HttpURLConnection实现下载功能

private String connectToTerminal(String urlStr) {    LogUtils.i(TAG, "下载 url "+urlStr);    LogUtils.i(TAG, "[jinxiuzhen]connectToTerminal();");       URL url = null;    HttpURLConnection connection = null;    InputStream is = null;    String result = null;    try {        url = new URL(urlStr);        connection = (HttpURLConnection) url.openConnection();        connection.setRequestMethod("GET");        connection.setConnectTimeout(5000);        connection.setRequestProperty("Content-Type", "application/json");        connection.setRequestProperty("X-API-KEY", LoginReceiver.keyToken);        connection.setRequestProperty("url", urlStr);        is = connection.getInputStream();        InputStreamReader isReader = new InputStreamReader(is);        BufferedReader bufferedReader = new BufferedReader(isReader);        String buffer = "";        StringBuilder sb = new StringBuilder();        while ((buffer = bufferedReader.readLine()) != null) {                    sb.append(buffer);        }        result = sb.toString();        LogUtils.i(TAG, "result=》"+result);    } catch (MalformedURLException e) {        e.printStackTrace();    } catch (IOException e) {        e.printStackTrace();    } finally {        if (is != null) {            try {                is.close();            } catch (IOException e) {                e.printStackTrace();            }        }        if (connection != null) {            connection.disconnect();        }    }    return result;}