I want OpenID on GAE/J. I don't want yet another +100kB JAR. Am I lost?

Question

Usually people ask for 'best library', but I assume OpenID authentication is only a couple of requests in/out...? And I'm on GAE where more JARs means slower cold-start. For example openid4java-0.9.5.jar has 190kB. That seems like an insanely high cost for some URL reading and text parsing.

Am I missing something? Is it more complicated then what is needed when requesting access_token and user info from Facebook?

Is there some well explained howto? (This looks good but seems to be useful only for Google Accounts.)
Or is the authentication that complicated (or identity providers that non-compatible) that I should just accept +190kB and add them to my JARs? (Or maybe wait with OpenID for now.)

Answer 1

Use the Federated login characteristics provided by the Google App Engine. Federated Login refers to any service that allows users to create a single ID or account and use it to authenticate with various services. OpenID is the only Federated Login supported by the Google App Engine Users service.

You can find more information about the Authentication Options here: http://code.google.com/appengine/docs/java/users/overview.html#Authentication_Options

And I would recommend to read the "User Experience summary for Federated Login" also: http://sites.google.com/site/oauthgoog/UXFedLogin/summary