int s = context.getRealPath("/").lastIndexOf("web_upload");
String downloadpath = context.getRealPath("/").substring(0, s)
+"ptop"+File.separator+"xiazai" + File.separator;
System.out.println(downloadpath);
或者
int s = context.getRealPath("").lastIndexOf("\\");//获取上一级目录
String downloadpath = context.getRealPath("").substring(0, s)+File.separator
+"ptop"+File.separator+"xiazai" + File.separator;
下载
<a href="../web_upload/servlet/down?downFile=2.rar">下载</a>