Android身份验证：如何在谷歌应用引擎中存储/访问用户凭据？

Question

我正在为我的Android应用创建一个登录系统。我想跟随     发生：

1. User enters username/password.
2. Login button sends request to custom API in google app engine.
3. App engine performs a check in google cloud sql if the user entered correct credentials or not.
4. If user entered correct credentials then response comes as a valid access token and user logs in successfully.

我无法找到实现上述目标的方法。我是API和登录系统的新手。我需要知道如何创建一个可以读取请求的api并进行检查并返回结果。