文件下载不可用异步方式

response.addHeader("Content-Disposition","attachment;filename="+new String("你好.xls".getBytes("GBK"),"ISO8859-1"));
response.setContentType("application/octet-stream");
OutputStream os = response.getOutputStream();
os.write(by);
os.flush();

os.close();

window.location.href="exportMarketDataServlet?contractNos="+contractNos;