CommonsMultipartFile转File

场景：

 CommonsMultipartFile shopImg = null;
        CommonsMultipartResolver commonsMultipartResolver =
                new CommonsMultipartResolver(request.getSession().getServletContext());
        if (commonsMultipartResolver.isMultipart(request)) {
            MultipartHttpServletRequest multipartHttpServletRequest = (MultipartHttpServletRequest) request;
            //从请求中分离出图片文件，形成的是CommonsMultipartFile类型文件
            shopImg = (CommonsMultipartFile) multipartHttpServletRequest.getFile("shopImg");
        } 

//生成一个特定文件夹下的的随机文件名文件，用来转换
 File shopImgFile = new File(PathUtil.getImgBasePath() + ImageUtil.getRandomFileName());
            try {
                shopImgFile.createNewFile();
            } catch (IOException e) {
                modelMap.put("success", false);
                modelMap.put("error Message:", "shopImgFile 创建失败 : " + e.getMessage() );
                return modelMap;
            }
            try {
           		 //在这里使用
                inputStreamToFile(shopImg.getInputStream(), shopImgFile);
            } catch (IOException e) {
                modelMap.put("success", false);
                modelMap.put("error Message:", "inputStreamToFile 执行失败 :" + e.getMessage());
                return modelMap;
            }
            //在shopService.addShop的方法中，第二个参数是File类型
            ShopExecution shopExecution =  shopService.addShop(shop, shopImgFile);

  private static void inputStreamToFile(InputStream ins, File file) {
        FileOutputStream outputStream = null;

        try {
            outputStream = new FileOutputStream(file);
            int bytesRead = 0;
            byte[] buffer = new byte[1024];
            while ((bytesRead = ins.read(buffer)) != 1) {
                outputStream.write(buffer, 0, bytesRead);
            }

        } catch (Exception e) {
            throw new RuntimeException("调用inputStreamToFile产生异常：" + e.getMessage());
        } finally {
            try {
                if (outputStream != null) {
                    outputStream.close();
                }

                if (ins != null) {
                    ins.close();
                }
            } catch (Exception e) {
                throw new RuntimeException("关闭inputStreamToFile产生异常：" + e.getMessage());
            }
        }

    }

使用inputStreamToFile这个方法就可以实现转换了（原理是因为CommonsMultipartFile类型有一个getInputStream()方法），可以获得文件流然后转换成File类型。