Hibernate version:2.1.6

Mapping documents:

Code between sessionFactory.openSession() and session.close():
try{
Session session = HibernateUtil.currentSession();
Transaction tx = session.beginTransaction();
...
tx.commit();
HibernateUtil.closeSession();
}...

Full stack trace of any exception that occurs:
java.lang.ExceptionInInitializerError
at org.scbit.clinsnp.util.HibernateUtil.<clinit>(HibernateUtil.java:23)
at org.scbit.clinsnp.register.LoginServlet.doPost(LoginServlet.java:36)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
...

Name and version of the database you are using:oracle9i

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:

I use a datasource, and <Resource> element has been added to server.xml, and my "hibernate.cfg.xml" has"
<property name="show_sql">true</property>
<property name="dialect">net.sf.hibernate.dialect.Oracle9Dialect</property>
<property name="connection.datasource">java:/comp/env/jdbc/estap</property>
<property name="statement_cache.size">25</property>
<property name="jdbc.fetch_size">50</property>
<property name="jdbc.batch_size">30</property>".
However, when I run this web application, it always shows wrongs above, and it seems to hava a problem of the code "sessionFactory = new Configuration().configure().buildSessionFactory();" in my hibernate util class file. I have been bothered by these wrong info a whole day, and there is anyone can help me?