问题原因:在 ​​@Valid​​​ 的那个参数后面紧跟着一个 ​​BindingResult​​ 的参数(一定要紧跟着)

正确的参数签名

"publishPost.do")
public String publishPost(@Valid @ModelAttribute Post post,
BindingResult bindingResult,
Errors errors, Model model, Integer tid,String action, RedirectAttributes attributes) {

错误的签名

//发帖
@PostMapping("publishPost.do")
public,Integer tid,
BindingResult bindingResult,
Errors errors, Model model, String action, RedirectAttributes attributes) {