MultipartHttpServletRequest multiRequest = (MultipartHttpServletRequest) request;类型转换异常问题

	String root = request.getParameter("root");
		// 先实例化一个文件解析器
        CommonsMultipartResolver coMultipartResolver = new CommonsMultipartResolver(request.getSession()
                .getServletContext());

        // 判断request请求中是否有文件上传
        if (coMultipartResolver.isMultipart(request)) {
            // 转换request
            MultipartHttpServletRequest multiRequest = (MultipartHttpServletRequest) request;
            // 获得文件
            MultipartFile file = multiRequest.getFile("Filedata");
            if(!file.isEmpty()){
            	resourceMng.saveFile(root, file);
            }
        }
		request.setAttribute("root", root);
		
		ResponseUtils.renderText(response, "");
		return null;
	}

上传文件时，

MultipartHttpServletRequest multiRequest = (MultipartHttpServletRequest) request;

报错类型转换异常，原来是需要在Spring的配置文件进行如下配置：

<!-- 专题上传文件 -->
	<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">  
     <property name="maxUploadSize" value="104857600"/>  
       <property name="maxInMemorySize" value="4096"/>  
    </bean>