Question

I am using Google App Engine, spring mvc and spring jpa dao. In my application i want to delete an entry from the database when session is destroyed. So i am using session listeners which actually wants to deletes an entry from the database through spring dao bean.

Here is my code in session listener

@Override
public void sessionDestroyed(HttpSessionEvent se) {
//get entry from session and now remove entry from database
getMyDao(se).delete(entry);
}

private MyDao getMyDao(HttpSessionEvent sessionEvent){

     HttpSession session = sessionEvent.getSession();

    ApplicationContext ctx = 
          WebApplicationContextUtils.
                getWebApplicationContext(session.getServletContext());

    MyDao dao = 
                (MyDao) ctx.getBean("myDao");

    return dao;
}

I am getting the below error when i try deleting

java.lang.NullPointerException: No API environment is registered for this thread.
at com.google.appengine.api.datastore.DatastoreApiHelper.getCurrentAppId(DatastoreApiHelper.java:108)
at com.google.appengine.api.datastore.DatastoreApiHelper.getCurrentAppIdNamespace(DatastoreApiHelper.java:118)
at com.google.appengine.api.datastore.Query.(Query.java:112)
at org.datanucleus.store.appengine.query.DatastoreQuery.validate(DatastoreQuery.java:794)
at org.datanucleus.store.appengine.query.DatastoreQuery.performExecute(DatastoreQuery.java:225)
at org.datanucleus.store.appengine.query.JPQLQuery.performExecute(JPQLQuery.java:80)

Can any one please tell me why api environment is not registered when i invoke from session listener?

Answer 1

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.