OOAuthException: An active access token must be used to query information about the current user

I am using restfb java sdk for adding facebook login in my app
i have already created a test app but when i try to get the detail of the user following error message displayed

[FacebookOAuthException: Received Facebook error response of type OAuthException: An active access token must be used to query information about the current user. (code 2500, subcode null)]

here is my code

val config = ConfigFactory.load()  
    val FBAppId = config.getString("fb.app.id")
      val FBAppSecret = config.getString("fb.app.secretkey")
      val aceessToken = new DefaultFacebookClient().obtainAppAccessToken(FBAppId, FBAppSecret)
    log.info("token is "+aceessToken.getAccessToken)
    val facebookClient = new DefaultFacebookClient(aceessToken.getAccessToken)
    val fbuser = facebookClient.fetchObject("me",classOf[User] ,Parameter.`with`("fields", "id,name,email, first_name , last_name"))
    log.info("name : {} ", fbuser.getName)
    log.info("User first  name :{} ", fbuser.getFirstName)
    log.info("User last name : {}" , fbuser.getLastName)
    log.info("User Email : {}" , fbuser.getEmail)

here is the access token printed on console

 token is 587299244766256|udH5HgYve1DHGjKHU55hBw9Ik5Y

(i think this in not correct as i have read in Facebook docs that access token consists of 150 characters and the token that is generating is not 150 character long ) and in this line

val fbuser = facebookClient.fetchObject("me",classOf[User] ,Parameter.`with`("fields", "id,name,email, first_name , last_name"))

the exception thrown

[FacebookOAuthException: Received Facebook error response of type OAuthException: An active access token must be used to query information about the current user. (code 2500, subcode null)]

please help me how can i get the details of logged in users

You cannot fetch the endpoint me with an app access token. You need a user or page access token.