HttpsURLConnection是否需要connect（）方法？

Question

虽然我在模拟器中运行google android示例代码，但我有一个问题。在不调用connect（）方法的情况下，服务器请求运行良好。它是干什么用的？我已注释掉“ connection.connect（）;”而且它仍然像什么都没有改变一样工作。是否应该显式调用connect（）？

*开发环境：Android Studio + openJDK 1.8 +模拟器

private String downloadUrl(URL url) throws IOException {
            InputStream stream = null;
            HttpsURLConnection connection = null;
            String result = null;
            try {
                connection = (HttpsURLConnection) url.openConnection();
                // Timeout for reading InputStream arbitrarily set to 3000ms.
                connection.setReadTimeout(3000);
                // Timeout for connection.connect() arbitrarily set to 3000ms.
                connection.setConnectTimeout(3000);
                // For this use case, set HTTP method to GET.
                connection.setRequestMethod("GET");
                // Already true by default but setting just in case; needs to be true since this request
                // is carrying an input (response) body.
                connection.setDoInput(true);
                // Open communications link (network traffic occurs here).
//                connection.connect(); <======================================== I have commented out
                publishProgress(DownloadCallback.Progress.CONNECT_SUCCESS);
                int responseCode = connection.getResponseCode();
                if (responseCode != HttpsURLConnection.HTTP_OK) {
                    throw new IOException("HTTP error code: " + responseCode);
                }
                // Retrieve the response body as an InputStream.
                stream = connection.getInputStream();
                publishProgress(DownloadCallback.Progress.GET_INPUT_STREAM_SUCCESS, 0);
                if (stream != null) {
                    // Converts Stream to String with max length of 500.
                    result = readStream(stream, 500);
                    publishProgress(DownloadCallback.Progress.PROCESS_INPUT_STREAM_SUCCESS, 0);
                }
            } finally {
                // Close Stream and disconnect HTTPS connection.
                if (stream != null) {
                    stream.close();
                }
                if (connection != null) {
                    connection.disconnect();
                }
            }
            return result;
        }

Answer 1

A connect()呼叫在那里不是必需的。当您调用getResponseCode()时，这将导致HttpURLConnection建立基础连接，发送请求并等待直到响应到达……如果这些事情尚未发生。

这同时适用于Java SE和Android实现。