spring mvc 多文件上传时报错MultipartHttpServletRequest

1、确认<form name="contractForm" id="contractForm" action="" method="post" enctype ="multipart/form-data">；
　　2、确认commons-fileupload.jar 和 org.springframework.web.jar 存在环境
　　3、MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest)request；
　　这一句会报错：ApplicationHttpRequest cannot be cast to MultipartHttpServletRequest
　　解决办法是通过这种方式：
　　MultipartResolver resolver = new CommonsMultipartResolver(request.getSession().getServletContext());
　　MultipartHttpServletRequest multipartRequest = resolver.resolveMultipart(request);