问题：
在HbuilderX中使用mui.ajax()函数访问后台数据时，发现出现：

Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource

解决：
在后台Controller类上加入：

@CrossOrigin(origins = "*", maxAge = 3600)

如：

@CrossOrigin(origins = "*", maxAge = 3600)
public class UserController {