尝试抓取facebook pic时令牌为空

Question

我使用scribe从facebook获取oauth令牌并在restfb中传递令牌。我成功地实现了这一目标。我能够检索关于我的信息，例如姓名，电子邮件和身份证。但是当我尝试检索照片时，我没有成功。我发现当我尝试使用print语句（调试目的）时它返回null，因为我无法检索有关照片的任何信息。是令牌的问题，因为我在尝试保存到mongodb时得到一个空指针。我也试过打印令牌但是null？需要一些帮助。

以下是我的代码：

@Controller
public class HomeController {


private static final String STATE = "state";
private String client_id = "***************";
private String app_secret = "**********************";
private String url = "http://localhost:8080";
private ObjectMapper objectMapper;
private OAuthService oAuthService;
private FacebookClient facebookClient;

@Autowired
UserAccountService userAccountService;
@Autowired
UserPhotoService userPhotoService;


public HomeController() {
     this.oAuthService = buildOAuthService(client_id, app_secret);
}
//starts the oauth by passing necessary parameters and initializes oauthservice.
private OAuthService buildOAuthService(String client_id, String app_secret){
    return new ServiceBuilder()
            .apiKey(client_id)
            .apiSecret(app_secret)
            .callback(url+"/auth/facebook/callback") //redirects the callback and must match the url in facebook settings.
            .provider(FacebookApi.class)
            .scope("email")
            .build();
}
  //login page redirects to facebook to get user details
  @RequestMapping(value="/")
  public String HomePage() {
   return "login";
  }

//link redirects to facebook for access token.
@RequestMapping(value="/auth/facebook", method=RequestMethod.GET)
public RedirectView startAuthentication(HttpSession httpSession) throws OAuthException {
    String state = UUID.randomUUID().toString();
    httpSession.setAttribute(STATE, state);
    String authorizationUrl = oAuthService.getAuthorizationUrl(Token.empty())+"&"+STATE+"="+state;
    return new RedirectView(authorizationUrl);
}
//method handles the callback from facebook
@RequestMapping(value="/auth/facebook/callback")
public String callback(@RequestParam("code")String code, @RequestParam(STATE)String state, HttpSession httpsession) throws IOException
{
    //checks state parameter.
    String stateFromSession = (String)httpsession.getAttribute(STATE);
    httpsession.removeAttribute(STATE);
    if(!state.equals(stateFromSession)) { //incase of failure redirects user to login
        return "login";
    }
    //Exchanges the access token
    Token accessToken = getAccessToken(code);
   //pass token to restfb
   this.facebookClient = new DefaultFacebookClient(accessToken.getToken(), Version.VERSION_2_2);
    return "logged"; //successfully logged in.
}

//retrieves the access token
private Token getAccessToken(String code) {
    Verifier verify = new Verifier(code);
    return oAuthService.getAccessToken(Token.empty(), verify);//Token.Empty() method in scribe and handles OAuthservice for both OAuth1 and 2.
}

@RequestMapping(value="/{user-id}/attending", method = RequestMethod.GET)
@ResponseStatus(HttpStatus.OK)
public @ResponseBody void getProfile(@PathVariable("user-id")String userId) {
    User me = facebookClient.fetchObject("me", User.class);
   userAccountService.create(me);//able to retrieve user info successfully
   userPhotoService.create(me, facebookClient); // i pass the token

    return;
}

下面的课程是检索照片的服务：

@Repository
public class UserPhotoServiceImpl implements UserPhotoService {

@Autowired
private PhotoRepo photorepo; //extends mongorepository

public UserPhotos create(User me, FacebookClient faceboookClient){
    UserPhotos userPhotos = new UserPhotos();
    Connection<Photo> photoConnection = facebookClient.fetchConnection("me/photos", Photo.class);
    for(List<Photo> eachPhoto: photoConnection) {
        for(Photo p: eachPhoto){
            userPhotos.setPhotoId(p.getId());//storing info in userPhotos class
            userPhotos.setCountry(p.getPlace().getLocation().getCountry());
        }
    }
    System.out.println(userPhotos.getCountry());//for debugging purposes returns null and cannot retrieve any photos.
   photorepo.save(userPhotos); //trying to save to mongoDB but returns null.

    return userPhotos;
   }
} //

以下是我的UserPhotoService类：

public interface UserPhotoService {
UserPhotos create(User me, FacebookClient facebookClient);
}

似乎令牌返回null或不是相同的令牌。拜托，我需要一些关于错误的帮助。