Spring-MVC + Json遇到的无法返回前端的坑

          由于做项目使用Spring-MVC架构，而Json格式的数据又是返回前端时经常用到的，越是常见的东西往往莫名其妙的出错，后端是这样写的：

@RequestMapping(value ="/application/applicationPublish", method = RequestMethod.POST, produces = "text/html;charset=utf-8")@ResponseBodypublic Json applicationPublish(@RequestParam("AppImg") MultipartFile AppImg,@RequestParam("AppDoc") MultipartFile AppDoc, DeveloperApplication developerApplication,HttpServletRequest request, HttpServletResponse response) {SessionInfo sessionInfo = (SessionInfo) Webutil.getSessionInfoAttribute(request);//应用发布之前重设协议名称developPackageService.saveNewProtocolName(sessionInfo, developerApplication.getId());Json json = applicationService.savePublishApplication(sessionInfo, AppImg, AppDoc, developerApplication.getId(), developerApplication);return Json;}

            没想到报错了，先是后台报Could not find acceptable representation，把produses去掉以后，前台又报Unexpected token < in JSON at position 0，最后查看http协议头终于解决问题：

普通的form提交后，请求头是这样的：

Accept:

application/json, text/javascript, */*; q=0.01

Content-Type:

application/x-www-form-urlencoded; charset=UTF-8

但是带文件上传的form中，请求头是这样的：

Accept:

text/html,application/xhtml+xml,application/xml;q=0.9,i

Content-Type:

multipart/form-data; boundary=----WebKitFormBounda

其中，Accept代表发送端（客户端）希望接受的数据类型。 Content-Type代表客户端希望接受的数据类型是xml类型。这说明，文件上传的form,客户端希望接收的是text/html类型，而不是Json对象,所以直接返回是有问题的。

  解决上述问题：

@RequestMapping(value ="/application/applicationPublish", method = RequestMethod.POST, produces = "text/html;charset=utf-8")@ResponseBodypublic void applicationPublish(@RequestParam("AppImg") MultipartFile AppImg,@RequestParam("AppDoc") MultipartFile AppDoc, DeveloperApplication developerApplication,HttpServletRequest request, HttpServletResponse response) {SessionInfo sessionInfo = (SessionInfo) Webutil.getSessionInfoAttribute(request);//应用发布之前重设协议名称developPackageService.saveNewProtocolName(sessionInfo, developerApplication.getId());Json json = applicationService.savePublishApplication(sessionInfo, AppImg, AppDoc, developerApplication.getId(), developerApplication);BaseResult.writeJson(request, response, json);}

其实就是把Json对象转化成Json字符串再传到前端即可解决。