关于文件上传的坑，tomcat一重启图片就消失

 <Context path ="/File" docBase ="D:/File" debug ="0" privileged ="true">
        </Context>

String productName = req.getParameter("productName");
        String productDesc = req.getParameter("productDesc");
        String productPrice = req.getParameter("productPrice");
        Part cover = req.getPart("productImage");
        Long da = new Date().getTime()/1000;
        String filePath = "/"+da+"_"+cover.getSubmittedFileName();
        File file = new File("/File"); //这里是重点
        String destPath = file.getAbsolutePath()+filePath;
        new File(destPath).getParentFile().mkdir();
        cover.write(destPath);
        int categoryId = Integer.parseInt(req.getParameter("categoryId"));
        Product product = new Product(productName,productDesc,new BigDecimal(productPrice),filePath,categoryId);
        ProductService service = new ProductService();
        service.insertProduct(product);
        resp.sendRedirect(req.getContextPath()+"/index");