**文件写入流**
/* FileInputStream inputStream = new FileInputStream(f);
//通过response获取ServletOutputStream对象(out)
ServletOutputStream out = response.getOutputStream();;
int b = 0;
byte[] buffer = new byte[1024];
while ((b = inputStream.read(buffer))!= -1) {
//写到输出流(out)中
out.write(buffer, 0, b);
}
inputStream.close();
out.close();
out.flush();*/