IdentifierGenerator gen = new HiLoGenerator();

IdentifierGenerator gen = new TableHiLoGenerator();

public void configure(Type type, Properties params, Dialect d)

public class TableHiLoGenerator extends TableGenerator {
   
   /**
    * The max_lo parameter
    */
   public static final String MAX_LO = "max_lo";
   
   private long hi;
   private int lo;
   private int maxLo;
   private Class returnClass;
   
   private static final Log log = LogFactory.getLog(TableHiLoGenerator.class);
   
   public void configure(Type type, Properties params, Dialect d) {
      super.configure(type, params, d);
      maxLo = PropertiesHelper.getInt(MAX_LO, params, Short.MAX_VALUE);
      lo = maxLo + 1; // so we "clock over" on the first invocation
      returnClass = type.getReturnedClass();
   }

TableHiLoGenerator.java:

/// Start of snippet

   public synchronized Serializable generate(SessionImplementor session, Object object)
      throws SQLException, HibernateException {
         
      // This has to be done using a different connection to the
      // containing transaction because the new hi value must
      // remain valid even if the containing transaction rolls
      // back
      Connection conn  = session.getFactory().openConnection();

/// End of snippet


public class HiLoGeneratorBean extends SessionBeanBase
{
   private SessionFactory sessionFactory;

   // Use the built-in Hibernate hi/lo generator:
   TableHiLoGenerator gen = new TableHiLoGenerator();
   
   public HiLoGeneratorBean()
   {
      Dialect dialect = new net.sf.hibernate.dialect.MySQLDialect();
      Properties props = new Properties();
      props.setProperty("hibernate.connection.autocommit", "false");
      gen.configure(Hibernate.LONG, props, dialect);
   }

   /**
    * @ejb.interface-method
    * @ejb.facade-method
    */
   public Long next() throws HibernateException
   {
      try
      {
         Session session = getSession();
         if (session instanceof SessionImplementor)
         {
            Long nextID = null;
            boolean toggleAutoCommit = session.connection().getAutoCommit();
            if (toggleAutoCommit) session.connection().setAutoCommit(false);
            try
            {
               nextID = (Long) gen.generate((SessionImplementor) session, null);
            }
            finally
            {
               if (toggleAutoCommit) session.connection().setAutoCommit(true);
               session.close();
            }
            return nextID;
         }
         else
         {
            throw new HibernateException("getSession() did not deliver a SessionImplementor");
         }
      }
      catch (SQLException sqle)
      {
         throw new HibernateException(sqle);
      }
   }

   private SessionFactory getSessionFactory() throws HibernateException
   {
      if (sessionFactory == null)
      {
         sessionFactory = new Configuration().configure().buildSessionFactory();
      }

      return sessionFactory;
   }

   private Session getSession() throws HibernateException
   {
      return getSessionFactory().openSession();
   }
}

<hibernate-configuration>
    <!-- a SessionFactory instance listed as /jndi/name -->
    <session-factory name="java:comp/env/hibernate/PilotusAdminFactory">
        <!-- properties -->
        <property name="hibernate.connection.datasource">java:/PilotusAdminDS</property>
        <property name="hibernate.dialect">net.sf.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.show_sql">true</property>
        <property name="hibernate.use_outer_join">false</property>
        <property name="hibernate.transaction.factory_class">net.sf.hibernate.transaction.JTATransactionFactory</property>
        <property name="hibernate.transaction.manager_lookup_class">net.sf.hibernate.transaction.JBossTransactionManagerLookup</property>
        <property name="jta.UserTransaction">java:/UserTransaction</property>

      <!-- For debugging: remove/set to true in production -->
        <property name="hibernate.cglib.use_reflection_optimizer">false</property>

        <!-- mapping files -->
        <mapping resource="nl/sogeti/piloot/server/admin/model/Authorisation.hbm.xml"/>
        <mapping resource="nl/sogeti/piloot/server/admin/model/Subscription.hbm.xml"/>
        <mapping resource="nl/sogeti/piloot/server/admin/model/Book.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

  <assembly-descriptor>
     <container-transaction>
      <method>
         <ejb-name>RA_HiLoGenerator</ejb-name>
          <method-name>*</method-name>
       </method>
       <trans-attribute>RequiresNew</trans-attribute>
    </container-transaction>
  </assembly-descriptor>

Caused by: java.sql.SQLException: You cannot commit during a managed transaction!
   at org.jboss.resource.adapter.jdbc.BaseWrapperManagedConnection.jdbcCommit(BaseWrapperManagedConnection.java:490)
   at org.jboss.resource.adapter.jdbc.WrappedConnection.commit(WrappedConnection.java:465)
   at net.sf.hibernate.id.TableGenerator.generate(TableGenerator.java:126)
   at net.sf.hibernate.id.TableHiLoGenerator.generate(TableHiLoGenerator.java:59)
   at nl.sogeti.piloot.server.util.HiLoGeneratorBean.next(HiLoGeneratorBean.java:72)
   ... 118 more

public class HiLoGeneratorBean extends DBSessionBeanBase
{
   /**
    * Having these instance variable will work fine even for a
    * stateless session bean. Each instance will have a unique
    * high number, which is fine.
    */
   private int high = 0;
   private int low = 0;

   /**
    * @ejb.interface-method
    * @ejb.facade-method
    */
   public Long next() throws HibernateException
   {
      if (high == 0)
      {
         try
         {
            DataSource ds = getDataSource();
            Connection connection = ds.getConnection();
            //connection.setAutoCommit(false);
            Statement getHighStatement = connection.createStatement();
            getHighStatement.execute("select max(next_hi) from hibernate_unique_key");
            getHighStatement.getResultSet().next();
            high = getHighStatement.getResultSet().getInt(1);
            Statement updateHighStatement = connection.createStatement();
            updateHighStatement.execute("update hibernate_unique_key set next_hi = " + (high + 1) + " where next_hi = " + high);
            connection.close();
         }
         catch (ApplicationException e)
         {
            throw new HibernateException(e);
         }
         catch (SQLException e)
         {
            throw new HibernateException(e);
         }
      }
      
      long next = ((long)high << 32) + low;
      low++;
      
      return new Long(next);
   }

   public DataSource getDataSource() throws ApplicationException
   {
      try
      {
         InitialContext ic = new InitialContext();
         DataSource dataSource = (DataSource) ic.lookup(EjbConstants.JNDI_DATABASE);

         return dataSource;
      }
      catch (NamingException ne)
      {
         throw new ApplicationException(ApplicationExceptionCodes.DATABASE_OPENING_FAILED, log, ne);
      }
   }
}