Hi,

I have a problem where I get the following messages at times, I get the following messages:
* session is closed
* illegal attempt to assiciate a collection to two open sessions.

I wonder id this is a problem in my design or whether it occurs b/c of debugging mode. I also use Sitemesh.

I have no closeSession statements in the dao-layer and I use a HibernateFilter to close the session at the end of the request (open session in view pattern). A lot of the information I need to render in the view are collections of the user object, which is stored in the http session. Therefore I reassociate it with every request.

Hibernate version: 2.1.7

HibernateFilter.java:

public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;

//reattach user object to Hibernate session to prevent lazy
// initialization errors
Object user0 = request.getSession().getAttribute("user");
User user = null;
if (user0 != null) {
user = (User) user0;
try {
Session session = HibernateUtil.getSession();
HibernateUtil.beginTransaction();
session.lock(user, LockMode.NONE);
HibernateUtil.commit();
} catch (HibernateException he) {
logger.error(he);
}
}

try {

chain.doFilter(req, res);

} catch (ServletException e) {

logger.error("error handling filter chain: HibernateFilter "
, e);
throw e;

} catch (IOException io) {
logger.error("error handling filter chain: HibernateFilter "
, io);
throw io;
} finally {
try {
HibernateUtil.closeSession();
} catch (HibernateException he) {
logger.error(he);
throw new ServletException(he);
}
}

}



HibernateUtil.java

private static final SessionFactory sessionFactory;
private static final ThreadLocal threadSession = new ThreadLocal();
private static final ThreadLocal threadTransaction = new ThreadLocal();

static {
try {
// Create the SessionFactory
sessionFactory = new Configuration().configure().buildSessionFactory();

} catch (Throwable ex) {
logger.error("Initial SessionFactory creation failed.", ex);
throw new ExceptionInInitializerError(ex);
}
}

public static void init(){}

public static Session getSession(){
Session s = (Session) threadSession.get();
try {
if(s == null){
s = sessionFactory.openSession();
threadSession.set(s);
}
if(!s.isOpen()){
s = sessionFactory.openSession();
}
} catch (HibernateException he) {
logger.error(he);
}
return s;
}

public static void closeSession() throws HibernateException{
try{
Session s = (Session) threadSession.get();
threadSession.set(null);
if(s != null && s.isOpen())s.close();
}catch(HibernateException e){
logger.error(e);
throw new HibernateException(e);
}
}



Thanks,

Marc

This is not thread safe code, try to synchronize filter or make http session "light weight".

I read on the hibernate site:
When to create and when to close a session depending on your framework (struts, spring, etc). First I was opening the session for each request call inside the Struts actions, but the session would close prematurely by the time the JSP is executed. Then I tried a Servlet Listener pattern as prescribed in the book Hibernate in Action (Christian Bauer, Gavin King - Manning). That would cause trouble as well because the session would remain open and Tiles insert would cause multiple session to open before others were closed.
My last resort was to extend Struts Actions servlet and wrap the processRequest() with the open/close call for the session and that seems to be very stable. (http://www.hibernate.org/113.html)

This seems to suggest that the hibernatefilter basically is not workable in many frameworks. Sitemesh and Tiles are pretty common. I'm a little surprised that such a crucial aspect of implementing Hibernate is clouded in uncertainty. To tell you the truth, I'm totally confused now, but I can't believe it could be this difficult. So, it must be me :-)

Can anybody enlighten me on the definitive way to use the open session in view in a layered application using sitemesh or tiles? Let's assume that objects will have lazy collection references and that those collections will be accessed in the jsp as well.

Thanks,

Marc