下载url资源

public static void downloadFileFromUrl(String fileUrl, String fileName, String savePath) throws Exception {
        //获取连接
        URL url = new URL(fileUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setConnectTimeout(3 * 1000);
        //设置请求头
        connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.110 Safari/537.36");
        //获取输入流
        InputStream in = connection.getInputStream();

        File saveDir = new File(savePath);
        if (!saveDir.exists()) {
            saveDir.mkdirs();
        }
        File file = new File(savePath, fileName);

        OutputStream out = new FileOutputStream(file);

        byte[] bytes = new byte[1024];
        int len = 0;
        while ((len = in.read(bytes)) != -1) {
            out.write(bytes, 0, len);
        }
        out.close();
        in.close();
    }

　　也可以用Apache common io的工具类