java 根据URL下载文件

 /**
     * 根据地址获得数据的输入流
     *
     * @param strUrl 网络连接地址
     * @return url的输入流
     */
    public static InputStream getInputStreamByUrl(String strUrl) {
        HttpURLConnection conn = null;
        try {
            URL url = new URL(strUrl);
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(20 * 1000);
            final ByteArrayOutputStream output = new ByteArrayOutputStream();
            IOUtils.copy(conn.getInputStream(), output);
            return new ByteArrayInputStream(output.toByteArray());
        } catch (Exception e) {
            logger.error(e + "");
        } finally {
            try {
                if (conn != null) {
                    conn.disconnect();
                }
            } catch (Exception e) {
                logger.error(e + "");
            }
        }
        return null;
    }