Javax.persistence.TransactionRequiredException: no transaction is in progress

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0"
	xmlns="http://java.sun.com/xml/ns/persistence">
	<persistence-unit name="JIMAGE" transaction-type="RESOURCE_LOCAL">
		<provider>org.hibernate.ejb.HibernatePersistence</provider>
		<class>br.uninove.jimage.to.MetodosDeClassificacaoTO</class>
		<properties>
			<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
			<property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />

			<property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/jimage" />
			<property name="hibernate.connection.password" value="******" />
			<property name="hibernate.connection.username" value="root" />
			<property name="hibernate.hbm2ddl.auto" value="update" />

			<property name="hibernate.show_sql" value="true" />
			<property name="hibernate.format_sql" value="true" />

			<property name="hibernate.transaction.auto_close_session" value="true" />
			<property name="hibernate.transaction.flush_before_completion" value="true" />
		</properties>
	</persistence-unit>
</persistence>

@Entity
@Table(name = "METODOS_DE_CLASSIFICAO")
@NamedQueries({
    @NamedQuery(name = "MetodosDeClassificacaoTO.findAll", query = "SELECT m FROM MetodosDeClassificacaoTO m"),
    @NamedQuery(name = "MetodosDeClassificacaoTO.findById", query = "SELECT m FROM MetodosDeClassificacaoTO m WHERE m.id = :id"),
    @NamedQuery(name = "MetodosDeClassificacaoTO.findByNome", query = "SELECT m FROM MetodosDeClassificacaoTO m WHERE m.nome = :nome")})
public class MetodosDeClassificacaoTO implements Serializable {

	
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @Column(name = "ID")
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    @Basic(optional = false)
    @Column(name = "NOME")
    private String nome;

gets sets...

package br.uninove.jimage.dao;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import br.uninove.jimage.to.MetodosDeClassificacaoTO;

public class JImageDao {

	private EntityManager em;
	
	public JImageDao(){
		if ( em == null ) {
			EntityManagerFactory emf = Persistence.createEntityManagerFactory("JIMAGE");
			em = emf.createEntityManager();
		}
	}
	....
	
	public void saveMetodosDeClassificacao(MetodosDeClassificacaoTO to){
		em.persist(to);  
		em.flush();
	}
	
	
	public static void main(String[] args) {
		JImageDao dao = new JImageDao();

		MetodosDeClassificacaoTO to1 = new MetodosDeClassificacaoTO();
		MetodosDeClassificacaoTO to2 = new MetodosDeClassificacaoTO();
		MetodosDeClassificacaoTO to3 = new MetodosDeClassificacaoTO();
		MetodosDeClassificacaoTO to4 = new MetodosDeClassificacaoTO();
		MetodosDeClassificacaoTO to5 = new MetodosDeClassificacaoTO();
		
		to1.setNome("Matriz de Co-ocorrência");
		to2.setNome("Matriz de Comprimento");
		to3.setNome("Matriz de Diferença de Níveis de Cinza");
		to4.setNome("Matriz de Soma e Diferença do Histograma");
		to5.setNome("Matriz do Momento do Histograma");
		
		dao.saveMetodosDeClassificacao(to1);
		dao.saveMetodosDeClassificacao(to2);
		dao.saveMetodosDeClassificacao(to3);
		dao.saveMetodosDeClassificacao(to4);
		dao.saveMetodosDeClassificacao(to5);
	}
}

23:26:07,536 DEBUG QueryTranslatorImpl:239 - HQL: SELECT m FROM br.uninove.jimage.to.MetodosDeClassificacaoTO m WHERE m.nome = :nome
23:26:07,536 DEBUG QueryTranslatorImpl:240 - SQL: select metodosdec0_.ID as ID2_, metodosdec0_.NOME as NOME2_ from METODOS_DE_CLASSIFICAO metodosdec0_ where metodosdec0_.NOME=?
23:26:07,536 DEBUG ErrorCounter:91 - throwQueryException() : no errors
23:26:07,537 DEBUG SessionFactoryImpl:446 - Checking 0 named SQL queries
23:26:07,566 DEBUG SessionImpl:247 - opened session at timestamp: [telefone removido]
23:26:07,578 DEBUG AbstractSaveEventListener:330 - delaying identity-insert due to no transaction in progress
Exception in thread "main" javax.persistence.TransactionRequiredException: no transaction is in progress
	at org.hibernate.ejb.AbstractEntityManagerImpl.flush(AbstractEntityManagerImpl.java:301)
	at br.uninove.jimage.dao.JImageDao.saveMetodosDeClassificacao(JImageDao.java:33)
	at br.uninove.jimage.dao.JImageDao.main(JImageDao.java:53)