Your question is "The current situation is that if the incoming parameter is not a number, it will be returned 400 Bad Request and you don't know why?"

Still, "You want to automatically return 400 Bad Request when the incoming parameter is not a number"

Added:

Can you change it like this? If you are using spring4:

@RequestMapping("/test")
@ResponseBody
public String test(@RequestParam("id") Long id, BindingResult result){
    if (result.hasErrors()) {
        return "返回你想返回的";
    }
    return id + "";
}

I haven’t written for a long time, it should be ok

Added:

It seems to be specified@Valid之类的注解的，你得仔细查查spring的文档，我实在不确定annotation是不是我写的这个@RequestParam(depending on whether your parameters come from the url or other places)

If you are so confused, just accept itObject id 然后第一行代码判断id instanceof Long Just kidding. .
If what is passed in is not a number, it probably won’t go to your method.