struts1.x 实现文件下载

public ActionForward download(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		String fileName = request.getParameter("file");
		String rootPath = this.servlet.getServletContext().getRealPath("files");
		File f = new File(rootPath);
		if (!f.exists())
			f.mkdirs(); // 如果文件夹不存在,则创建
		File toFile = new File(rootPath, fileName);
		FileInputStream fis = new FileInputStream(toFile);

		// 初始化response
		response.reset();
		response.setContentType("application/x-msdownload");
		response.setHeader("Content-Disposition", "attachment; filename="
				+ new String(fileName.getBytes(), "ISO-8859-1"));
		OutputStream os = response.getOutputStream();

		byte[] b = new byte[1024];
		int real = fis.read(b);
		while (real > 0) {
			os.write(b, 0, real);
			real = fis.read(b);
		}
		os.close();
		fis.close();
		return null;
	}

以下是action 代码