Facebook login in Google Cloud Endpoints

Question

Can someone explain steps to implement login process with other OAuth2 providers This link Google Cloud Endpoints with another oAuth2 provider gives little info about writin

Answer 1

You need to implement Facebook's client side APIs according to their documentation and the environment you are deploying your client app to (Browser vs iOS vs Android). This includes registering your app with them. Your registered app will direct the user to go through an authentication flow and at the end of it your client app will have access to a short-lived access token. Facebook has multiple types of access tokens, but the one it sounds like you're interested in is called a User Access Token since it identifies an authorized user.

Pass the access token to your Cloud Endpoints API via a field or header. Inside of your API code receive the access token and implement Facebook's API that checks the validity of the access token. The first answer on this SO question makes it look rather easy, but you probably want to reference their documentation again. If that check passes then you would run your API code, otherwise throw an exception.

You will typically also want to implement a caching mechanism to prevent calling the Facebook server side validation API for each Cloud Endpoints request.

Finally, I mentioned that your client app has a short lived token. If you have a client app that is browser-based then you will probably want to upgrade that to a long lived token. Facebook has a flow for that as well which involves your API code requesting a long lived token with the short lived one. You would then need to transfer that long lived token back to the client app to use for future Cloud Endpoints API calls.

If your client app is iOS or Android based then your tokens are managed by Facebook code and you simply request access tokens from the respective APIs when you need them.