In the end I got it working with HSql but once I switched to PostgreSQL
I could only get the JDBC transaction factory working.  Possibly due to
some obscure service errors JBoss now kicks out on startup.

Judging from other replies there is *of course* a better way to do
this.  That is one of my frustrations - every time I make some progress
I find another article that indicates there is a better way.

There were some excellent sections in the Hibernate in action book, I
especially liked the architecture tips.  Now it is dated as I am using
EJB 3.0 with JBoss 4.0.4 (which incidently appears to ******* rock.
Coupled with Hibernate and all the other technologies you can do some
serious enterprise apps in a small about of time.

Anyway here is my suboptimal postgresql transaction setup

JBoss 4.0.4
EJB 3.0 Java 1.5.0.7
Hibernate3.jar that shipped with it 5/15/2006

public static void store(IBaseModel model, boolean continueSession)
throws Exception {
try {
if (model.getId() == null) {
HibernateUtil.getSession().save(model);
} else {
IBaseModel original = (IBaseModel)
load(model.getClass(),model.getId(),true);
model.copyModifiedTo(original);
HibernateUtil.getSession().save(original);
}
if (!continueSession) {
HibernateUtil.endSession();
}
} catch (Exception e) {
Log.warn(model);
HibernateUtil.rollbackSession();
throw e;
}
}

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import com.myproject.framework.logging.Log;

public class HibernateUtil {

private static Session currentSession = null;
private static SessionFactory sessionFactory = null;
private static Transaction transaction = null;

/**
* Configure the sessionFactory from hibernate.cfg.xml
*/
static {
try {
Configuration configuration = new Configuration().configure();
sessionFactory = configuration.buildSessionFactory();
} catch (Throwable ex) {
ex.printStackTrace(System.out);
ex.printStackTrace(System.err);
Log.fatal(ex);
System.exit(1);
}
}

/**
* Return the sessionFactory from cache
*
* @return
* @throws Exception
*/
private static SessionFactory getSessionFactory() throws Exception {
if (sessionFactory == null) {
throw new NullPointerException();
} else {
return sessionFactory;
}
}

/**
* Return the current session if it exists otherwise
* open a new session and start a new transaction
*
* @return
* @throws Exception
*/
public static Session getSession() throws Exception {
if (currentSession == null) {
currentSession = getSessionFactory().openSession();
if (currentSession == null) {
throw new NullPointerException();
}
transaction = currentSession.beginTransaction();
}
return currentSession;
}

/**
* Commit the transaction, rollback on error and close the session
*
* @throws Exception
*/
public static void endSession() throws Exception {
Session session = null;
try {
session = getSession();
transaction.commit();
} catch (Exception ex) {
Log.error(ex);
transaction.rollback();
} finally {
try {
session.close();
} catch (Exception ex2) {
Log.error(ex2);
} finally {
cleanup();
}
}
}

/**
* Remove the session and transaction from cache
*/
private static void cleanup() {
transaction = null;
currentSession = null;
}

/**
* Rollback the transaction and close the session
*
* @throws Exception
*/
public static void rollbackSession() {
try {
if (transaction != null) {
transaction.rollback();
}
} finally {
try {
Session session = getSession();
if (session != null) {
session.close();
}
} catch (Exception ex2) {
Log.error(ex2);
} finally {
cleanup();
}
}
}

}

package com.myproject.model.common;

public interface IBaseModel {

/**
* Unique database identifier
*
* @return
*/
public Long getId();

/**
* Copy all modified fields to the target model
*
* @param model
*/
public void copyModifiedTo(IBaseModel model);

}

hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory>
<property name="current_session_context_class">thread</property>
<property
name="hibernate.connection.driver_class">org.postgresql.Driver</property>

<property
name="hibernate.connection.url">jdbc:postgresql://localhost:5432/postgres</property>

<property name="hibernate.connection.username">myproject</property>
<property name="hibernate.connection.password">myproject</property>
<property
name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
<property name="show_sql">true</property>
<property
name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>

<property name="hibernate.cache.provider_class">
org.hibernate.cache.HashtableCacheProvider
</property>
<property name="hibernate.hbm2ddl.auto">create-drop</property>
<property
name="hibernate.transaction.manager_lookup_class">org.hibernate.transaction.JBossTransactionManagerLookup</property>

<property name="jta.UserTransaction">UserTransaction</property>

<mapping
resource="com/myproject/model/patient/PatientModel.hbm.xml"/><mapping
resource="com/myproject/model/common/AddressModel.hbm.xml" />

</session-factory>

</hibernate-configuration>