[EDIT] This method is meant to be used only by server side applications, in general it’s not a good practice to include the app_id and app_secret in an API call!
Since I started using the Facebook Graph API, the Access Token generation has always been by biggest problem: they are not easy to generate, and they expire!
So you need to make calls to the Facebook Graph API from a Facebook APP and you don’t want to use a user generated token? There is an easy way!
There is an alternative method to call the Facebook Graph API that doesn’t require a user generated token:
https://graph.facebook.com/endpoint?key=value&access_token=app_id|app_secret
And… That’s it!! Just give to your app the right permissions, and you’ll never need to generate an Access Token again!!