Issue creating Google tag manager service object

[debojit via StackOverflow]

I am using Google Tag Manager API to create tag manager service object but I am getting an error like this "java.lang.NoClassDefFoundError: java.nio.file.Files is a restricted class. Please see the Google App Engine developer's guide for more details".

private static final String CLIENT_SECRET_JSON_RESOURCE  = "client_secrets.json";

private static final File DATA_STORE_DIR = new File("PATH_TO_DIRECTORY");

private static final String APPLICATION_NAME = "walnutdemoapp";
private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();
private static NetHttpTransport httpTransport;
private static FileDataStoreFactory dataStoreFactory;

public static TagManager getTagManager() {
try {
  httpTransport = GoogleNetHttpTransport.newTrustedTransport();
  dataStoreFactory = new FileDataStoreFactory(DATA_STORE_DIR);

  // Authorization flow.
  Credential credential = authorize();
  TagManager manager = new TagManager.Builder(httpTransport, JSON_FACTORY, credential)
      .setApplicationName(APPLICATION_NAME).build();
  return manager;
} catch (Exception e) {
  e.printStackTrace(System.err);
  return null;
}
}

private static Credential authorize() throws Exception {
// Load client secrets.
GoogleClientSecrets clientSecrets = GoogleClientSecrets.load(JSON_FACTORY,
    new InputStreamReader(TagManagerUtil.class.getResourceAsStream(CLIENT_SECRET_JSON_RESOURCE)));

// Set up authorization code flow for all auth scopes.
GoogleAuthorizationCodeFlow flow = new GoogleAuthorizationCodeFlow.Builder(httpTransport,
    JSON_FACTORY, clientSecrets, TagManagerScopes.all()).setDataStoreFactory(dataStoreFactory)
    .build();

// Authorize.
return new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");
}

I am getting the exception while creating the new FileDataStoreFactory which I cannot figure out why.Where do I need to set the user's credential and in what format?Any kind of help would be highly appreciated.The stacktrace goes here.

java.lang.NoClassDefFoundError: java.nio.file.Files is a restricted class. Please see the Google App Engine developer's guide for more details.
at com.google.appengine.runtime.Request.process-2b983165ceac1ba1(Request.java)
at java.nio.file.Files.<clinit>(Files.java)
at java.lang.reflect.Method.invoke(Method.java:44)
at com.google.api.client.util.IOUtils.isSymbolicLink(IOUtils.java:203)
at com.google.api.client.util.store.FileDataStoreFactory.<init>(FileDataStoreFactory.java:59)
at com.adwalnut.api.TagManagerUtil.getTagManager(TagManagerUtil.java:40)
at com.adwalnut.api.CreateContainer.doGet(CreateContainer.java:42)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:446)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:453)
at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:276)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:312)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:304)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:450)
at java.lang.Thread.run(Thread.java:745)

Please DO NOT REPLY directly to this email but go to StackOverflow:
http://stackoverflow.com/questions/39871464/issue-creating-google-tag-manager-service-object

[Eric Burley via StackOverflow]

Use of file APIs on app engine is restricted due to the distributed file system. You should be able to use AppEngineDataStoreFactory instead.

Please DO NOT REPLY directly to this email but go to StackOverflow:

http://stackoverflow.com/questions/39871464/issue-creating-google-tag-manager-service-object/39896797#39896797