Two sessions no hibernate

ClienteDao clienteDao = new ClienteDao();
            cliente = clienteDao.getClienteById(getPes_id());

            VendedorDao vendedorDao = new VendedorDao();
            vendedor = vendedorDao.getVendedorByCod(vendedorLogin.getCodigo());

            if (cliente.getVen_id().getPes_id() != vendedor.getPes_id()) {
                System.out.println("Erro");
            } else {
                System.out.println("Cliente deletado");
                try{
                    clienteDao.excluir(cliente);
                }catch(Exception e){
                    e.printStackTrace();
                }
            }

public class HibernateUtil {
    private static SessionFactory sessionFactory;
    static {
        try {
            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
    public static SessionFactory getSessionFactory() {
        if (sessionFactory == null) {
            try {
                sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
            } catch (Throwable ex) {
                System.err.println("Initial SessionFactory creation failed." + ex);
                throw new ExceptionInInitializerError(ex);
            }

        }
        return sessionFactory;
    }
    public static Session getSession() {
        return sessionFactory
                .getCurrentSession();
    }
    public static Session openSession() {
        return sessionFactory
                .openSession();
    }
}

public class VendedorDao {
    Vendedor vendedor;
    public VendedorDao() {
    }
    public void incluir(Vendedor e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.saveOrUpdate(e);
        tx.commit();
    }
    public void atualizar(Vendedor e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.saveOrUpdate(e);
        tx.commit();
    }
    public void excluir(Vendedor e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.delete(e);
        tx.commit();
    }
    public Vendedor getVendedorById(long id) {
        Session session = HibernateUtil.getSession();
        return (Vendedor) session.get(Vendedor.class, id);
    }
    public Vendedor getVendedorByCod(long codigo){
        Session session = HibernateUtil.openSession();
        return (Vendedor) session.createCriteria(Vendedor.class)
                    .add(Restrictions.eq("ven_codigo", codigo))
                    .uniqueResult();
    }
}

public class ClienteDao {
    Cliente cliente;
    public ClienteDao() {
    }
    public void incluir(Cliente e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.saveOrUpdate(e);
        tx.commit();
    }

    public void atualizar(Cliente e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.saveOrUpdate(e);
        tx.commit();
    }
    public void excluir(Cliente e) {
        Session session = HibernateUtil.getSession();
        Transaction tx = session.beginTransaction();
        session.delete(e);
        tx.commit();
    }
    public Cliente getClienteById(long pes_id) {
        Session session = HibernateUtil.openSession();
        return (Cliente) session.get(Cliente.class, pes_id);
    }
    public List<Cliente> getClienteByVendedor(Vendedor vendedor) {
        Session session = HibernateUtil.openSession();
        return session.createCriteria(Cliente.class)
                    .add(Restrictions.eq("ven_id", vendedor))
                    .list();
    }
}

public class HibernateUtil {  
    private static SessionFactory sessionFactory;  
    static {  
        try {  
            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();  
        } catch (Throwable ex) {  
            System.err.println("Initial SessionFactory creation failed." + ex);  
            throw new ExceptionInInitializerError(ex);  
        }  
    }  
    public static SessionFactory getSessionFactory() {  
        if (sessionFactory == null) {  
            try {  
                sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();  
            } catch (Throwable ex) {  
                System.err.println("Initial SessionFactory creation failed." + ex);  
                throw new ExceptionInInitializerError(ex);  
            }  
  
        }  
        return sessionFactory;  
    }  
    public static Session getSession() {  
        return sessionFactory  
                .getCurrentSession();  
    }  
    public static Session openSession() {  
        return sessionFactory  
                .openSession();  
    }  
}

public class HibernateUtil {  
    private static SessionFactory sessionFactory;  
    static {  
        try {  
            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();  
        } catch (Throwable ex) {  
            System.err.println("Initial SessionFactory creation failed." + ex);  
            throw new ExceptionInInitializerError(ex);  
        }  
    }  
    
    public static Session getSession() {  
        return sessionFactory  
                .getCurrentSession();  
    }  

}

public void incluir(Vendedor e) {  
        Session session = HibernateUtil.getSession();  
        Transaction tx = session.beginTransaction();  
        session.saveOrUpdate(e);  
        tx.commit();  
        session.close();
    }

"Illegal attempt to associate a collection with two open sessions"