OAuth is a protocol that allows a user to grant a third party limited permission to access a web application on her behalf, without sharing her credentials (username and password) with the third party. The third party can be a web application, or any other application with the capability of invoking a web browser for the user, such as a desktop application or an app running on a smart phone. In the terms of the OAuth specification, the application seeking permission is the consumer, and the application providing the data is the service provider.
Note: OAuth support in App Engine has been released as an experimental feature. The API may change in future minor releases of the App Engine runtime environment. Please try it out, and let us know what you think!
This reference describes how to use OAuth with Java applications as the service provider. It has the following sections: