java实现文件的下载

系统日志的获取不可能每次都登录服务器，所以在页面上能够下载系统运行的日志是必须的

如何来实现日志的下载，这样的一个功能

 前端我们用到的是window.open(...)这样可以发送一个get请求到后台

 后台接收到get请求之后，如何实现对文件的下载

	@ResponseBody
	@RequestMapping("downlogsfile")
	public void downlogsfile(HttpServletResponse response,String filename) throws IOException {
		logger.info("**************下载日志相关的日志信息{}*****************",filename);
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/plain;charset=GBK");
		String path =configService.getByConfigValueByName("LOGPATH");
		String filepath = path + "/" + filename;
		logger.info(filepath);
		File file = new File(filepath);
		if (file.exists()) {
			logger.info("找到相关的日志文件：{}", filepath);
			DownLoadUtils.downloadtxt(response, file);
		} else {
			logger.info("文件不存在");
		}
	}

关键是DownLoadUtils.downloadtxt(response, file);

	public static void downloadtxt(HttpServletResponse res,File file) throws IOException {
		long length = file.length();
		res.addHeader("Content-Length", String.valueOf(length));
		res.addHeader("Content-Type","text/plain; charset=utf-8");
		res.setHeader("Content-Disposition","attachment;filename="+file.getName());
		OutputStream outputStream = res.getOutputStream();
		byte[] buff = new byte[1024];
		BufferedInputStream bis = null;
		FileInputStream fileInputStream=new FileInputStream(file);
		bis = new BufferedInputStream(fileInputStream);
		int i = bis.read(buff);
		while (i != -1) {
			outputStream.write(buff, 0, buff.length);
			outputStream.flush();
			i = bis.read(buff);
		}
		bis.close();
		fileInputStream.close();
		outputStream.close();
	}

这个里面res.setHeader很重要

res.addHeader("Content-Type","text/plain; charset=utf-8");

text/plain  纯文本的格式，并且设置编码
res.setHeader("Content-Disposition","attachment;filename="+file.getName());

"Content-Disposition","attachment;filename="+file.getName()

实现下载