Java 带有POST数据的Android HttpsUrlConnection在姜饼上不起作用

我已经编写了从外部服务器下载一些数据的代码。服务器正在使用自签名证书，需要设置会话cookie和一些POST数据。目前我有以下代码：

private byte[] getResponse(URL url, String postData) 
    throws IOException, KeyManagementException, CertificateException, KeyStoreException, 
    NoSuchAlgorithmException
{
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    HttpsURLConnection urlConnection = (HttpsURLConnection) url.openConnection();
    urlConnection.setRequestProperty("User-Agent", userAgent);
    urlConnection.setRequestProperty("Cookie", cookie);
    urlConnection.setRequestMethod("POST");
    urlConnection.setDoInput(true);
    urlConnection.setDoOutput(true);

    urlConnection.setSSLSocketFactory(getSocketFactory());

    OutputStream os = urlConnection.getOutputStream();
    BufferedWriter writer = new BufferedWriter(
            new OutputStreamWriter(os, "UTF-8"));
    writer.write(postData);
    writer.flush();
    writer.close();
    os.close();

    try {
        urlConnection.connect();
        InputStream is = urlConnection.getInputStream();
        int len = 0;
        while ((len = is.read(buffer)) != -1) 
        {
            baos.write(buffer, 0, len);
        }

    }
    catch(IOException e)
    {
        throw e;
    }
    finally {
        urlConnection.disconnect();
    }
    return baos.toByteArray();
}

在冰激凌三明治和更高的（API>=14）上，一切正常。当我试图使应用程序在API>=8上工作时，问题就开始了。它现在正确地发送带有GET和no-params（CAPTCHA）的请求，但是当涉及到获取实际数据时，urlConnection的connect方法毫无例外地失败。getSocketFactory（）的代码是：

---

编辑：我刚刚意识到connect方法显然是有效的，但它没有遵循响应的重定向，所以输入流总是空的。

我自己刚刚找到了它。由于某种原因，HttpsUrlConnection似乎并不遵循API 10及更低版本上的重定向，即使隐式调用setInstanceFlowRedirects（true）。它只是忽略了这个设置。在调用urlConnection.connect（）之后，我用这段代码解决了这个问题：

private SSLSocketFactory getSocketFactory() 
    throws CertificateException, IOException, KeyStoreException, NoSuchAlgorithmException, 
    KeyManagementException
{
    CertificateFactory cf = CertificateFactory.getInstance("X.509");
    InputStream caInput = context.getResources().openRawResource(R.raw.historiapojazdu);
    Certificate ca;
    try {
    ca = cf.generateCertificate(caInput);
    } finally {
    caInput.close();
    }
    // Create a KeyStore containing our trusted CAs
    String keyStoreType = KeyStore.getDefaultType();
    KeyStore keyStore = KeyStore.getInstance(keyStoreType);
    keyStore.load(null, null);
    keyStore.setCertificateEntry("ca", ca);

    // Create a TrustManager that trusts the CAs in our KeyStore
    String tmfAlgorithm = TrustManagerFactory.getDefaultAlgorithm();
    TrustManagerFactory tmf = TrustManagerFactory.getInstance(tmfAlgorithm);
    tmf.init(keyStore);

    // Create an SSLContext that uses our TrustManager
    SSLContext context = SSLContext.getInstance("TLS");
    context.init(null, tmf.getTrustManagers(), null);

    return context.getSocketFactory();
}

String redirect = urlConnection.getHeaderField("Location");
        if(redirect != null)    //truth before ICS
        {
            urlConnection.disconnect();

            urlConnection = (HttpsURLConnection) (new URL(redirect)).openConnection();
            urlConnection.setRequestProperty("User-Agent", userAgent);
            urlConnection.setRequestProperty("Cookie", cookie);
            urlConnection.setRequestMethod("POST");
            urlConnection.setDoInput(true);
            urlConnection.setDoOutput(true);

            urlConnection.setSSLSocketFactory(getSocketFactory());

            OutputStream os2 = urlConnection.getOutputStream();
            BufferedWriter writer2 = new BufferedWriter(
                    new OutputStreamWriter(os2, "UTF-8"));
            writer2.write(postData);
            writer2.flush();
            writer2.close();
            os2.close();

            urlConnection.connect();
        }