Spring-boot demo for facebook oauth login. Reference by facebook manually-build-a-login-flow.
The REST resource of /api/facebook/user/login will be generate a facebook oauth login url,
you can pass with perms parameter, perms means facebook login permissions, can ref facebook permissions,
curl -XGET "http://localhost:8888/api/facebook/user/login?perms=public_profile,email,friends"when client click the oauth login url, facebook will send a request to /api/facebook/oauth/callback,
you must be setting Valid OAuth redirect URIs on your facebook app dashboard.

The REST resource of /api/facebook/oauth/callback will handle the facebook callback,
You must implement verify state parameter to defend dangerous request.
then pass code parameter to request facebook user's access_token, ref by Exchanging Code for an Access Token
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