Java-HttpUrlConnection

Question

您好，我已经开始使用 HttpUrlConnection，我有一个关于 Http 请求实际发送时间的问题。

我在某处读到，调用 getInputStream() 时会发送实际请求。不过，我已经编写了一些测试代码来处理 POST 请求:

在此版本中，我在 getInputStream() 之前调用 getResponseCode()

URL obj = new URL(myUrl);
HttpURLConnection httpclient = (HttpURLConnection) obj.openConnection();
httpclient.setRequestMethod("POST");
**int responseCode = httpclient.getResponseCode();** 
    try { 
        inStream = httpclient.getInputStream(); 
    }
    catch (IOException ie) { 
        inStream = httpclient.getErrorStream(); 
    }
System.out.println("response code = " + responseCode);

我收到响应代码 200。所以这让我想到请求不是在 getInputStream() 处发送的，而是在较早的方法处发送的。有人对此有任何见解吗？

谢谢!

Answer 1

HttpURLConnection#getResponseCode() 的代码洞察 - openJDK 7

public int getResponseCode() throws IOException {
454        /*
455         * We're got the response code already
456         */
457        if (responseCode != -1) {
458            return responseCode;
459        }
460
461        /*
462         * Ensure that we have connected to the server. Record
463         * exception as we need to re-throw it if there isn't
464         * a status line.
465         */
466        Exception exc = null;
467        try {
468            getInputStream();
469        } catch (Exception e) {
470            exc = e;
471        }
472        ...

基本上，响应代码在初始化时将为-1，这意味着我们没有收到任何响应代码。因此它将建立一个连接URL#getInputStream()并获取响应代码。