下载图片（二进制数据）

         /**
	 * 下载二进制软件
	 * @param urlName
	 * @param dir
	 * @return
	 * @throws IOException
	 */
	public static String downBin(String urlName, String dir) throws IOException {
		URL url = new URL(urlName);
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		conn.connect();
		HttpURLConnection.setFollowRedirects(true);
		byte[] buf = new byte[128];
		BufferedInputStream bis = new BufferedInputStream(conn.getInputStream());
		// 保存文件
		int size = 0;
		FileOutputStream fos = new FileOutputStream(dir);
		while ((size = bis.read(buf)) != -1) {
			fos.write(buf);
		}
		fos.flush();
		fos.close();
		return null;
	}