Fixing https://github.com/wso2/product-iots/issues/1376.

components/device-mgt/org.wso2.carbon.device.mgt.api/src/main/java/org/wso2/carbon/device/mgt/jaxrs/service/impl/GroupManagementServiceImpl.java

@@ -29,10 +29,7 @@ import org.wso2.carbon.device.mgt.common.DeviceIdentifier;
 import org.wso2.carbon.device.mgt.common.DeviceNotFoundException;
 import org.wso2.carbon.device.mgt.common.GroupPaginationRequest;
 import org.wso2.carbon.device.mgt.common.PaginationResult;
-import org.wso2.carbon.device.mgt.common.group.mgt.DeviceGroup;
+import org.wso2.carbon.device.mgt.common.group.mgt.*;
-import org.wso2.carbon.device.mgt.common.group.mgt.GroupAlreadyExistException;
-import org.wso2.carbon.device.mgt.common.group.mgt.GroupManagementException;
-import org.wso2.carbon.device.mgt.common.group.mgt.RoleDoesNotExistException;
 import org.wso2.carbon.device.mgt.core.service.GroupManagementProviderService;
 import org.wso2.carbon.device.mgt.jaxrs.beans.DeviceGroupList;
 import org.wso2.carbon.device.mgt.jaxrs.beans.DeviceList;
@@ -144,7 +141,7 @@ public class GroupManagementServiceImpl implements GroupManagementService {
             String msg = "Error occurred while adding new group.";
             log.error(msg, e);
             return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity(msg).build();
-        } catch (GroupAlreadyExistException e) {
+        } catch (GroupNotExistException e) {
             String msg = "There is another group already exists with name '" + deviceGroup.getName() + "'.";
             log.warn(msg);
             return Response.status(Response.Status.CONFLICT).entity(msg).build();

components/device-mgt/org.wso2.carbon.device.mgt.common/src/main/java/org/wso2/carbon/device/mgt/common/group/mgt/GroupNotExistException.java

@@ -0,0 +1,55 @@
+/*
+*  Copyright (c) 2017, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+*  WSO2 Inc. licenses this file to you 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.wso2.carbon.device.mgt.common.group.mgt;
+
+public class GroupNotExistException extends Exception{
+
+    private String errorMessage;
+
+    public GroupNotExistException(String msg, Exception nestedEx) {
+        super(msg, nestedEx);
+        setErrorMessage(msg);
+    }
+
+    public GroupNotExistException(String message, Throwable cause) {
+        super(message, cause);
+        setErrorMessage(message);
+    }
+
+    public GroupNotExistException(String msg) {
+        super(msg);
+        setErrorMessage(msg);
+    }
+
+    public GroupNotExistException() {
+        super();
+    }
+
+    public GroupNotExistException(Throwable cause) {
+        super(cause);
+    }
+
+    public String getErrorMessage() {
+        return errorMessage;
+    }
+
+    public void setErrorMessage(String errorMessage) {
+        this.errorMessage = errorMessage;
+    }
+
+}

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/service/GroupManagementProviderService.java

@@ -23,10 +23,7 @@ import org.wso2.carbon.device.mgt.common.DeviceIdentifier;
 import org.wso2.carbon.device.mgt.common.DeviceNotFoundException;
 import org.wso2.carbon.device.mgt.common.GroupPaginationRequest;
 import org.wso2.carbon.device.mgt.common.PaginationResult;
-import org.wso2.carbon.device.mgt.common.group.mgt.DeviceGroup;
+import org.wso2.carbon.device.mgt.common.group.mgt.*;
-import org.wso2.carbon.device.mgt.common.group.mgt.GroupAlreadyExistException;
-import org.wso2.carbon.device.mgt.common.group.mgt.GroupManagementException;
-import org.wso2.carbon.device.mgt.common.group.mgt.RoleDoesNotExistException;
 
 import java.util.List;
 
@@ -53,7 +50,7 @@ public interface GroupManagementProviderService {
      * @param groupId of the group.
      * @throws GroupManagementException
      */
-    void updateGroup(DeviceGroup deviceGroup, int groupId) throws GroupManagementException, GroupAlreadyExistException;
+    void updateGroup(DeviceGroup deviceGroup, int groupId) throws GroupManagementException, GroupNotExistException;
 
     /**
      * Delete existing device group.

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/service/GroupManagementProviderServiceImpl.java

@@ -73,9 +73,6 @@ public class GroupManagementProviderServiceImpl implements GroupManagementProvid
         if (log.isDebugEnabled()) {
             log.debug("Creating group '" + deviceGroup.getName() + "'");
         }
-        if (deviceGroup == null) {
-            throw new GroupManagementException("DeviceGroup cannot be null.", new NullPointerException());
-        }
         int tenantId = CarbonContext.getThreadLocalCarbonContext().getTenantId();
         try {
             GroupManagementDAOFactory.beginTransaction();
@@ -95,6 +92,8 @@ public class GroupManagementProviderServiceImpl implements GroupManagementProvid
             String msg = "Error occurred while initiating transaction.";
             log.error(msg, e);
             throw new GroupManagementException(msg, e);
+        } catch (GroupAlreadyExistException ex) {
+            throw ex;
         } catch (Exception e) {
             String msg = "Error occurred in creating group '" + deviceGroup.getName() + "'";
             log.error(msg, e);
@@ -113,7 +112,7 @@ public class GroupManagementProviderServiceImpl implements GroupManagementProvid
      */
     @Override
     public void updateGroup(DeviceGroup deviceGroup, int groupId)
-            throws GroupManagementException, GroupAlreadyExistException {
+            throws GroupManagementException, GroupNotExistException {
         if (deviceGroup == null) {
             String msg = "Received incomplete data for updateGroup";
             log.error(msg);
@@ -122,30 +121,29 @@ public class GroupManagementProviderServiceImpl implements GroupManagementProvid
         if (log.isDebugEnabled()) {
             log.debug("update group '" + deviceGroup.getName() + "'");
         }
-        if (deviceGroup == null) {
-            throw new GroupManagementException("DeviceGroup cannot be null.", new NullPointerException());
-        }
         try {
             int tenantId = CarbonContext.getThreadLocalCarbonContext().getTenantId();
             GroupManagementDAOFactory.beginTransaction();
-            DeviceGroup existingGroup = this.groupDAO.getGroup(deviceGroup.getName(), tenantId);
+            DeviceGroup existingGroup = this.groupDAO.getGroup(groupId, tenantId);
-            if (existingGroup == null || existingGroup.getGroupId() == groupId) {
+            if (existingGroup != null) {
                 this.groupDAO.updateGroup(deviceGroup, groupId, tenantId);
                 GroupManagementDAOFactory.commitTransaction();
             } else {
-                throw new GroupAlreadyExistException("Group exist with name " + deviceGroup.getName());
+                throw new GroupNotExistException("Group with ID - '" + groupId + "' doesn't exists!");
             }
         } catch (GroupManagementDAOException e) {
             GroupManagementDAOFactory.rollbackTransaction();
-            String msg = "Error occurred while modifying deviceGroup '" + deviceGroup.getName() + "'.";
+            String msg = "Error occurred while modifying device group with ID - '" + groupId + "'.";
             log.error(msg, e);
             throw new GroupManagementException(msg, e);
         } catch (TransactionManagementException e) {
             String msg = "Error occurred while initiating transaction.";
             log.error(msg, e);
             throw new GroupManagementException(msg, e);
+        } catch (GroupNotExistException ex) {
+            throw ex;
         } catch (Exception e) {
-            String msg = "Error occurred in updating group '" + deviceGroup.getName() + "'";
+            String msg = "Error occurred in updating the device group with ID - '" + groupId + "'.";
             log.error(msg, e);
             throw new GroupManagementException(msg, e);
         } finally {