Send a post login from java code and get cookie authentication

Question

I need to login to an IIS web-server.

After login, I need to send an HTTP Post with a lot of data.

However, I don't know how to save my cookies from login and reuse them for subsequent HTTP calls.

My code

private final static Logger logger = Logger.getLogger(HttpURLConnectionExample.class);

private static final String CERTIFICATE_CLIENT = "/src/main/resources/clientcert.jks";
private static final String JAVAX_NET_SSL_KEY_STORE_PASSWORD = "javax.net.ssl.keyStorePassword";
private static final String JAVAX_NET_SSL_KEY_STORE = "javax.net.ssl.keyStore";
private static PropertiesManagement management;
private static final String LOGIN_PAGE = "https://alloggiatiweb.poliziadistato.it/Alloggiatiweb/Login.aspx";
private static final String COOKIES_HEADER = "Set-Cookie";
private static CookieManager msCookieManager = new CookieManager();
private static final String INTERNAL_PAGE = "https://alloggiatiweb.poliziadistato.it/Alloggiatiweb/Analisi.aspx";
private HttpsURLConnection conn;

private static void setCertificateSSL() throws FileNotFoundException, KeyStoreException, IOException, NoSuchAlgorithmException, CertificateException {
    FileInputStream fin = new FileInputStream(management.getFilePath());
    KeyStore ks = KeyStore.getInstance(management.getSSLProtocol());
    ks.load(fin, management.getPassword().toCharArray());
    System.setProperty(JAVAX_NET_SSL_KEY_STORE, CERTIFICATE_CLIENT);
    System.setProperty(JAVAX_NET_SSL_KEY_STORE_PASSWORD, management.getPassword());
}

public static void main(String[] args) throws Exception {
    management = new PropertiesManagement();
    setCertificateSSL();
    HttpURLConnectionExample http = new HttpURLConnectionExample();
    http.login();
}

private void getInternalPage() throws Exception {
    URL obj = new URL(INTERNAL_PAGE);
    conn = (HttpsURLConnection) obj.openConnection();
    conn.setReadTimeout(10000);
    conn.setConnectTimeout(15000);
    conn.setRequestMethod("GET");
    conn.setDoInput(true);
    conn.connect();
    logger.info("[GET ON " + obj + " RESPONSE CODE-MESSAGE]" + conn.getResponseCode() + " - " + conn.getResponseMessage());
    BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();
    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();
    logger.info(response.toString());
}

private void login() throws Exception {
    URL obj = new URL(LOGIN_PAGE);
    conn = (HttpsURLConnection) obj.openConnection();
    conn.setReadTimeout(10000);
    conn.setConnectTimeout(15000);
    conn.setRequestMethod("POST");
    conn.setDoOutput(true);
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("txtUtente", management.getUsername()));
    params.add(new BasicNameValuePair("txtPwd", management.getPassword()));

    OutputStream os = conn.getOutputStream();
    BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
    writer.write(getQuery(params));
    writer.flush();
    writer.close();
    os.close();
    conn.connect();
    Map<String, List<String>> headerFields = conn.getHeaderFields();
    List<String> cookiesHeader = headerFields.get(COOKIES_HEADER);
    if (cookiesHeader != null) {
        for (String cookie : cookiesHeader) {
            msCookieManager.getCookieStore().add(null, HttpCookie.parse(cookie).get(0));
        }
    }
    logger.info("[POST ON " + obj + " RESPONSE CODE-MESSAGE]" + conn.getResponseCode() + " - " + conn.getResponseMessage());
    getInternalPage();
    conn.disconnect();
}

private String getQuery(List<NameValuePair> params) throws UnsupportedEncodingException {
    StringBuilder result = new StringBuilder();
    boolean first = true;
    for (NameValuePair pair : params) {
        if (first)
            first = false;
        else
            result.append("&");
        result.append(URLEncoder.encode(pair.getName(), "UTF-8"));
        result.append("=");
        result.append(URLEncoder.encode(pair.getValue(), "UTF-8"));
    }
    return result.toString();
}

and this is response

 INFO (HttpURLConnectionExample.java:125) [19 apr 2016 15:08:51,013] - [POST ON https://alloggiatiweb.poliziadistato.it/Alloggiatiweb/Login.aspx RESPONSE CODE-MESSAGE]200 - OK
 INFO (HttpURLConnectionExample.java:83) [19 apr 2016 15:08:51,461] - [GET ON https://alloggiatiweb.poliziadistato.it/Alloggiatiweb/Analisi.aspx RESPONSE CODE-MESSAGE]200 - OK
 INFO (HttpURLConnectionExample.java:94) [19 apr 2016 15:08:51,464] - <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transit
.....

but the page print aren't internal page but it's login page