springboot请求报404的问题求助！！！！

@Controller
@RequestMapping("/a")
public class TController {

    @RequestMapping("/test")
    @ResponseBody
    public Map test( Map s) {
        return s;
    }

}

这样写的请求会报404

@Controller
@RequestMapping("/a")
public class TController {

    @RequestMapping("/test")
    @ResponseBody
    public Map test(@RequestParam Map s) {
        return s;
    }

}

这样就没问题，是为什么呢？

https://blog.csdn.net/weixin_40160720/article/details/86601556

声明@RestController替换@Controller