关于commonsMultipartResolver

CommonsMultipartFile shopImg = null;
CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver(request.getSession().getServletContext());

if(commonsMultipartResolver.isMultipart(request)){}

老师你好，这一块我不太明白。上面先是request.getSession().getServletContext()得到commonsMultipartResolver对象，下面又if(commonsMultipartResolver.isMultipart(request))进行判断，我觉得多此一举了吧，如果 如果request不存在，那commonsMultipartResolver也不会存在了，因为之前new CommonsMultipartResolver的时候就用到了request.