code: public String remove() {
      Long[] userIds = getLongIds("user");
      User creator = userService.get(SecurityUtils.getUsername());
      List<User> toBeRemoved = securityHelper.getUserService().getUsers(userIds);
      StringBuilder sb = new StringBuilder();
      User removed = null;
      int success = 0;
      int expected = toBeRemoved.size();
      try {
        for (User one : toBeRemoved) {
          removed = one;
          // 不能删除自己
          if (!one.getId().equals(creator.getId())) {
            securityHelper.getUserService().removeUser(creator, one);
            success++;
          } else {
            addFlashError("security.info.cannotRemoveSelf");
            expected--;
          }
        }
      } catch (Exception e) {
        sb.append(',').append(removed.getName());
      }
      if (sb.length() > 0) {
        sb.deleteCharAt(0);
        addFlashMessage("security.info.userRemovePartial", success, sb);
      } else if (expected == success && success > 0) {
        addFlashMessage("info.remove.success");
      }
      return redirect("search");
    }
docs: 删除一个或多个用户