Change try catch positions and add error messages to required positions

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

@@ -3606,9 +3606,8 @@ public class DeviceManagementProviderServiceImpl implements DeviceManagementProv
             throws DeviceManagementException {
         List<String> deviceIdentifiers;
 
-        try {
+        if (deviceType == null || StringUtils.isBlank(deviceTypeName)) {
-            if (deviceType == null || deviceTypeName == null || deviceTypeName.isEmpty()) {
+            String msg = "Error, device type cannot be null or empty or a blank space";
-                String msg = "Error, device type cannot be null or empty";
             log.error(msg);
             return false;
         }
@@ -3623,20 +3622,29 @@ public class DeviceManagementProviderServiceImpl implements DeviceManagementProv
             // delete devices
             deviceIdentifiers = devices.stream()
                     .map(Device::getDeviceIdentifier).collect(Collectors.toList());
-                deleteDevices(deviceIdentifiers);
+            try {
+                if(!deleteDevices(deviceIdentifiers)){
+                    log.error("Failed to delete devices of device type: " + deviceTypeName);
+                    return false;
+                }
+            } catch (InvalidDeviceException e) {
+                String msg = "Error occurred while deleting devices of type: " + deviceTypeName;
+                log.error(msg);
+                throw new DeviceManagementException(msg, e);
             }
+        }
+
         // remove device type versions
-            if (!deleteDeviceTypeVersions(deviceType)){
+        if (!deleteDeviceTypeVersions(deviceType)) {
+            log.error("Failed to delete device type vesions for device type: " + deviceTypeName);
             return false;
         }
+
+        try {
             // delete device type
             DeviceManagementDAOFactory.beginTransaction();
             deviceTypeDAO.deleteDeviceType(getTenantId(), deviceType.getId());
             DeviceManagementDAOFactory.commitTransaction();
-        } catch (InvalidDeviceException e) {
-            String msg = "Error occurred while deleting devices of type: " + deviceTypeName;
-            log.error(msg);
-            throw new DeviceManagementException(msg, e);
         } catch (DeviceManagementDAOException e) {
             DeviceManagementDAOFactory.rollbackTransaction();
             String msg = "Error occurred while deleting device type of: " + deviceTypeName;