springMVC中使用spring的form標(biāo)簽庫(kù)，edit.jsp代碼如下：jspFullname:Username:Nospaces,Please.Password:6charactersormore.EmailAddress:Incaseyouforgetsomething.Sendmeemailupdates!控制器的代碼如下：java@RequestMapping(method=RequestMethod.GET,params="new")publicStringcreateSpitterProfile(Modelmodel){model.addAttribute(newSpitter());return"spitters/edit";}@RequestMapping(method=RequestMethod.POST)publicStringaddSpitterFromForm(@Valid@ModelAttribute("spitter")Spitterspitter,BindingResultbindingResult){if(bindingResult.hasErrors()){return"spitters/edit";}spitterService.saveSpitter(spitter);return"redirect:/spitter/"+spitter.getName();}在jsp的語(yǔ)句中，如果enctype=application/x-www-form-urlencoded則運(yùn)行正常；如果調(diào)成multipart/form-data后，提交表單時(shí)不管用戶名寫(xiě)的是什么，轉(zhuǎn)到的網(wǎng)頁(yè)后面顯示的用戶名都是null。請(qǐng)問(wèn)這是怎么回事？