Spring Boot – OAuth 2 – Inject the OAuth2Authentication in the controllers

There are multiple ways of retrieving user/client information associated to the token specified in a request.
With Spring, a very simple way is adding a OAuth2Authentication parameter in the controller of the method we where want to get that information.
In Oauth2, a token is always issued for a client (client in the frame of the oauth2 vocabulary, that is client application) but the token may be associated or not to a user.
With that Spring feature, we could so retrieve these information.
For example by writing a controller method signature such as :

@RequestMapping( method = RequestMethod.GET)
  public ResponseEntity<Foo> get(OAuth2Authentication auth) throws URISyntaxException {<br />    .... <br />}

To get the user authentication object :

  import org.springframework.security.core.Authentication;
  Authentication userAuth = auth.getUserAuthentication();

To get the oauth2 request (associated to the client application) :

  import org.springframework.security.oauth2.provider.OAuth2Request;
  OAuth2Request oauth2Request = auth.getOAuth2Request();