请问老师4-13我的程序走到Shop shop=null,后边shop就是null了，try完了就停了，不往下走了
@RequestMapping(value = “/regitershop”,method = RequestMethod.POST)
@ResponseBody
private Map<String,Object>registersShop(HttpServletRequest request) {
Map<String ,Object>modleMap=new HashMap<>();

    if (!CodeUtil.changeVerifyCode(request)){
        modleMap.put("success",false);
        modleMap.put("errMsg","验证码错误");
        return modleMap;
    }
    //接收并转化相应的参数，包括店铺信息以及图片信息
   String shopStr= HttpServletRequstUtil.getString(request,"shopStr");
    ObjectMapper objectMapper=new ObjectMapper();
    Shop shop;
    try{
        shop=objectMapper.readValue(shopStr,Shop.class);
    }catch (Exception e){
        modleMap.put("success",false);
        modleMap.put("errMsg",e.getMessage());
        return modleMap;
    }
    CommonsMultipartFile shopImg;
    CommonsMultipartResolver commonsMultipartResolver=new CommonsMultipartResolver(
            request.getSession().getServletContext()
    );
    if (commonsMultipartResolver.isMultipart(request)){
        MultipartHttpServletRequest multipartHttpServletRequest= (MultipartHttpServletRequest) request;
        shopImg= (CommonsMultipartFile) multipartHttpServletRequest.getFile("shopImg");
    }else{
        modleMap.put("success",false);
        modleMap.put("errMsg","上传图片不能为空");
        return modleMap;
    }