idcs-sdk-sample-apps cannot work

Summary

idcs-sdk-sample-apps cannot work

Content

I'm trying this example for IDCS SDK with Web application.

http://www.oracle.com/webfolder/technetwork/tutorials/obe/cloud/idcs/idcs_java_sdk_obe/idcs-java-sdk.html

Does this example and SDK work fine you expected?  It seems that user information cannot be got from IDCS in the part of CallbackServlet.

//Getting the Access Token Value.

String access_token = ar.getAccessToken();

//The application then creates a User Session.

IDCSUserManager um = new IDCSUserManagerImpl(config);

IDCSUser user = um.getAuthenticatedUser(access_token);   <--- user is returned as null

Access token would be valid because I can get user information by using it with REST API. so I'm not sure what could cause this problem.