Tela de login com primefaces

<h:form prependId="false">
	   		<p:dialog header="Area restrita"
	   				  modal="true"
	   				  closable="false"
	   				  position="center"
	   				  widgetVar="modalLogin"
	   				  minWidth="300"
	   				  width="300"
	   				  showEffect="slide" 
	   		    	  draggable="false"
	   		    	  resizable="false"
	   		    	  visible="true">		 
	   			<center>	 
				   	<p:messages id="mensagens" showDetail="true" showSummary="false" />    				 
		   			<h:panelGrid columns="2">   		
				      	<h:outputLabel value="Login" />
		     			<h:inputText id="j_username" size="15" />
				 		<h:outputLabel value="Senha" />
						<h:inputSecret id="j_password" size="15" />
					</h:panelGrid>
					<br />	
					<h:commandButton value="Entrar" action="#{loginMB.logar}" />		
				</center>
			</p:dialog>
	 	</h:form>

public String logar() {
		try {
		    RequestDispatcher dispatcher = FacesUtil.getServletRequest().getRequestDispatcher("/j_spring_security_check");
		    dispatcher.forward(FacesUtil.getServletRequest(), FacesUtil.getServletResponse());
		    FacesContext.getCurrentInstance().responseComplete();
		} catch (Exception ex) {
			FacesUtil.exibirMensagemErro(ex.getMessage());
			return null;
		}
	    return null;
	}
	
	public String logout() {
		FacesUtil.exibirMensagemAlerta("Sess�o finalizada com sucesso");
		try {
			RequestDispatcher dispatcher = FacesUtil.getServletRequest().getRequestDispatcher("/j_spring_security_logout");
			dispatcher.forward(FacesUtil.getServletRequest(), FacesUtil.getServletResponse());
			FacesContext.getCurrentInstance().responseComplete();
		} catch (Exception ex) {
			FacesUtil.exibirMensagemErro("Erro ao sair do sistema");
			return null;
		}
		return null;
	}

@Service("hibernateUserDetailsService")
public class HibernateUserDetailsService extends HibernateDaoSupport implements UserDetailsService  {
	@Autowired
	public HibernateUserDetailsService(SessionFactory sessionFactory) {
		setSessionFactory(sessionFactory);
	}

	@SuppressWarnings("unchecked")
	@Override
	public UserDetails loadUserByUsername(String login) {
		DetachedCriteria criteria = DetachedCriteria.forClass(Usuario.class, "usuario");
		criteria.add(Restrictions.eq("usuario.login", login));
		List resultado = getHibernateTemplate().findByCriteria(criteria);
		if(resultado != null && resultado.size() == 0) {
			throw new UsernameNotFoundException("Usuario nao encontrado!");
	    }	
		return (Usuario)resultado.get(0);
	}
}

<bean class="springframework.orm.hibernate3.HibernateExceptionTranslator"/>
   <bean id="sessionFactory"   class="springframework.orm.hibernate3.LocalSessionFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<property name="annotatedClasses">
			<list>
				<value>br.com.exemploseguranca.entity.Usuario</value>
				<value>br.com.exemploseguranca.entity.Perfil</value>
				<value>br.com.exemploseguranca.entity.Carreta</value>
			</list>
		</property>
		<property name="hibernateProperties">
			<props>
				<prop key="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</prop>
				<prop key="hibernate.show_sql">true</prop>
			</props>
		</property>
	</bean>