JTA EntityManager cannot access a transactions

Assuntos Gerais
#1

Pessoal, fiz um pesqueno exemplo, só que esta dando erro (JTA EntityManager cannot access a transactions) aqui :

		em.getTransaction().begin();
minha chamada:

		PrecoPorMetodoBean osb = new PrecoPorMetodoBean();
		List<PrecoPorMetodo> resultado1 = osb.selecionaprecopormetodo(metodo.getId().toString());



public class PrecoPorMetodoBean implements PrecoPorMetodoLocal {


	private static EntityManagerFactory emf;
	private static EntityManager em;
	
	@EJB(name = "OrcamentoServiceBean/local")
	private OrcamentoServiceLocal orcamentoService;

	
	public static void startConnection() {
		emf = Persistence.createEntityManagerFactory("lims-pu");
		em = emf.createEntityManager();
		em.getTransaction().begin();
	}
	
	
	public static void closeConnection() {
		em.getTransaction().commit();
		emf.close();
	}
	
	public static EntityManager getEntityManager() {
		return em;
	}

	
	
    public List<PrecoPorMetodo> selecionaprecopormetodo(String vMetodo_id) {
        try {
        	
    		startConnection();
    		
   		
    		closeConnection();

           .........


persistence.xml


<persistence xmlns="http://java.sun.com/xml/ns/persistence"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
    http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
	version="1.0">
	<persistence-unit name="lims-pu" transaction-type="JTA">
	<provider>org.hibernate.ejb.HibernatePersistence</provider>
		<jta-data-source>java:/LimsDS</jta-data-source>
		
			
		<jar-file>../auditor-ejb-${pom.version}.jar</jar-file>
		<jar-file>../usuario-ejb-${pom.version}.jar</jar-file>
		<jar-file>../funcionario-ejb-${pom.version}.jar</jar-file>
		<jar-file>../cliente-ejb-${pom.version}.jar</jar-file>
		<jar-file>../orcamento-ejb-${pom.version}.jar</jar-file>
		<jar-file>../comum-ejb-${pom.version}.jar</jar-file>
		<jar-file>../analise-ejb-${pom.version}.jar</jar-file>
		<jar-file>../coleta-ejb-${pom.version}.jar</jar-file>
		<jar-file>../faturamento-ejb-${pom.version}.jar</jar-file>
		<jar-file>../laudo-ejb-${pom.version}.jar</jar-file>



           
        
		<properties>
	<property name="hibernate.transaction.manager_lookup_class"  
 value="org.hibernate.transaction.JBossTransactionManagerLookup"/>
		
			<property name="hibernate.dialect" value="${hibernate.dialect}" />
			<!-- property name="hibernate.hbm2ddl.auto" value="${hibernate.hbm2ddl}" /-->
			<property name="hibernate.show_sql" value="${hibernate.show_sql}" />

			<property name="hibernate.cache.provider_class" value="${hibernate.cache.provider_class}"/>
			<property name="hibernate.cache.use_second_level_cache" value="${hibernate.cache.use_second_level_cache}"/>
			<property name="hibernate.cache.use_query_cache" value="${hibernate.cache.use_query_cache}"/>
			<property name="hibernate.jdbc.batch_size" value="0" />

		</properties>
	</persistence-unit>
</persistence>
#2