I'm developing my first enterpise application with jpa ejb ecc

when i try to save an object i get this error  : java.lang.IllegalStateException: A JTA EntityManager cannot use getTransaction()

this is my persistance.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" 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_2_0.xsd">
    <persistence-unit name="jpa"  transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
         <jta-data-source>java:jboss/newDataSource</jta-data-source>

        <properties>
            <property name="hibernate.hbm2ddl.auto" value="create-drop"/>     
        </properties>

    </persistence-unit> 
</persistence>

and this is my bean

package exampleBean;

import javax.ejb.Stateless;
import javax.ejb.TransactionAttribute;
import javax.ejb.TransactionAttributeType;
import javax.ejb.TransactionManagement;
import javax.ejb.TransactionManagementType;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.transaction.TransactionManager;

import pojo.Privato;

import exampleInterface.ManagedPrivato;

@Stateless
public class ManagedPrivatoBean implements ManagedPrivato {


    @PersistenceContext(unitName="jpa")
    EntityManager em;


    @Override
    public void savePrivato(String nome , String cognome) {
        // TODO Auto-generated method stub
        Privato pr = new Privato();
        pr.setNome(nome);pr.setCognome(cognome);

        em.getTransaction().begin();
        em.persist(pr);
        em.getTransaction().commit();

        System.out.println("Utente Salvato");


    }

    @Override
    public void updatePrivato() {
        // TODO Auto-generated method stub

    }

    @Override
    public void deletePrivato() {
        // TODO Auto-generated method stub

    }

}