                                                                             ListenerErrorLocation.EXIT));
+        }
     }
-}
+
+    /**
+     * Validate revision.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     * @return validation result
+     */
+    private static boolean validateRevision(TreeWalkListener listener,
+                                            GeneratedYangParser.RevisionStatementContext ctx) {
+        // TODO to be implemented
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
index 25f2764..3f6fc40 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
@@ -16,8 +16,15 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -60,7 +67,16 @@
      */
     public static void processSubModuleEntry(TreeWalkListener listener,
                                              GeneratedYangParser.SubModuleStatementContext ctx) {
-        // TODO method implementation
+
+        // Check if stack is empty.
+        ListenerValidation
+                .checkStackIsEmpty(listener, ListenerErrorType.INVALID_HOLDER, ParsableDataType.SUB_MODULE_DATA,
+                                   String.valueOf(ctx.IDENTIFIER().getText()), ListenerErrorLocation.ENTRY);
+
+        YangSubModule yangSubModule = new YangSubModule();
+        yangSubModule.setName(ctx.IDENTIFIER().getText());
+
+        listener.getParsedDataStack().push(yangSubModule);
     }
 
     /**
@@ -72,6 +88,21 @@
      */
     public static void processSubModuleExit(TreeWalkListener listener,
                                             GeneratedYangParser.SubModuleStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation.checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER,
+                                                ParsableDataType.SUB_MODULE_DATA,
+                                                String.valueOf(ctx.IDENTIFIER().getText()),
+                                                ListenerErrorLocation.EXIT);
+
+        if (!(listener.getParsedDataStack().peek() instanceof YangSubModule)) {
+            throw new ParserException(
+                                      ListenerErrorMessageConstruction
+                                              .constructListenerErrorMessage(ListenerErrorType.MISSING_CURRENT_HOLDER,
+                                                                             ParsableDataType.SUB_MODULE_DATA,
+                                                                             String.valueOf(ctx.IDENTIFIER()
+                                                                                     .getText()),
+                                                                             ListenerErrorLocation.EXIT));
+        }
     }
-}
+}
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
index 02afdcf..ae9389f 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
@@ -16,8 +16,17 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
@@ -73,6 +82,48 @@
      */
     public static void processVersionEntry(TreeWalkListener listener,
                                            GeneratedYangParser.YangVersionStatementContext ctx) {
-        // TODO method implementation
+
+        // Check for stack to be non empty.
+        ListenerValidation
+                .checkStackIsNotEmpty(listener, ListenerErrorType.MISSING_HOLDER, ParsableDataType.VERSION_DATA,
+                                      String.valueOf(ctx.INTEGER().getText()), ListenerErrorLocation.ENTRY);
+
+        Integer version = Integer.valueOf(ctx.INTEGER().getText());
+        if (!isVersionValid(version)) {
+            ParserException parserException = new ParserException("Input version not supported");
+            parserException.setLine(ctx.INTEGER().getSymbol().getLine());
+            parserException.setCharPosition(ctx.INTEGER().getSymbol().getCharPositionInLine());
+            throw parserException;
+        }
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+        case MODULE_DATA: {
+            YangModule module = (YangModule) tmpNode;
+            module.setVersion((byte) 1);
+            break;
+        }
+        case SUB_MODULE_DATA: {
+            YangSubModule subModule = (YangSubModule) tmpNode;
+            subModule.setVersion((byte) 1);
+            break;
+        }
+        default:
+            throw new ParserException(ListenerErrorMessageConstruction.
+                    constructListenerErrorMessage(ListenerErrorType.INVALID_HOLDER,
+                            ParsableDataType.VERSION_DATA, String.valueOf(ctx.INTEGER().getText()),
+                            ListenerErrorLocation.ENTRY));
+        }
     }
-}
+
+    /**
+     * Validates whether the value of YANG version.
+     *
+     * @param version input yang version
+     * @return validation result
+     */
+    private static boolean isVersionValid(Integer version) {
+        return version == 1;
+    }
+}
\ No newline at end of file