java web 文件下载

File file = new File(fileName);
			InputStream fis = new BufferedInputStream(new FileInputStream(fileName));
			byte[] buffer = new byte[fis.available()];
			fis.read(buffer);
			fis.close();
			// 清空response
			response.reset();
			BufferedInputStream br = new BufferedInputStream(new FileInputStream(file));
			byte[] buf = new byte[1024];
			int len = 0;
			// 纯下载方式
			response.setHeader("Content-Disposition", "attachment; filename=" + dis.getTitle()+".zip");
			OutputStream out = response.getOutputStream();
			while ((len = br.read(buf)) > 0){
				out.write(buf, 0, len);
			}
			br.close();
			out.close();