mustername = java.net.URLEncoder.encode(mustername, "utf-8");
//new String(mustername.getBytes("gbk"), "ISO_8859_1");两种方式都可以
    HttpServletResponse response = ActionContext.getActionContext().getResponse();

    response.setContentType("application/vnd.ms-excel;charset=GBK");
    response.addHeader("Content-Disposition", "attachment;filename=\"" + mustername +".xls" + "\"");