Hibernate3 SessionFactory 更新快取的方法

SessionFactory.CONFIG_FILE_LOCATION="/hibernate.cfg.xml";
Object session_id=SessionFactory.createSession();
Session hsession=SessionFactory.getSession();
Query query=null;
MyObject obj=(MyObject)hsession.get(MyObject.class,new Integer(1));
obj.setAttribute("new attribute");
Transaction tx = hsession.beginTransaction();
try {
 hsession.update(obj);
 tx.commit();

 //更新快取
 hsession.refresh(obj);
}
catch(HibernateException e) {
 if(tx != null) {
  try {
          tx.rollback();
  }
  catch(HibernateException ex) {
   ex.printStackTrace();
  }
 }
}
SessionFactory.closeSession(session_id);