@Override
 public List<Application> getApplicationListForDevice(DeviceIdentifier deviceId)
     throws ApplicationManagementException {
   Device device;
   try {
     int tenantId = CarbonContext.getThreadLocalCarbonContext().getTenantId();
     DeviceManagementDAOFactory.openConnection();
     device = deviceDAO.getDevice(deviceId, tenantId);
     if (device == null) {
       if (log.isDebugEnabled()) {
         log.debug(
             "No device is found upon the device identifier '"
                 + deviceId.getId()
                 + "' and type '"
                 + deviceId.getType()
                 + "'. Therefore returning null");
       }
       return null;
     }
     return applicationDAO.getInstalledApplications(device.getId());
   } catch (DeviceManagementDAOException e) {
     throw new ApplicationManagementException(
         "Error occurred while fetching the Application List of '"
             + deviceId.getType()
             + "' device carrying the identifier'"
             + deviceId.getId(),
         e);
   } catch (SQLException e) {
     throw new ApplicationManagementException(
         "Error occurred while opening a connection to the data source", e);
   } finally {
     DeviceManagementDAOFactory.closeConnection();
   }
 }
  @Override
  public Activity installApplicationForUsers(Operation operation, List<String> userNameList)
      throws ApplicationManagementException {

    String userName = null;
    try {
      List<Device> deviceList;
      List<DeviceIdentifier> deviceIdentifierList = new ArrayList<>();
      DeviceIdentifier deviceIdentifier;

      for (String user : userNameList) {
        userName = user;
        deviceList =
            DeviceManagementDataHolder.getInstance()
                .getDeviceManagementProvider()
                .getDevicesOfUser(user);
        for (Device device : deviceList) {
          deviceIdentifier = new DeviceIdentifier();
          deviceIdentifier.setId(Integer.toString(device.getId()));
          deviceIdentifier.setType(device.getType());

          deviceIdentifierList.add(deviceIdentifier);
        }
      }
      // TODO: Fix this properly later adding device type to be passed in when the task manage
      // executes "addOperations()"
      String type = null;
      if (deviceIdentifierList.size() > 0) {
        type = deviceIdentifierList.get(0).getType();
      }

      return DeviceManagementDataHolder.getInstance()
          .getDeviceManagementProvider()
          .addOperation(type, operation, deviceIdentifierList);
    } catch (InvalidDeviceException e) {
      throw new ApplicationManagementException("Invalid DeviceIdentifiers found.", e);
    } catch (DeviceManagementException e) {
      throw new ApplicationManagementException(
          "Error in get devices for user: " + userName + " in app installation", e);

    } catch (OperationManagementException e) {
      throw new ApplicationManagementException("Error in add operation at app installation", e);
    }
  }
  @Override
  public void updateApplicationListInstalledInDevice(
      DeviceIdentifier deviceIdentifier, List<Application> applications)
      throws ApplicationManagementException {
    List<Application> installedAppList = getApplicationListForDevice(deviceIdentifier);
    try {
      int tenantId = CarbonContext.getThreadLocalCarbonContext().getTenantId();
      DeviceManagementDAOFactory.beginTransaction();
      Device device = deviceDAO.getDevice(deviceIdentifier, tenantId);

      if (log.isDebugEnabled()) {
        log.debug("Device:" + device.getId() + ":identifier:" + deviceIdentifier.getId());
      }

      if (log.isDebugEnabled()) {
        log.debug("num of apps installed:" + installedAppList.size());
      }
      List<Application> appsToAdd = new ArrayList<>();
      List<Integer> appIdsToRemove = new ArrayList<>(installedAppList.size());

      for (Application installedApp : installedAppList) {
        if (!applications.contains(installedApp)) {
          if (log.isDebugEnabled()) {
            log.debug("Remove app Id:" + installedApp.getId());
          }
          appIdsToRemove.add(installedApp.getId());
        }
      }
      applicationMappingDAO.removeApplicationMapping(device.getId(), appIdsToRemove, tenantId);
      Application installedApp;
      List<Integer> applicationIds = new ArrayList<>();

      for (Application application : applications) {
        if (!installedAppList.contains(application)) {
          installedApp =
              applicationDAO.getApplication(
                  application.getApplicationIdentifier(), application.getVersion(), tenantId);
          if (installedApp == null) {
            appsToAdd.add(application);
          } else {
            applicationIds.add(installedApp.getId());
          }
        }
      }
      if (log.isDebugEnabled()) {
        log.debug("num of apps add:" + appsToAdd.size());
      }
      applicationIds.addAll(applicationDAO.addApplications(appsToAdd, tenantId));

      if (log.isDebugEnabled()) {
        log.debug("num of app Ids:" + applicationIds.size());
      }
      applicationMappingDAO.addApplicationMappings(device.getId(), applicationIds, tenantId);

      if (log.isDebugEnabled()) {
        log.debug("num of remove app Ids:" + appIdsToRemove.size());
      }

      DeviceManagementDAOFactory.commitTransaction();
    } catch (DeviceManagementDAOException e) {
      DeviceManagementDAOFactory.rollbackTransaction();
      throw new ApplicationManagementException(
          "Error occurred saving application list to the device", e);
    } catch (TransactionManagementException e) {
      throw new ApplicationManagementException("Error occurred while initializing transaction", e);
    } finally {
      DeviceManagementDAOFactory.closeConnection();
    }
  }