新出现的hibernate问题

这段异常是什么意思???
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
ssssException in thread "main"
java.lang.NullPointerException
at com.wangchao.struts.HibernateUitl.currentSession(HibernateUitl.java:25)
at com.wangchao.struts.AdminDAOFactory.main(AdminDAOFactory.java:19)