Spring Jackson序列化对象列表并不像预期的那样工作

Question

我必须序列化用户列表。

这是我的控制器方法声明

@RequestMapping(value = "/users", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public @ResponseBody List<UserDTO> getUsersData(Authentication authentication) {
      // .... 
      // get users from the service layer as an ArrayList
      List<UserDTO> users = userService.getUsers(authentication.getName());
      return users;
}

在客户端，我得到了这个JSON：

{"ArrayList":[
    {"id":8,"firstName":"User1 FN","lastName":"User1 LN"},
    {"id":9,"firstName":"User2 FN","lastName":"User2 LN"}
]}

我希望收到：

{[
    {"id":8,"firstName":"User1 FN","lastName":"User1 LN"},
    {"id":9,"firstName":"User2 FN","lastName":"User2 LN"}
]}

我在这里想念的是什么？！