我使用 AJAX 请求从控制器获取结果，以将其填充到数据表中。结果以 JSON 格式从控制器返回，但我一直收到 Uncaught TypeError: Cannot read property 'length' of undefined 错误。

我是否应该在控制器中设置其他数据表参数？

控制器类：

    @RequestMapping(value = "/users/list", method = RequestMethod.GET, produces = "application/json")
    @ResponseBody
    public List<User> listOfUsers() {
    List<User> usersList;
    usersList = userService.getAllUsers();
    return usersList;
}

thymeleaf 中的数据表 UI：

           <div class="table-responsive">
                    <table id="usersTable" class="table table-bordered table-hover dataTable">
                        <thead>
                        <tr>
                            <th th:text="#{user.table.heading.username}">User Name</th>
                            <th th:text="#{systemUser.table.heading.firstname}">First Name</th>
                            <th th:text="#{systemUser.table.heading.lastname}">Last Name</th>
                            <th th:text="#{systemUser.table.heading.status}">Status</th>
                            <th th:text="#{systemUser.table.heading.role}">Role</th>
                        </tr>
                        </thead>
                    </table>
                </div>

AJAX 请求：

<script th:inline="javascript">
$(document).ready(function () {
    $('#usersTable').DataTable({
        "processing": true,
        dataType: 'json',
        "ajax": {
            "url": "http://localhost:8080/sample/users/list",
            "type": "GET"
        },
        "columns": [
            {"data": "username"},
            {"data": "firstName"},
            {"data": "lastName"},
            {"data": "status"},
            {"data": "roleName"}
        ]
    })
});
</script>

JSON 响应：

[  
 {  
  "id":1,
  "username":"[email protected]",
  "firstName":dinesh,
  "lastName":damian,
  "password":"$2a$10dfgfdgfdgd6O.iO6XB5xcyEZuppAHWOZGwX8m8xCLqS",
  "status":"ACTIVE",
  "role":{  
     "id":1,
     "roleName":"ADMIN",
     "status":"ACTIVE",
     "permissionList":[  
        {  
           "id":1,
           "name":"ROLE_LOGIN",
           "description":"User login permission",
           "checked":false
        }
     ],
     "checkedPermissions":[  

     ]
  }

} ]