Objectify - scavenging sessions

My original HttpSessionListener code:

public class SessionListener implements HttpSessionListener {
  @Override
  public void sessionDestroyed(HttpSessionEvent event) {
    final Object user = event.getSession().getAttribute("user");
    if (user != null && user insteaceof User) {
      UserUtils.deleteUser((User) user);
    }
  }
}

and my web.xml

<filter>
  <filter-name>ObjectifyFilter</filter-name>
  <filter-class>com.googlecode.objectify.ObjectifyFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>ObjectifyFilter</filter-name>
  <url-pattern>/*</url-pattern>
</filter-mapping>

When a session timeout event happens it throws:

WARNING: Problem scavenging sessions java.lang.IllegalStateException: You have not started an Objectify context. You are probably missing the ObjectifyFilter. If you are not running in the context of an http request, see the ObjectifyService.run() method. at com.googlecode.objectify.ObjectifyService.ofy(ObjectifyService.java:44) at com.learnkeeper.server.OfyService.ofy(OfyService.java:61) at com.learnkeeper.server.UserUtils.deleteUser(UserUtils.java:28) at com.learnkeeper.server.SessionListener.sessionDestroyed(SessionListener.java:36) at org.mortbay.jetty.servlet.AbstractSessionManager.removeSession(AbstractSessionManager.java:669) at org.mortbay.jetty.servlet.AbstractSessionManager$Session.timeout(AbstractSessionManager.java:926) at org.mortbay.jetty.servlet.HashSessionManager.scavenge(HashSessionManager.java:285) at org.mortbay.jetty.servlet.HashSessionManager.access$000(HashSessionManager.java:44) at org.mortbay.jetty.servlet.HashSessionManager$2.run(HashSessionManager.java:219) at java.util.TimerThread.mainLoop(Timer.java:555) at java.util.TimerThread.run(Timer.java:505)

I tried that (from this post How to resolve "You have not started an Objectify context" in JUnit?):

public class SessionListener implements HttpSessionListener {
  private Closeable closeable;
  @Override
  public void sessionDestroyed(HttpSessionEvent event) {
    final Object user = event.getSession().getAttribute("user");
    if (user != null && user instanceof User) {
      closeable = OfyService.begin();
      UserUtils.deleteUser((User) user);
      closeable.close();
    }
  }
}

And here is my OfyService class:

class OfyService {
  static {
    // Register all my Entities classes
    ObjectifyService.register(User.class);
    ...
  }

  public static Closeable begin() {
    return ObjectifyService.begin();
  }

  public static ObjectifyFactory factory() {
    return ObjectifyService.factory();
  }

  public static Objectify ofy() {
    return ObjectifyService.ofy();
  }
}

but same stacktrace :(

So what did I miss? thx

EDIT

to follow-up with @stickfigure

So I cleaned my project and re-run my use case and I get this stacktrace now:

WARNING: Problem scavenging sessions java.lang.NullPointerException: No API environment is registered for this thread. at com.google.appengine.api.datastore.DatastoreApiHelper.getCurrentAppId(DatastoreApiHelper.java:132) at com.google.appengine.api.datastore.DatastoreApiHelper.getCurrentAppIdNamespace(DatastoreApiHelper.java:148) at com.google.appengine.api.datastore.Key.(Key.java:96) at com.google.appengine.api.datastore.Key.(Key.java:78) at com.google.appengine.api.datastore.KeyFactory.createKey(KeyFactory.java:54) at com.google.appengine.api.datastore.KeyFactory.createKey(KeyFactory.java:47) at com.googlecode.objectify.util.DatastoreUtils.createKey(DatastoreUtils.java:86) at com.googlecode.objectify.impl.KeyMetadata.getRawKey(KeyMetadata.java:187) at com.googlecode.objectify.impl.Keys.rawKeyOf(Keys.java:36) at com.googlecode.objectify.impl.Keys.keyOf(Keys.java:29) at com.googlecode.objectify.impl.LoaderImpl.entity(LoaderImpl.java:121) at com.learnkeeper.server.UserUtils.deleteUser(UserUtils.java:28) at com.learnkeeper.server.SessionListener.sessionDestroyed(SessionListener.java:40) at org.mortbay.jetty.servlet.AbstractSessionManager.removeSession(AbstractSessionManager.java:669) at org.mortbay.jetty.servlet.AbstractSessionManager$Session.timeout(AbstractSessionManager.java:926) at org.mortbay.jetty.servlet.HashSessionManager.scavenge(HashSessionManager.java:285) at org.mortbay.jetty.servlet.HashSessionManager.access$000(HashSessionManager.java:44) at org.mortbay.jetty.servlet.HashSessionManager$2.run(HashSessionManager.java:219) at java.util.TimerThread.mainLoop(Timer.java:555) at java.util.TimerThread.run(Timer.java:505)

Google App Engine Doesn't support session listeners. Session listeners may get invoke in local, but No API environment is registered for this thread. In production listeners will not even invoke.

Source @Ramesh V https://stackoverflow.com/a/11152125/421563

Anyway thx @stickfigure