1.    DiskFileUpload upload = new DiskFileUpload();

       upload.setHeaderEncoding("utf8");

2.jsp文件的request.setCharacterEncoding("UTF-8");

3.      FileItem item = (FileItem) itr.next();

     String value = new String(item.getString().getBytes()) ;

均无效！

最终的解决办法是 使用 org.apache.commons.fileupload组件里的一个方法:

    String value = new String(item.getString("UTF-8")) ;