Using app access token had previously been asked in this question (How to use Facebook appAccessToken with Spring Social) and Craig Walls gave a good explanatio
You do not need to fetch an app access token - you can actually use the app id and secret separated by "|" as the access token. - You can see it at the bottom of the app access token section in the documentation: https://developers.facebook.com/docs/facebook-login/access-tokens#apptokens