Validate user login

Question

I’m not able to validate the user login. Could someone give me a help?

My Dao:

public Login getvalidarLogin(Login login ){

    Session session = HibernateUtil.getSessionFactory().getCurrentSession();
    Transaction t = session.beginTransaction();
    try{
        Query query = session.createQuery("from login where login_login='"+login.getLogin_login()+"' and login_senha='"+login.getLogin_senha()+"'");
        login = (Login)query.uniqueResult();
        t.commit();

    }catch(HibernateException e){
        System.out.println("ERRO AO VALIDAR LOGIN .Erro: >>>>>>" + e.getMessage());
    }
    return login;
}

My Bean:

public String validacaoLogin(){

    login = dao.getvalidarLogin(login);
    if(login != null){
        login = new Login();
        FacesContext.getCurrentInstance().addMessage(null,new FacesMessage(FacesMessage.SEVERITY_ERROR, "Usuário não encontrado!","Erro no Login!"));
        return null;
    } else {
            return "medico/medicoView";
        }
    }