ClientLoginUtil.java

import java.io.*;
import java.net.*;
import java.util.*;
import java.util.logging.*;

public class ClientLoginUtil {
  static final Logger logger = Logger.getLogger(ClientLoginUtil.class.getName());
  static final String CLIENTLOGIN_URL = "https://www.google.com/accounts/ClientLogin";

  /**
   * @param email
   * @param password
   * @param applicationName
   *            {yourname}-{applicationName}-{versionNumber}
   * @param applicationUrl url of your application
   *            e.g. {@literal http://shin1ogawa.appspot.com/}
   * @param continueUrl url of needs authenticate
   *         e.g. {@literal http://shin1ogawa.appspot.com/pathToNeedsAuthenticate}
   * @return cookie value {@literal ACSID=....} for http or {@literal SACSID=....} for https
   * @throws IOException
   */
  public static String getCookie(String email, String password,
      String applicationName, String applicationUrl, String continueUrl) throws IOException {
    String authToken = getAuthTokenUsingGoogleClientLogin(email, password, applicationName);
    return getCookieUsingAppengineLogin(applicationUrl, continueUrl, authToken);
  }

  static String getAuthTokenUsingGoogleClientLogin(String email,
      String password, String applicationName) throws IOException {
    URL url = new URL(CLIENTLOGIN_URL);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
    PrintWriter w = new PrintWriter(new OutputStreamWriter(connection.getOutputStream()));
    w.print("Email=" + URLEncoder.encode(email, "utf-8"));
    w.print("&Passwd=" + URLEncoder.encode(password, "utf-8"));
    w.print("&service=" + URLEncoder.encode("ah", "utf-8"));
    w.print("&source=" + URLEncoder.encode(applicationName, "utf-8"));
    w.print("&accountType=" + URLEncoder.encode("HOSTED_OR_GOOGLE", "utf-8"));
    w.flush();
    w.close();
    connection.connect();

    BufferedReader reader = new BufferedReader(new InputStreamReader(
        connection.getInputStream()));
    String line = null;
    while ((line = reader.readLine()) != null) {
      if (line == null || line.startsWith("Auth") == false) {
        continue;
      }
      return line.substring(line.indexOf('=') + 1);
    }
    throw new AssertionError();
  }

  static String getCookieUsingAppengineLogin(String applicationUrl,
      String continueUrl, String authToken) throws IOException {
    StringBuilder _url = new StringBuilder(applicationUrl)
        .append(applicationUrl.endsWith("/") ? "" : "/")
        .append("_ah/login?").append("continue=")
        .append(URLEncoder.encode(continueUrl, "utf-8")).append("&")
        .append("auth=").append(URLEncoder.encode(authToken, "utf-8"));
    if (logger.isLoggable(Level.FINE)) {
      logger.log(Level.FINE, "GET " + _url);
    }
    URL url = new URL(_url.toString());
    boolean followRedirects = HttpURLConnection.getFollowRedirects();
    HttpURLConnection.setFollowRedirects(false);
    try {
      HttpURLConnection connection = (HttpURLConnection) url.openConnection();
      connection.setRequestProperty("X-appcfg-api-version", "dummy");
      connection.connect();

      if (logger.isLoggable(Level.FINE)) {
        logger.log(Level.FINE, "responseCode=" + connection.getResponseCode());
      }
      Map<String, List<String>> headers = connection.getHeaderFields();
      Iterator<Map.Entry<String, List<String>>> i = headers.entrySet().iterator();
      while (i.hasNext()) {
        Map.Entry<String, List<String>> next = i.next();
        String key = next.getKey();
        if (key == null || key.equals("Set-Cookie") == false) {
          continue;
        }
        List<String> values = next.getValue();
        if (values.isEmpty() == false) {
          return values.get(0);
        } else {
          return null;
        }
      }
      return null;
    } finally {
      HttpURLConnection.setFollowRedirects(followRedirects);
    }
  }
}