Accessing signed Facebook JSON using Play 2.0.1 and RestFB - facebook-graph-api

Question

I'm writing an Play 2.0.1 application that will be deployed within a canvas page on Facebook. I'm using restFB for the Facebook API.
By manually creating an Access Token at https://developers.facebook.com/tools/explorer?method=GET I can get my application to access the Facebook user's name and render it in the Canvas page iFrame on Facebook.
So, my app controller receives the POST and renders a page like this:
public static Result handle_fb_post() {
return redirect(routes.canvas.fb_render_profile_page());
}
public static Result fb_render_profile_page() {
String accessToken = "<access token copied from facebook graph explorer>";
DefaultFacebookClient().getExtendedAccessToken(application_id, application_secret);
FacebookClient facebookClient = new DefaultFacebookClient(accessToken);
User fbUser = facebookClient.fetchObject("me", com.restfb.types.User.class);
return ok(views.html.fbuser.render(fbUser));
}
My routes are set up as:
POST /fbcanvas/ controllers.FBCanvas.handle_fb_post()
GET /fbcanvas/profile controllers.FBCanvas.fb_render_profile_page()
However, how can I get access to the signed JSON that Facebook sends me in the POST? I believe that this also contains the access token from the user (assuming that they have authorised my app) as described here:
https://developers.facebook.com/docs/samples/canvas/ (See section on "signed_request Parameter").
There are a number of examples out there for Java, PHP, Javascript and Python, but I can't find any that describe how to do this in Play 2 or using RestFB. I have tried a number of different approaches, but cannot work out how to access the signed request in Play 2.
Can anyone help and explain how this can be done?

Answer 1

If the token is sent as Json in the POST request, you can grab it via
def handle_post() = Action { implicit request =>
val jsonBody = request.body.asJson
//process it
}