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

Change-Id: I0f828adb5884c2d7b6e4120f9843c416608ae5e7

@@ -17,11 +17,12 @@ package org.onosproject.yangutils.datamodel;
 
 import java.util.LinkedList;
 import java.util.List;
-
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.utils.YangConstructType;
 
+import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCollidingChildUtil;
+
 /*-
  * Reference RFC 6020.
  *
@@ -76,7 +77,7 @@ import org.onosproject.yangutils.utils.YangConstructType;
  * Data model node to maintain information defined in YANG grouping.
  */
 public class YangGrouping extends YangNode
-        implements YangLeavesHolder, YangCommonInfo, Parsable {
+        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector {
 
     /**
      * Name of the grouping.
@@ -113,6 +114,8 @@ public class YangGrouping extends YangNode
      */
     public YangGrouping() {
         super(YangNodeType.GROUPING_NODE);
+        listOfLeaf = new LinkedList<YangLeaf>();
+        listOfLeafList = new LinkedList<YangLeafList>();
     }
 
     /**
@@ -181,10 +184,6 @@ public class YangGrouping extends YangNode
      */
     @Override
     public void addLeaf(YangLeaf leaf) {
-        if (getListOfLeaf() == null) {
-            setListOfLeaf(new LinkedList<YangLeaf>());
-        }
-
         getListOfLeaf().add(leaf);
     }
 
@@ -214,10 +213,6 @@ public class YangGrouping extends YangNode
      */
     @Override
     public void addLeafList(YangLeafList leafList) {
-        if (getListOfLeafList() == null) {
-            setListOfLeafList(new LinkedList<YangLeafList>());
-        }
-
         getListOfLeafList().add(leafList);
     }
 
@@ -290,4 +285,31 @@ public class YangGrouping extends YangNode
     public void validateDataOnExit() throws DataModelException {
         // TODO auto-generated method stub, to be implemented by parser
     }
+
+    /*
+     * Reference RFC6020
+     *
+     * Once a grouping is defined, it can be referenced in a "uses"
+     * statement (see Section 7.12).  A grouping MUST NOT reference itself,
+     * neither directly nor indirectly through a chain of other groupings.
+     *
+     * If the grouping is defined at the top level of a YANG module or
+     * submodule, the grouping's identifier MUST be unique within the
+     * module.
+     */
+    @Override
+    public void detectCollidingChild(String identifierName, YangConstructType dataType) throws DataModelException {
+
+        // Asks helper to detect colliding child.
+        detectCollidingChildUtil(identifierName, dataType, this);
+    }
+
+    @Override
+    public void detectSelfCollision(String identifierName, YangConstructType dataType) throws DataModelException {
+        if (getName().equals(identifierName)) {
+            throw new DataModelException("YANG file error: Duplicate input identifier detected, same as grouping \"" +
+                    getName() + "\"");
+        }
+    }
+    // TODO  A grouping MUST NOT reference itself, neither directly nor indirectly through a chain of other groupings.
 }

+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.datamodel;
+
+/**
+ * YANG node identifier which is a combination of prefix and name.
+ */
+public class YangNodeIdentifier {
+
+    // Name of the node.
+    String name;
+
+    // Prefix of the node.
+    String prefix;
+
+    /**
+     * Creates an instance of YANG node identifier.
+     */
+    public YangNodeIdentifier() {
+    }
+
+    /**
+     * Returns name of the node identifier.
+     *
+     * @return name of the node identifier
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * Set name of the node identifier.
+     *
+     * @param name node identifier name
+     */
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    /**
+     * Returns prefix of the node identifier.
+     *
+     * @return prefix of the node identifier
+     */
+    public String getPrefix() {
+        return prefix;
+    }
+
+    /**
+     * Set prefix of the node identifier.
+     *
+     * @param prefix prefix of the node identifier
+     */
+    public void setPrefix(String prefix) {
+        this.prefix = prefix;
+    }
+}

@@ -20,6 +20,7 @@ import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.utils.YangConstructType;
 
+import java.util.LinkedList;
 import java.util.List;
 
 /*
@@ -52,13 +53,14 @@ public class YangUnion implements Parsable {
     // List of YANG type.
     private List<YangType<?>> typeList;
 
-    // Name of the union.
+    // Name of union.
     private String unionName;
 
     /**
      * Create a YANG union node.
      */
     public YangUnion() {
+        typeList = new LinkedList<>();
     }
 
     /**
@@ -89,6 +91,21 @@ public class YangUnion implements Parsable {
     }
 
     /**
+     * Add YANG type to type list.
+     *
+     * @param yangType YANG type to be added to list
+     * @throws DataModelException union member type must not be one of the
+     * built-in types "empty" or "leafref"
+     */
+    public void addToTypeList(YangType<?> yangType) throws DataModelException {
+        if (yangType.getDataType() == YangDataTypes.EMPTY || yangType.getDataType() == YangDataTypes.LEAFREF) {
+            throw new DataModelException("Union member type must not be one of the built-in types \"empty\" or " +
+                    "\"leafref\"");
+        }
+        getTypeList().add(yangType);
+    }
+
+    /**
      * Set the union name.
      *
      * @param unionName name of the union.

@@ -55,17 +55,17 @@ import org.onosproject.yangutils.utils.YangConstructType;
 public class YangUses extends YangNode implements YangCommonInfo, Parsable {
 
     /**
-     * Name.
+     * Name of YANG uses.
      */
     private String name;
 
     /**
-     * referred group.
+     * Referred group.
      */
     private YangGrouping refGroup;
 
     /**
-     * description.
+     * Description of YANG uses.
      */
     private String description;
 
@@ -75,7 +75,7 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
     private String reference;
 
     /**
-     * Status.
+     * Status of YANG uses.
      */
     private YangStatusType status;
 
@@ -87,7 +87,7 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
     }
 
     /**
-     * Get the name.
+     * Returns the name.
      *
      * @return the name
      */
@@ -105,7 +105,7 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
     }
 
     /**
-     * Get the referred group.
+     * Returns the referred group.
      *
      * @return the referred group
      */
@@ -123,7 +123,7 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
     }
 
     /**
-     * Get the description.
+     * Returns the description.
      *
      * @return the description
      */
@@ -143,7 +143,7 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
     }
 
     /**
-     * Get the textual reference.
+     * Returns the textual reference.
      *
      * @return the reference
      */
@@ -163,7 +163,7 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
     }
 
     /**
-     * Get the status.
+     * Returns the status.
      *
      * @return the status
      */
@@ -212,26 +212,14 @@ public class YangUses extends YangNode implements YangCommonInfo, Parsable {
         // TODO auto-generated method stub, to be implemented by parser
     }
 
-    /**
-     * Get uses name.
-     *
-     * @return uses name
-     */
     @Override
     public String getName() {
-        // TODO Auto-generated method stub
-        return null;
+        return name;
     }
 
-    /**
-     * Set uses name.
-     *
-     * @param name uses name
-     */
     @Override
     public void setName(String name) {
-        // TODO Auto-generated method stub
-
+        this.name = name;
     }
 
 }

@@ -38,6 +38,7 @@ import org.onosproject.yangutils.parser.impl.listeners.DefaultListener;
 import org.onosproject.yangutils.parser.impl.listeners.DescriptionListener;
 import org.onosproject.yangutils.parser.impl.listeners.EnumListener;
 import org.onosproject.yangutils.parser.impl.listeners.EnumerationListener;
+import org.onosproject.yangutils.parser.impl.listeners.GroupingListener;
 import org.onosproject.yangutils.parser.impl.listeners.ImportListener;
 import org.onosproject.yangutils.parser.impl.listeners.IncludeListener;
 import org.onosproject.yangutils.parser.impl.listeners.KeyListener;
@@ -61,7 +62,9 @@ import org.onosproject.yangutils.parser.impl.listeners.StatusListener;
 import org.onosproject.yangutils.parser.impl.listeners.SubModuleListener;
 import org.onosproject.yangutils.parser.impl.listeners.TypeDefListener;
 import org.onosproject.yangutils.parser.impl.listeners.TypeListener;
+import org.onosproject.yangutils.parser.impl.listeners.UnionListener;
 import org.onosproject.yangutils.parser.impl.listeners.UnitsListener;
+import org.onosproject.yangutils.parser.impl.listeners.UsesListener;
 import org.onosproject.yangutils.parser.impl.listeners.ValueListener;
 import org.onosproject.yangutils.parser.impl.listeners.VersionListener;
 
@@ -687,12 +690,12 @@ public class TreeWalkListener implements GeneratedYangListener {
 
     @Override
     public void enterUnionSpecification(GeneratedYangParser.UnionSpecificationContext ctx) {
-        // TODO: implement the method.
+        UnionListener.processUnionEntry(this, ctx);
     }
 
     @Override
     public void exitUnionSpecification(GeneratedYangParser.UnionSpecificationContext ctx) {
-        // TODO: implement the method.
+        UnionListener.processUnionExit(this, ctx);
     }
 
     @Override
@@ -847,12 +850,12 @@ public class TreeWalkListener implements GeneratedYangListener {
 
     @Override
     public void enterGroupingStatement(GeneratedYangParser.GroupingStatementContext ctx) {
-        // TODO: implement the method.
+        GroupingListener.processGroupingEntry(this, ctx);
     }
 
     @Override
     public void exitGroupingStatement(GeneratedYangParser.GroupingStatementContext ctx) {
-        // TODO: implement the method.
+        GroupingListener.processGroupingExit(this, ctx);
     }
 
     @Override
@@ -947,12 +950,12 @@ public class TreeWalkListener implements GeneratedYangListener {
 
     @Override
     public void enterUsesStatement(GeneratedYangParser.UsesStatementContext ctx) {
-        // TODO: implement the method.
+        UsesListener.processUsesEntry(this, ctx);
     }
 
     @Override
     public void exitUsesStatement(GeneratedYangParser.UsesStatementContext ctx) {
-        // TODO: implement the method.
+        UsesListener.processUsesExit(this, ctx);
     }
 
     @Override

@@ -16,6 +16,7 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangCase;
 import org.onosproject.yangutils.datamodel.YangContainer;
 import org.onosproject.yangutils.datamodel.YangList;
 import org.onosproject.yangutils.datamodel.YangModule;
@@ -126,7 +127,7 @@ public final class ContainerListener {
 
         Parsable curData = listener.getParsedDataStack().peek();
         if (curData instanceof YangModule || curData instanceof YangContainer
-                || curData instanceof YangList) {
+                || curData instanceof YangList || curData instanceof YangCase) {
             YangNode curNode = (YangNode) curData;
             try {
                 curNode.addChild(container);

@@ -45,6 +45,7 @@ import org.onosproject.yangutils.datamodel.YangEnumeration;
 import org.onosproject.yangutils.datamodel.YangLeaf;
 import org.onosproject.yangutils.datamodel.YangLeafList;
 import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.datamodel.YangUnion;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
@@ -102,7 +103,10 @@ public final class EnumerationListener {
                 case LEAF_LIST_DATA:
                     enumerationNode.setEnumerationName(((YangLeafList) tmpData).getLeafName());
                     break;
-                // TODO typedef, union, deviate.
+                case UNION_DATA:
+                    enumerationNode.setEnumerationName(((YangUnion) tmpData).getUnionName());
+                    break;
+                // TODO typedef, deviate.
                 default:
                     throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, TYPE_DATA,
                             ((YangType<?>) typeData).getDataTypeName(), ENTRY));

+/*
+ * Copyright 2014-2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangGrouping;
+import org.onosproject.yangutils.datamodel.YangInput;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNotification;
+import org.onosproject.yangutils.datamodel.YangOutput;
+import org.onosproject.yangutils.datamodel.YangRpc;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+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;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.datamodel.utils.GeneratedLanguage.JAVA_GENERATION;
+import static org.onosproject.yangutils.datamodel.utils.YangDataModelFactory.getYangGroupingNode;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerCollisionDetector.detectCollidingChildUtil;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.UNHANDLED_PARSED_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.validateCardinalityMaxOne;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.validateMutuallyExclusiveChilds;
+import static org.onosproject.yangutils.utils.YangConstructType.DESCRIPTION_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.GROUPING_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.REFERENCE_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.STATUS_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.TYPEDEF_DATA;
+
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ * grouping-stmt       = grouping-keyword sep identifier-arg-str optsep
+ *                      (";" /
+ *                       "{" stmtsep
+ *                          ;; these stmts can appear in any order
+ *                          [status-stmt stmtsep]
+ *                           [description-stmt stmtsep]
+ *                           [reference-stmt stmtsep]
+ *                           *((typedef-stmt /
+ *                              grouping-stmt) stmtsep)
+ *                           *(data-def-stmt stmtsep)
+ *                       "}")
+ *
+ * ANTLR grammar rule
+ * groupingStatement : GROUPING_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE
+ *       (statusStatement | descriptionStatement | referenceStatement | typedefStatement | groupingStatement
+ *       | dataDefStatement)* RIGHT_CURLY_BRACE);
+ */
+
+/**
+ * Implements listener based call back function corresponding to the "grouping"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class GroupingListener {
+
+    /**
+     * Creates a new grouping listener.
+     */
+    private GroupingListener() {
+    }
+
+    /**
+     * It is called when parser enters grammar rule (grouping), it perform
+     * validations and updates the data model tree.
+     *
+     * @param listener listener's object
+     * @param ctx context object of the grammar rule
+     */
+    public static void processGroupingEntry(TreeWalkListener listener,
+                                        GeneratedYangParser.GroupingStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, GROUPING_DATA, ctx.identifier().getText(), ENTRY);
+
+        // Check validity of identifier and remove double quotes.
+        String identifier = getValidIdentifier(ctx.identifier().getText(), GROUPING_DATA, ctx);
+
+        // Validate sub statement cardinality.
+        validateSubStatementsCardinality(ctx);
+
+        Parsable curData = listener.getParsedDataStack().peek();
+
+        // Check for identifier collision
+        int line = ctx.getStart().getLine();
+        int charPositionInLine = ctx.getStart().getCharPositionInLine();
+        detectCollidingChildUtil(listener, line, charPositionInLine, identifier, GROUPING_DATA);
+
+        if (curData instanceof YangModule || curData instanceof YangSubModule
+                || curData instanceof YangContainer || curData instanceof YangNotification
+                || curData instanceof YangList || curData instanceof YangGrouping
+                || curData instanceof YangRpc || curData instanceof YangInput
+                || curData instanceof YangOutput) {
+
+            YangGrouping groupingNode = getYangGroupingNode(JAVA_GENERATION);
+            groupingNode.setName(identifier);
+
+            YangNode curNode = (YangNode) curData;
+            try {
+                curNode.addChild(groupingNode);
+            } catch (DataModelException e) {
+                throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
+                        GROUPING_DATA, ctx.identifier().getText(), ENTRY, e.getMessage()));
+            }
+            listener.getParsedDataStack().push(groupingNode);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER,
+                    GROUPING_DATA, ctx.identifier().getText(), ENTRY));
+        }
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (grouping), it perform
+     * validations and update the data model tree.
+     *
+     * @param listener Listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processGroupingExit(TreeWalkListener listener,
+                                         GeneratedYangParser.GroupingStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, GROUPING_DATA, ctx.identifier().getText(), EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangGrouping) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, GROUPING_DATA,
+                    ctx.identifier().getText(), EXIT));
+        }
+    }
+
+    /**
+     * Validates the cardinality of case sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule
+     */
+    private static void validateSubStatementsCardinality(GeneratedYangParser.GroupingStatementContext ctx) {
+
+        validateCardinalityMaxOne(ctx.statusStatement(), STATUS_DATA, GROUPING_DATA, ctx.identifier().getText());
+        validateCardinalityMaxOne(ctx.descriptionStatement(), DESCRIPTION_DATA, GROUPING_DATA,
+                ctx.identifier().getText());
+        validateCardinalityMaxOne(ctx.referenceStatement(), REFERENCE_DATA, GROUPING_DATA, ctx.identifier().getText());
+        validateMutuallyExclusiveChilds(ctx.typedefStatement(), TYPEDEF_DATA, ctx.groupingStatement(), GROUPING_DATA,
+                GROUPING_DATA, ctx.identifier().getText());
+    }
+}

@@ -16,6 +16,7 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.onosproject.yangutils.datamodel.YangCase;
 import org.onosproject.yangutils.datamodel.YangContainer;
 import org.onosproject.yangutils.datamodel.YangList;
 import org.onosproject.yangutils.datamodel.YangModule;
@@ -133,7 +134,7 @@ public final class ListListener {
 
         Parsable curData = listener.getParsedDataStack().peek();
         if (curData instanceof YangModule || curData instanceof YangContainer
-                || curData instanceof YangList) {
+                || curData instanceof YangList || curData instanceof YangCase) {
             curNode = (YangNode) curData;
             try {
                 curNode.addChild(yangList);

@@ -22,6 +22,8 @@ import org.onosproject.yangutils.datamodel.YangLeaf;
 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 @@ public final class TypeListener {
                 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 */

+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ * type-body-stmts     = numerical-restrictions /
+ *                       decimal64-specification /
+ *                      string-restrictions /
+ *                       enum-specification /
+ *                       leafref-specification /
+ *                       identityref-specification /
+ *                       instance-identifier-specification /
+ *                       bits-specification /
+ *                       union-specification
+ *
+ * union-specification = 1*(type-stmt stmtsep)
+ *
+ * ANTLR grammar rule
+ * typeBodyStatements : numericalRestrictions | stringRestrictions | enumSpecification
+ *                 | leafrefSpecification | identityrefSpecification | instanceIdentifierSpecification
+ *                 | bitsSpecification | unionSpecification;
+ *
+ * unionSpecification : typeStatement+;
+ */
+
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.datamodel.YangUnion;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+import static org.onosproject.yangutils.utils.YangConstructType.TYPE_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.UNION_DATA;
+
+/**
+ * Implements listener based call back function corresponding to the "union" rule
+ * defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class UnionListener {
+    /**
+     * Creates a new union listener.
+     */
+    private UnionListener() {
+    }
+
+    /**
+     * It is called when parser enters grammar rule (union), it perform
+     * validations and updates the data model tree.
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processUnionEntry(TreeWalkListener listener,
+                                         GeneratedYangParser.UnionSpecificationContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, UNION_DATA, "", ENTRY);
+
+        if (listener.getParsedDataStack().peek() instanceof YangType) {
+            YangUnion unionNode = new YangUnion();
+            Parsable typeData = listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, UNION_DATA, "", ENTRY);
+
+            Parsable tmpData = listener.getParsedDataStack().peek();
+
+            switch (tmpData.getYangConstructType()) {
+                case LEAF_DATA:
+                    unionNode.setUnionName(((YangLeaf) tmpData).getLeafName());
+                    break;
+                case LEAF_LIST_DATA:
+                    unionNode.setUnionName(((YangLeafList) tmpData).getLeafName());
+                    break;
+                case UNION_DATA:
+                    unionNode.setUnionName(((YangUnion) tmpData).getUnionName());
+                    break;
+                // TODO typedef, deviate.
+                default:
+                    throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, TYPE_DATA,
+                            ((YangType<?>) typeData).getDataTypeName(), ENTRY));
+            }
+            listener.getParsedDataStack().push(typeData);
+            listener.getParsedDataStack().push(unionNode);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, UNION_DATA, "", ENTRY));
+        }
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (union), it perform
+     * validations and update the data model tree.
+     *
+     * @param listener Listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processUnionExit(TreeWalkListener listener,
+                                       GeneratedYangParser.UnionSpecificationContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, UNION_DATA, "", EXIT);
+
+        Parsable tmpUnionNode = listener.getParsedDataStack().peek();
+        if (tmpUnionNode instanceof YangUnion) {
+            YangUnion unionNode = (YangUnion) tmpUnionNode;
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, UNION_DATA, "", EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getYangConstructType()) {
+                case TYPE_DATA: {
+                    YangType<YangUnion> typeNode = (YangType<YangUnion>) tmpNode;
+                    typeNode.setDataTypeExtendedInfo(unionNode);
+                    break;
+                }
+                default:
+                    throw new ParserException(
+                            constructListenerErrorMessage(INVALID_HOLDER, UNION_DATA, "", EXIT));
+            }
+        } else {
+            throw new ParserException(
+                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, UNION_DATA, "", EXIT));
+        }
+    }
+}
\ No newline at end of file

+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.onosproject.yangutils.datamodel.YangAugment;
+import org.onosproject.yangutils.datamodel.YangCase;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangGrouping;
+import org.onosproject.yangutils.datamodel.YangInput;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNotification;
+import org.onosproject.yangutils.datamodel.YangOutput;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.datamodel.YangUses;
+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;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.datamodel.utils.GeneratedLanguage.JAVA_GENERATION;
+import static org.onosproject.yangutils.datamodel.utils.YangDataModelFactory.getYangUsesNode;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.UNHANDLED_PARSED_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.validateCardinalityMaxOne;
+import static org.onosproject.yangutils.utils.YangConstructType.DESCRIPTION_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.REFERENCE_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.STATUS_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.USES_DATA;
+import static org.onosproject.yangutils.utils.YangConstructType.WHEN_DATA;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ * data-def-stmt       = container-stmt /
+ *                      leaf-stmt /
+ *                      leaf-list-stmt /
+ *                      list-stmt /
+ *                      choice-stmt /
+ *                      anyxml-stmt /
+ *                      uses-stmt
+ *
+ * uses-stmt           = uses-keyword sep identifier-ref-arg-str optsep
+ *                       (";" /
+ *                        "{" stmtsep
+ *                            ;; these stmts can appear in any order
+ *                            [when-stmt stmtsep]
+ *                            *(if-feature-stmt stmtsep)
+ *                            [status-stmt stmtsep]
+ *                            [description-stmt stmtsep]
+ *                            [reference-stmt stmtsep]
+ *                            *(refine-stmt stmtsep)
+ *                            *(uses-augment-stmt stmtsep)
+ *                        "}")
+ *
+ * ANTLR grammar rule
+ * dataDefStatement : containerStatement
+ *                 | leafStatement
+ *                 | leafListStatement
+ *                 | listStatement
+ *                 | choiceStatement
+ *                 | usesStatement;
+ *
+ * usesStatement : USES_KEYWORD string (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement
+ *                 | statusStatement | descriptionStatement | referenceStatement | refineStatement
+ *                 | usesAugmentStatement)* RIGHT_CURLY_BRACE);
+ */
+
+/**
+ * Implements listener based call back function corresponding to the "uses"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class UsesListener {
+
+    /**
+     * Creates a new uses listener.
+     */
+    private UsesListener() {
+    }
+
+    /**
+     * It is called when parser enters grammar rule (uses), it perform
+     * validations and updates the data model tree.
+     *
+     * @param listener listener's object
+     * @param ctx context object of the grammar rule
+     */
+    public static void processUsesEntry(TreeWalkListener listener, GeneratedYangParser.UsesStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, USES_DATA, ctx.string().getText(), ENTRY);
+
+        // Validate sub statement cardinality.
+        validateSubStatementsCardinality(ctx);
+
+        Parsable curData = listener.getParsedDataStack().peek();
+
+        if (curData instanceof YangModule || curData instanceof YangSubModule
+                || curData instanceof YangContainer || curData instanceof YangList
+                || curData instanceof YangUses || curData instanceof YangAugment
+                || curData instanceof YangCase || curData instanceof YangGrouping
+                || curData instanceof YangInput || curData instanceof YangOutput
+                || curData instanceof YangNotification) {
+
+            YangUses usesNode = getYangUsesNode(JAVA_GENERATION);
+            usesNode.setName(ctx.string().getText());
+
+            YangNode curNode = (YangNode) curData;
+
+            try {
+                curNode.addChild(usesNode);
+            } catch (DataModelException e) {
+                throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
+                        USES_DATA, ctx.string().getText(), ENTRY, e.getMessage()));
+            }
+            listener.getParsedDataStack().push(usesNode);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER,
+                    USES_DATA, ctx.string().getText(), ENTRY));
+        }
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (uses), it perform
+     * validations and update the data model tree.
+     *
+     * @param listener Listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processUsesExit(TreeWalkListener listener,
+                                           GeneratedYangParser.UsesStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, USES_DATA, ctx.string().getText(), EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangUses) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, USES_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+    }
+
+    // TODO linker to handle collision scenarios like leaf obtained by uses, conflicts with some existing leaf.
+
+    /**
+     * Validates the cardinality of case sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule
+     */
+    private static void validateSubStatementsCardinality(GeneratedYangParser.UsesStatementContext ctx) {
+        validateCardinalityMaxOne(ctx.whenStatement(), WHEN_DATA, USES_DATA, ctx.string().getText());
+        validateCardinalityMaxOne(ctx.statusStatement(), STATUS_DATA, USES_DATA, ctx.string().getText());
+        validateCardinalityMaxOne(ctx.descriptionStatement(), DESCRIPTION_DATA, USES_DATA, ctx.string().getText());
+        validateCardinalityMaxOne(ctx.referenceStatement(), REFERENCE_DATA, USES_DATA, ctx.string().getText());    }
+}

@@ -23,6 +23,7 @@ import java.text.SimpleDateFormat;
 import java.util.Calendar;
 import java.util.regex.Pattern;
 
+import org.onosproject.yangutils.datamodel.YangNodeIdentifier;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.utils.YangConstructType;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
@@ -43,6 +44,7 @@ public final class ListenerUtil {
     private static final String HYPHEN = "-";
     private static final String SLASH = "/";
     private static final String SPACE = " ";
+    private static final String COLON = ":";
 
     /**
      * Creates a new listener util.
@@ -204,4 +206,35 @@ public final class ListenerUtil {
                 EMPTY_STRING);
         return dateForRevision;
     }
+
+    /**
+     * Checks and return valid node identifier.
+     *
+     * @param nodeIdentifierString string from yang file
+     * @param yangConstruct yang construct for creating error message
+     * @param ctx yang construct's context to get the line number and character position
+     * @return valid node identifier
+     */
+    public static YangNodeIdentifier getValidNodeIdentifier(String nodeIdentifierString, YangConstructType
+            yangConstruct, ParserRuleContext ctx) {
+        String tmpIdentifierString = removeQuotesAndHandleConcat(nodeIdentifierString);
+        String[] tmpData = tmpIdentifierString.split(Pattern.quote(COLON));
+        if (tmpData.length == 1) {
+            YangNodeIdentifier nodeIdentifier = new YangNodeIdentifier();
+            nodeIdentifier.setName(getValidIdentifier(tmpData[0], yangConstruct, ctx));
+            return nodeIdentifier;
+        } else if (tmpData.length == 2) {
+            YangNodeIdentifier nodeIdentifier = new YangNodeIdentifier();
+            nodeIdentifier.setPrefix(getValidIdentifier(tmpData[0], yangConstruct, ctx));
+            nodeIdentifier.setName(getValidIdentifier(tmpData[1], yangConstruct, ctx));
+            return nodeIdentifier;
+        } else {
+            ParserException parserException = new ParserException("YANG file error : " +
+                    YangConstructType.getYangConstructType(yangConstruct) + " name " + nodeIdentifierString +
+                    " is not valid.");
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+            throw parserException;
+        }
+    }
 }
\ No newline at end of file

+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import java.io.IOException;
+import java.util.ListIterator;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangGrouping;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeType;
+import org.onosproject.yangutils.datamodel.YangStatusType;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+
+/**
+ * Test cases for testing grouping listener.
+ */
+public class GroupingListenerTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks grouping statement inside module.
+     */
+    @Test
+    public void processGroupingInModule() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/GroupingInModule.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangGrouping yangGrouping = (YangGrouping) yangNode.getChild();
+        assertThat(yangGrouping.getName(), is("endpoint"));
+
+        ListIterator<YangLeaf> leafIterator = yangGrouping.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getLeafName(), is("address"));
+    }
+
+    /**
+     * Checks grouping statement inside container.
+     */
+    @Test
+    public void processGroupingInContainer() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/GroupingInContainer.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangContainer yangContainer = (YangContainer) yangNode.getChild();
+        assertThat(yangContainer.getName(), is("valid"));
+
+        YangGrouping yangGrouping = (YangGrouping) yangContainer.getChild();
+        assertThat(yangGrouping.getName(), is("endpoint"));
+
+        ListIterator<YangLeaf> leafIterator = yangGrouping.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getLeafName(), is("address"));
+    }
+
+    /**
+     * Checks grouping statement inside list.
+     */
+    @Test
+    public void processGroupingInList() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/GroupingInList.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangList yangList = (YangList) yangNode.getChild();
+        assertThat(yangList.getName(), is("valid"));
+
+        YangGrouping yangGrouping = (YangGrouping) yangList.getChild();
+        assertThat(yangGrouping.getName(), is("endpoint"));
+
+        ListIterator<YangLeaf> leafIterator = yangGrouping.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getLeafName(), is("address"));
+    }
+
+    /**
+     * Checks grouping with attributes.
+     */
+    @Test
+    public void processGroupingAttributes() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/GroupingAttributes.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangList yangList = (YangList) yangNode.getChild();
+        assertThat(yangList.getName(), is("valid"));
+
+        YangGrouping yangGrouping = (YangGrouping) yangList.getChild();
+        assertThat(yangGrouping.getName(), is("endpoint"));
+        assertThat(yangGrouping.getStatus(), is(YangStatusType.CURRENT));
+        assertThat(yangGrouping.getReference(), is("\"RFC 6020\""));
+        assertThat(yangGrouping.getDescription(), is("\"grouping under test\""));
+
+        ListIterator<YangLeaf> leafIterator = yangGrouping.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getLeafName(), is("address"));
+    }
+
+    /**
+     * Checks duplicate grouping in list.
+     */
+    @Test(expected = ParserException.class)
+    public void processDuplicateGroupingInList() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/DuplicateGroupingInList.yang");
+    }
+
+    /**
+     * Checks duplicate grouping in container.
+     */
+    @Test (expected = ParserException.class)
+    public void processDuplicateGroupingInContainer() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/DuplicateGroupingInContainer.yang");
+    }
+
+    /**
+     * Checks duplicate grouping in module.
+     */
+    @Test (expected = ParserException.class)
+    public void processDuplicateGroupingInModule() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/DuplicateGroupingInModule.yang");
+    }
+}

+/*
+ * Copyright 2014-2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangCase;
+import org.onosproject.yangutils.datamodel.YangChoice;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeType;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import java.io.IOException;
+
+/**
+ * Test cases for short case listener.
+ */
+public class ShortCaseListenerTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks short case listener with container.
+     */
+    @Test
+    public void processShortCaseListenerWithContainer() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/ShortCaseListenerWithContainer.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangContainer yangContainer = (YangContainer) yangNode.getChild();
+        assertThat(yangContainer.getName(), is("food"));
+
+        YangChoice yangChoice = (YangChoice) yangContainer.getChild();
+        assertThat(yangChoice.getName(), is("snack"));
+
+        YangCase yangCase = (YangCase) yangChoice.getChild();
+        assertThat(yangCase.getName(), is("sports-arena"));
+
+        YangContainer yangContainer1 = (YangContainer) yangCase.getChild();
+        assertThat(yangContainer1.getName(), is("sports-arena"));
+    }
+
+    /**
+     * Checks short case listener with list.
+     */
+    @Test
+    public void processShortCaseListenerWithList() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/ShortCaseListenerWithList.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangContainer yangContainer = (YangContainer) yangNode.getChild();
+        assertThat(yangContainer.getName(), is("food"));
+
+        YangChoice yangChoice = (YangChoice) yangContainer.getChild();
+        assertThat(yangChoice.getName(), is("snack"));
+
+        YangCase yangCase = (YangCase) yangChoice.getChild();
+        assertThat(yangCase.getName(), is("sports-arena"));
+
+        YangList yangList = (YangList) yangCase.getChild();
+        assertThat(yangList.getName(), is("sports-arena"));
+    }
+}

+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.ListIterator;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangDataTypes;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeType;
+import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.datamodel.YangUnion;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+
+/**
+ * Test cases for testing union listener.
+ */
+public class UnionListenerTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks union when type is in leaf.
+     */
+    @Test
+    public void processUnionWhenTypeInLeaf() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/UnionWhenTypeInLeaf.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangList yangList = (YangList) yangNode.getChild();
+        assertThat(yangList.getName(), is("valid"));
+
+        ListIterator<YangLeaf> leafIterator = yangList.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getLeafName(), is("invalid-interval"));
+
+        assertThat(leafInfo.getDataType().getDataType(), is(YangDataTypes.UNION));
+        assertThat(leafInfo.getDataType().getDataTypeName(), is("union"));
+
+        YangUnion yangUnion = (YangUnion) leafInfo.getDataType().getDataTypeExtendedInfo();
+
+        List<YangType<?>> typeList = yangUnion.getTypeList();
+        ListIterator<YangType<?>> typeListIterator = typeList.listIterator();
+        YangType<?> yangType = typeListIterator.next();
+
+        assertThat(yangType.getDataTypeName(), is("int32"));
+        assertThat(yangType.getDataType(), is(YangDataTypes.INT32));
+
+        YangType<?> yangTypeEnum = typeListIterator.next();
+
+        assertThat(yangTypeEnum.getDataTypeName(), is("enumeration"));
+        assertThat(yangTypeEnum.getDataType(), is(YangDataTypes.ENUMERATION));
+    }
+
+    /**
+     * Checks union when type is in leaflist.
+     */
+    @Test
+    public void processUnionWhenTypeInLeafList() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/UnionWhenTypeInLeafList.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangList yangList = (YangList) yangNode.getChild();
+        assertThat(yangList.getName(), is("valid"));
+
+        ListIterator<YangLeafList> leafListIterator = yangList.getListOfLeafList().listIterator();
+        YangLeafList leafListInfo = leafListIterator.next();
+
+        assertThat(leafListInfo.getLeafName(), is("invalid-interval"));
+
+        assertThat(leafListInfo.getDataType().getDataType(), is(YangDataTypes.UNION));
+        assertThat(leafListInfo.getDataType().getDataTypeName(), is("union"));
+
+        YangUnion yangUnion = (YangUnion) leafListInfo.getDataType().getDataTypeExtendedInfo();
+
+        List<YangType<?>> typeList = yangUnion.getTypeList();
+        ListIterator<YangType<?>> typeListIterator = typeList.listIterator();
+        YangType<?> yangType = typeListIterator.next();
+
+        assertThat(yangType.getDataTypeName(), is("int32"));
+        assertThat(yangType.getDataType(), is(YangDataTypes.INT32));
+
+        YangType<?> yangTypeEnum = typeListIterator.next();
+
+        assertThat(yangTypeEnum.getDataTypeName(), is("enumeration"));
+        assertThat(yangTypeEnum.getDataType(), is(YangDataTypes.ENUMERATION));
+    }
+
+    /**
+     * Checks union with empty type.
+     */
+    @Test (expected = ParserException.class)
+    public void processUnionWithEmptyType() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/UnionWithEmptyType.yang");
+    }
+}

+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import java.io.IOException;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeType;
+import org.onosproject.yangutils.datamodel.YangStatusType;
+import org.onosproject.yangutils.datamodel.YangUses;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+
+/**
+ * Test cases for testing uses listener.
+ */
+public class UsesListenerTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks uses statement inside module.
+     */
+    @Test
+    public void processUsesInModule() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/UsesInModule.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangUses yangUses = (YangUses) yangNode.getChild();
+        assertThat(yangUses.getName(), is("endpoint"));
+    }
+
+    /**
+     * Checks uses statement inside container.
+     */
+    @Test
+    public void processUsesInContainer() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/UsesInContainer.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangContainer yangContainer = (YangContainer) yangNode.getChild();
+        assertThat(yangContainer.getName(), is("valid"));
+
+        YangUses yangUses = (YangUses) yangContainer.getChild();
+        assertThat(yangUses.getName(), is("endpoint"));
+
+        // Check attributes associated with uses.
+        assertThat(yangUses.getStatus(), is(YangStatusType.CURRENT));
+        assertThat(yangUses.getReference(), is("\"RFC 6020\""));
+        assertThat(yangUses.getDescription(), is("\"grouping under test\""));
+    }
+
+    /**
+     * Checks uses statement inside list.
+     */
+    @Test
+    public void processUsesInList() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/UsesInList.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangList yangList = (YangList) yangNode.getChild();
+        assertThat(yangList.getName(), is("valid"));
+
+        YangUses yangUses = (YangUses) yangList.getChild();
+        assertThat(yangUses.getName(), is("endpoint"));
+
+        // Check attributes associated with uses.
+        assertThat(yangUses.getStatus(), is(YangStatusType.CURRENT));
+        assertThat(yangUses.getReference(), is("\"RFC 6020\""));
+        assertThat(yangUses.getDescription(), is("\"grouping under test\""));
+    }
+}

@@ -2,22 +2,22 @@ module Test {
     yang-version 1;
     namespace http://huawei.com;
     prefix Ant;
-     container food {
-       choice snack {
-           case sports-arena {
-               leaf pretzel {
-                   type empty;
-               }
-           }
-           case late-night {
-               choice dinner {
-                  case late-night {
-                   leaf beer {
-                       type empty;
-                   }
-               }
-           }
-       }
+    container food {
+        choice snack {
+            case sports-arena {
+                leaf pretzel {
+                    type empty;
+                }
+            }
+            case late-night {
+                choice dinner {
+                    case late-night {
+                        leaf beer {
+                            type empty;
+                        }
+                    }
+                }
+            }
+        }
     }
-  }
 }

@@ -4,7 +4,7 @@ module Test {
     prefix Ant;
     container valid {
         config false;
-    	list valid {
+        list valid {
             key "invalid-interval";
             config true;
             leaf invalid-interval {

@@ -11,7 +11,7 @@ module Test {
             status current;
             reference "RFC 6020";
         }
-        container valid { 
+        container valid {
             config true;
             leaf invalid-interval {
                 type "uint16";
@@ -19,6 +19,6 @@ module Test {
                 status current;
                 reference "RFC 6020";
             }
-        }        
+        }
     }
 }
\ No newline at end of file

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container valid {
+        grouping endpoint {
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+        grouping endpoint {
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key address;
+        grouping endpoint {
+            description "grouping under test";
+            status current;
+            reference "RFC 6020";
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+        leaf address {
+            type ip;
+        }
+        grouping endpoint {
+            description "grouping under test";
+            status current;
+            reference "RFC 6020";
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    grouping endpoint {
+        leaf address {
+            type ip-address;
+        }
+        leaf port {
+            type port-number;
+        }
+    }
+    grouping endpoint {
+        leaf address {
+            type ip-address;
+        }
+        leaf port {
+            type port-number;
+        }
+    }
+}

@@ -2,22 +2,22 @@ module Test {
     yang-version 1;
     namespace http://huawei.com;
     prefix Ant;
-     container food {
-       choice snack {
-           case sports-arena {
-               leaf pretzel {
-                   type empty;
-               }
-           }
-           case late-night {
-               choice lunch {
-                  case late {
-                   leaf pretzel {
-                       type empty;
-                   }
-               }
-           }
-       }
+    container food {
+        choice snack {
+            case sports-arena {
+                leaf pretzel {
+                    type empty;
+                }
+            }
+            case late-night {
+                choice lunch {
+                    case late {
+                        leaf pretzel {
+                            type empty;
+                        }
+                    }
+                }
+            }
+        }
     }
-  }
 }

@@ -4,11 +4,11 @@ module Test {
     prefix Ant;
     leaf speed {
         type enumeration {
-          enum 10m;
-          enum 100m;
-          enum 10m {
-	     value 11;
-          }
+            enum 10m;
+            enum 100m;
+            enum 10m {
+                value 11;
+            }
         }
     }
 }

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key address;
+        leaf address {
+            type ip;
+        }
+        grouping endpoint {
+            description "grouping under test";
+            status current;
+            reference "RFC 6020";
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container valid {
+        grouping endpoint {
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key address;
+        leaf address {
+            type ip;
+        }
+        grouping endpoint {
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    grouping endpoint {
+        leaf address {
+            type ip-address;
+        }
+        leaf port {
+            type port-number;
+        }
+    }
+}

@@ -2,14 +2,14 @@ module Test {
     yang-version 1;
     namespace http://huawei.com;
     prefix Ant;
-     container food {
-       choice snack {
-           container sports-arena {
-               leaf pretzel {
-                   type empty;
-               }
-           }
-       }
+        container food {
+            choice snack {
+                container sports-arena {
+                    leaf pretzel {
+                        type empty;
+                    }
+                }
+            }
+        }
     }
-  }
 }

@@ -2,15 +2,15 @@ module Test {
     yang-version 1;
     namespace http://huawei.com;
     prefix Ant;
-     container food {
-       choice snack {
-           list sports-arena {
-               key "pretzel";
-               leaf pretzel {
-                   type int32;
-               }
-           }
-       }
+        container food {
+            choice snack {
+                list sports-arena {
+                    key "pretzel";
+                    leaf pretzel {
+                        type int32;
+                    }
+                }
+            }
+        }
     }
-  }
 }

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key "invalid-interval";
+        leaf invalid-interval {
+            type union {
+                type int32;
+                type enumeration {
+                    enum "unbounded";
+                }
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key "invalid-interval";
+        leaf-list invalid-interval {
+            type union {
+            type int32;
+            type enumeration {
+                    enum "unbounded";
+                }
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key "invalid-interval";
+        leaf invalid-interval {
+            type union {
+                type empty;
+                type enumeration {
+                    enum "unbounded";
+                }
+            }
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container valid {
+        uses endpoint {
+            description "grouping under test";
+            status current;
+            reference "RFC 6020";
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list valid {
+        key address;
+        leaf address {
+            type ip;
+        }
+        uses endpoint {
+            description "grouping under test";
+            status current;
+            reference "RFC 6020";
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    uses endpoint;
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    grouping endpoint {
+        leaf address {
+            type ip-address;
+        }
+    leaf port {
+        type port-number;
+        }
+    }
+    container valid {
+        grouping endpoint {
+            leaf address {
+                type ip-address;
+            }
+            leaf port {
+                type port-number;
+            }
+        }
+    }
+}

@@ -4,13 +4,13 @@ module Test {
     prefix Ant;
     leaf speed {
         type enumeration {
-          enum 10m {
-	     value 10;
-          }
-          enum 100m;
-          enum auto {
-	     value 1000;
-          }
+            enum 10m {
+                value 10;
+            }
+            enum 100m;
+            enum auto {
+                value 1000;
+            }
         }
     }
 }