Hello!
I have little problem with a basic hibernate configuration.
I'll be very grateful if someone could help me.

Files:

Event.java
------------------------------
package events;

public class Event {

    public Long id;
    public String nazwa_klienta;

    public Event() {}

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getNazwa_klienta() {
        return nazwa_klienta;
    }

    public void setNazwa_klienta(String nazwa_klienta) {
        this.nazwa_klienta = nazwa_klienta;
    }

}

Event.hbm.xml
----------------------------
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="events">
 <class name="Event" table="Klienci">
     <id name="id" column="id">
        <generator class="sequence">
            <param name="sequence">klienci_id_seq</param>
        </generator>
    </id>
    <property name="nazwa_klienta"/>
 </class>
</hibernate-mapping>

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>
    <!-- Database connection settings -->
    <property name="connection.driver_class">org.postgresql.Driver</
property>
    <property name="connection.url">jdbc:postgresql://localhost/Dane_ref</
property>
    <property name="connection.username">postgres</property>
    <property name="connection.password">mykmyk</property>

    <!-- SQL dialect -->
    <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</
property>
    <!-- Enable Hibernate's automatic session context management -->
    <property name="current_session_context_class">thread</property>
    <!-- Disable the second-level cache -->
    <property
name="cache.provider_class">org.hibernate.cache.NoCacheProvider</
property>
    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">true</property>
    <!-- Use the Hibernate built-in pool for tests. -->
    <property name="connection.pool_size">1</property>
    <property
name="cache.provider_class">org.hibernate.cache.NoCacheProvider</
property>
    <property name="cache.use_query_cache">false</property>
    <property name="cache.use_minimal_puts">false</property>
    <property name="max_fetch_depth">3</property>
    <!-- Print SQL to stdout. -->
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <!-- Drop and then re-create schema on SessionFactory build, for
testing. -->
    <!-- Bind the getCurrentSession() method to the thread (don't use for
EJBs) -->
    <property name="current_session_context_class">thread</property>
    <!-- Batch inserts are currently broken, no idea why... -->
    <property name="jdbc.batch_size">0</property>

    <mapping resource="events/Event.hbm.xml" />

</session-factory>
</hibernate-configuration>

EventManager.java
-------------------------------
package events;

import org.hibernate.Session;

import util.HibernateUtil;

public class EventManager {

    private static Session session;
   public Session getSession(){
       return EventManager.session;
   }

    public void polacz() {
        session = HibernateUtil.getSessionFactory().openSession();
    }

}

Start.java
---------------
package events;

public class Start {

    private EventManager mgr = null;
    boolean tak;

    public Start(){
        mgr = new EventManager();
        //mgr.polacz();
    }
    public static void main(String[] args) {
        Start start = new Start();

        start.mgr.polacz();
    }
}

HibernateUtil.java
----------------------------
package util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.*;

public class HibernateUtil {
    private static final SessionFactory sessionFactory;
        static {
            try {

                //Create the SessionFactory from hibernate.cfg.xml

                Configuration cfg = new Configuration();
                cfg.configure("hibernate.cfg.xml");

                //cfg.setProperty("hibernate.connection.password", "grasz");

                sessionFactory =cfg.buildSessionFactory();

            }catch (Throwable ex) {
                //    Make sure you log the exception, as it might be swallowed
                System.err.println("*************************Initial
SessionFactory creation failed." + ex);
                throw new ExceptionInInitializerError(ex);
            }
        }
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

And I have follows errors:
----------------------------------------------

*************************Initial SessionFactory creation
failed.java.lang.ExceptionInInitializerError
Exception in thread "main" java.lang.ExceptionInInitializerError
    at util.HibernateUtil.<clinit>(HibernateUtil.java:24)
    at events.EventManager.polacz(EventManager.java:15)
    at events.Start.main(Start.java:15)
Caused by: java.lang.ExceptionInInitializerError
    at util.HibernateUtil.<clinit>(HibernateUtil.java:14)
    ... 2 more
Caused by: org.apache.commons.logging.LogConfigurationException:
java.lang.NullPointerException
    at org.apache.commons.logging.LogFactory.newFactory(LogFactory.java:
558)
    at org.apache.commons.logging.LogFactory.getFactory(LogFactory.java:
355)
    at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:390)
    at org.hibernate.cfg.Configuration.<clinit>(Configuration.java:116)
    ... 3 more
Caused by: java.lang.NullPointerException
    at org.apache.commons.logging.LogFactory.newFactory(LogFactory.java:
543)
    ... 6 more

Thanks for any advice
Regi