java 後臺文件下載

public static void download(HttpServletRequest request, HttpServletResponse response,
			String filePath, String displayName) throws IOException {
		File file = new File(filePath);

		if (StringUtils.isBlank(displayName)) {
			displayName = file.getName();
		}

		if (!file.exists() || !file.canRead()) {
			response.setContentType("text/html;charset=utf-8");
			response.getWriter().write("您下載的文件不存在!");
			return;
		}

		String userAgent = request.getHeader("User-Agent");
		boolean isIE = (userAgent != null) && (userAgent.toLowerCase().indexOf("msie") != -1);

		response.reset();
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "must-revalidate, no-transform");
		response.setDateHeader("Expires", 0L);

		response.setContentType("application/x-msdownload;charset=UTF-8");
		response.setContentLength((int) file.length());

		if (isIE) {
			displayName = URLEncoder.encode(displayName, "UTF-8");
			response.setHeader("Content-Disposition", "attachment;filename=\"" + displayName + "\"");
		} else {
			displayName = new String(displayName.getBytes("UTF-8"), "ISO8859-1");
			response.setHeader("Content-Disposition", "attachment;filename=" + displayName);
		}
		BufferedInputStream is = null;
		OutputStream os = null;
		try {
			os = new BufferedOutputStream(response.getOutputStream());
			is = new BufferedInputStream(new FileInputStream(file));
			FileCopyUtils.copy(is, os);
			//IOUtils.copy(is, os);
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			IOUtils.closeQuietly(is);
		}
	}