Erro estranho no hibernate

Exception in thread "AWT-EventQueue-0" java.lang.ExceptionInInitializerError
    at dao.GeralDAO.<init>(GeralDAO.java:19)
    at forms.apscoisa.posteriorActionPerformed(apscoisa.java:150)
    at forms.apscoisa.access$100(apscoisa.java:17)
    at forms.apscoisa$2.actionPerformed(apscoisa.java:72)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
    at java.awt.Component.processMouseEvent(Component.java:6041)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
    at java.awt.Component.processEvent(Component.java:5806)
    at java.awt.Container.processEvent(Container.java:2058)
    at java.awt.Component.dispatchEventImpl(Component.java:4413)
    at java.awt.Container.dispatchEventImpl(Container.java:2116)
    at java.awt.Component.dispatchEvent(Component.java:4243)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
    at java.awt.Container.dispatchEventImpl(Container.java:2102)
    at java.awt.Window.dispatchEventImpl(Window.java:2440)
    at java.awt.Component.dispatchEvent(Component.java:4243)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

import java.util.Collection;

import org.hibernate.Criteria;

import org.hibernate.Session;

import org.hibernate.Transaction;

import database.Database;

import java.util.Collection;

public class GeralDAO {

//Operacoes generalizadas

protected static final int INSERIR = 1;

protected static final int ATUALIZAR = 2;

protected static final int REMOVER = 3;

//Sessao com o hibernate

private Session session;

public GeralDAO(){

session = Database.getInstance().getSession();

}

public GeralDAO(Session sessao){

session = sessao;

}

//Retorna sessao
protected Session getSession() {
   if (session == null) {
     session = Database.getInstance().getSession();
   }
   return session;
}
//Fecha sessao
protected void closeSession(){
   if (session != null)
      session.close();
}

public void change(Object obj, int operacao){
    switch (operacao) {
         case INSERIR:
         case ATUALIZAR:
             session.saveOrUpdate(obj);
         break;
         case REMOVER:
             session.delete(obj);
         break;
    }
}

//Persiste objeto
public void create(Object obj){
  change(obj, INSERIR);
}
//Atualiza objeto
public void update(Object obj){
  change(obj, ATUALIZAR);
}
//Remove objeto
public void delete(Object obj){
  change(obj, REMOVER);
}
//Busca pela chave primária
public Object findByPrimaryKey(Class classe, int id){
  return session.get(classe, id);
}

public Collection findAll(Class classe){

try{

Criteria criteria = getSession().createCriteria(classe);

return criteria.list();

}finally{

getSession().close();

}

}