Fix tag feature modifications after review

components/device-mgt/io.entgra.device.mgt.core.device.mgt.api/src/main/java/io/entgra/device/mgt/core/device/mgt/api/jaxrs/service/api/DeviceManagementService.java

@@ -338,10 +338,10 @@ public interface DeviceManagementService {
             @QueryParam("requireDeviceInfo")
                     boolean requireDeviceInfo,
             @ApiParam(
-                    name = "tags",
+                    name = "tag",
                     value = "Describes the tags associated with the enrolment",
                     required = false)
-            @QueryParam("tags")
+            @QueryParam("tag")
                     List<String> tags,
             @ApiParam(
                     name = "offset",

components/device-mgt/io.entgra.device.mgt.core.device.mgt.api/src/main/java/io/entgra/device/mgt/core/device/mgt/api/jaxrs/service/impl/DeviceManagementServiceImpl.java

@@ -151,7 +151,7 @@ public class DeviceManagementServiceImpl implements DeviceManagementService {
             @QueryParam("since") String since,
             @HeaderParam("If-Modified-Since") String ifModifiedSince,
             @QueryParam("requireDeviceInfo") boolean requireDeviceInfo,
-            @QueryParam("tags") List<String> tags,
+            @QueryParam("tag") List<String> tags,
             @QueryParam("offset") int offset,
             @QueryParam("limit") int limit) {
         try {

components/device-mgt/io.entgra.device.mgt.core.device.mgt.api/src/main/java/io/entgra/device/mgt/core/device/mgt/api/jaxrs/service/impl/TagManagementServiceImpl.java

@@ -126,7 +126,7 @@ public class TagManagementServiceImpl implements TagManagementService {
                 log.debug(msg, e);
             }
             return Response.status(Response.Status.BAD_REQUEST).entity(new ErrorResponse.ErrorResponseBuilder().
-                    setMessage(msg).build()).build();
+                    setMessage(e.getMessage()).build()).build();
         }
     }
 

components/device-mgt/io.entgra.device.mgt.core.device.mgt.core/src/main/java/io/entgra/device/mgt/core/device/mgt/core/service/TagManagementProviderServiceImpl.java

@@ -166,13 +166,20 @@ public class TagManagementProviderServiceImpl implements TagManagementProviderSe
         try {
             DeviceManagementDAOFactory.beginTransaction();
             int tenantId = CarbonContext.getThreadLocalCarbonContext().getTenantId();
-            Tag existingTag = tagDAO.getTagById(tag.getId(), tenantId);
-            if (existingTag == null) {
+            Tag tagWithName = tagDAO.getTagByName(tag.getName(), tenantId);
+            if (tagWithName != null && tagWithName.getId() != tag.getId()) {
+                String msg = "Tag with name: " + tag.getName() + " already exists.";
+                log.error(msg);
+                throw new BadRequestException(msg);
+            }
+            if (tagWithName == null || tagWithName.getId() == tag.getId()) {
+                tagDAO.updateTag(tag, tenantId);
+                DeviceManagementDAOFactory.commitTransaction();
+            } else {
                 String msg = "Tag with ID: " + tag.getId() + " does not exist.";
                 log.error(msg);
                 throw new TagNotFoundException(msg);
             }
-            tagDAO.updateTag(tag, tenantId);
             DeviceManagementDAOFactory.commitTransaction();
         } catch (TagManagementDAOException | TransactionManagementException e) {
             DeviceManagementDAOFactory.rollbackTransaction();

components/device-mgt/io.entgra.device.mgt.core.device.mgt.core/src/test/java/io/entgra/device/mgt/core/device/mgt/core/common/TestDataHolder.java

@@ -41,8 +41,8 @@ public class TestDataHolder {
 
     public final static String TEST_DEVICE_TYPE = "TEST-DEVICE-TYPE";
     public final static Integer SUPER_TENANT_ID = -1234;
-    public final static Integer ALTERNATE_TENANT_ID = -1235;
-    public final static Integer ALTERNATE_TENANT_ID_1 = -1236;
+    public final static Integer ALTERNATE_TENANT_ID = 1234;
+    public final static Integer ALTERNATE_TENANT_ID_1 = 1235;
     public final static String SUPER_TENANT_DOMAIN = "carbon.super";
     public final static String initialDeviceIdentifier = "12345";
     public final static String initialDeviceName = "TEST-DEVICE";