On Sat, 27 Sep 2003, Juozas Baliuka wrote:
> It must be bug in "SessionHolder".
Hi, Juozas. That code below was actuallly incorrect in my last email, and
I have corrected it in-line below: I am actually storing this.ftpSession
instead of this.session (line 71 in the original quoted code below).
As for the SessionHolder object, I'm using that so that I don't have
hundreds of connections to the back-end PostgreSQL database. I've include
the code beow -- it should connect to the database if needed and just
return a connected net.sf.hibernate.Session object from its method.
01:public class SessionHolder
02:{
03: private static final boolean DEBUG = true;
04: private static Session session;
05:
06: public static Session getSession()
07: {
08: SessionHolder.connect();
09:
10: return(SessionHolder.session);
11: }
12:
13: public static void connect()
14: {
15: if (SessionHolder.session == null)
16: {
17: try
18: {
19: SessionFactory sessionFactory = new Configuration()
20: .configure().buildSessionFactory();
21: SessionHolder.session = sessionFactory.openSession();
22: } catch (HibernateException e)
23: {
24: if (SessionHolder.DEBUG) e.printStackTrace();
25: }
26: } else
27: {
28: try
29: {
30: SessionHolder.session.reconnect();
31: } catch (Exception e) {}
32: }
33: }
34:
35: public static void disconnect()
36: {
37: if (SessionHolder.session != null)
38: {
39: try
40: {
41: SessionHolder.session.close();
42: SessionHolder.session.disconnect();
43: } catch (HibernateException e) {}
44: }
45: }
46:}
QHat do you think? Is there a better way that I should be doing this
without rewriting a heck of a lot of code? I like the idea of having the
session establishment self-contained within the SessionHolder object?
Does this SessionHolder seem to be the culprit behind the
ConcurrentModificationException issues?
> > We seem to be having some problems like this in more than one section
> > of code. I really don't understand it at all; we suspect some kind of
> > JVM bug. Unfortunately, no-one has been able to deliver a testcase
> > that will help me reproduce this on my machine.
> > I can't really do much, until I can reproduce it.
> > P.S. You might also get this if you share a session between two
> > threads - but at least some occurrences of this problem do not seem to
> > be caused by this....
> > >I'm receiving an Exception in a Hibernate application I've built, and
> > >I'm a bit confused as to why this might be happening. The code at
> > >where the Exception is thrown is quite simple, and I think this might
> > >be a bug in Hibernate itself. I've searched Google for this to no
> > >avail, and I'm using the latest recommended Hibernate release as
> > >available on the site.
> > >The exception I receive has a stacktrace as follows:
> > > java.util.ConcurrentModificationException
> > > at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
> > > at java.util.AbstractList$Itr.remove(Unknown Source)
> > > at net.sf.hibernate.impl.SessionImpl.executeAll(SessionImpl.java:2101)
> > > at net.sf.hibernate.impl.SessionImpl.execute(SessionImpl.java:2061)
> > > at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2005)
> > > at net.sf.hibernate.transaction.JDBCTransaction.commit(
> > > JDBCTransaction.java:57
> > > )
> > > at
> org.express.ftpsrv.ConnectionHandler.<init>(ConnectionHandler.java:72)
> > > at
> org.express.ftpsrv.ConnectionListener.accept(ConnectionListener.java:56)
> > > at
> org.express.ftpsrv.ConnectionListener.main(ConnectionListener.java:19)
> > >
> > >And the code at ConnectionHandler.java:72 that causes this looks like:
> > >
> > > 52:this.ftpSession = new FtpSession();
> > > 53:
> > > 54:/* ftpSession.setSessionId() does not operate on the unique
> > > 55: * 'id' field that is also part of the ftpSession object.
> > > 56: */
> > > 57:ftpSession.setSessionId(UniqueGenerator.makeUniqueNumber());
> > > 58:
> > > 59:Date currentDate = new Date();
> > > 60:currentDate.setTime(System.currentTimeMillis());
> > > 61:this.ftpSession.setBegTime(currentDate);
> > > 62:
> > > 63:net.sf.hibernate.Session hSession = null;
> > > 64:Transaction transaction = null;
> > > 65:
> > > 66:try
> > > 67:{
> > > 68: hSession = SessionHolder.getSession();
> > > 69:
> > > 70: transaction = hSession.beginTransaction();
> > > 71: hSession.save(this.ftpSession);
> > > 72: transaction.commit();
> > > 73:} catch (HibernateException e)
> > > 74:{
> > > 75: transaction.rollback();
> > > 76:}
> > >I'd like to point out that this seems to be an intermittent thing,
> > >occurring more often when I instantiate many objects quickly (the
> > >quoted lines 52-72, above, are within a cronstructor in the Object).
> > >Does anyone have any ideas as to what might be happening or where I
> > >might look for additional information in order to track down this
> > >bug? Thanks, in advance, for any response on this.
-- _
__ __ ___ _| | William R. Lorenz <[EMAIL PROTECTED]>
\ V V / '_| | http://www.clevelandlug.net/ ; "Every revolution was
\./\./|_| |_| first a thought in one man's mind." - Ralph Waldo Emerson
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