Hibernate. erro ao salvar objeto com + de 2 itens [resolvido]

public static void main(String[] args) {
		Session session = HibernateUtil.getSession();
		Transaction trans = session.beginTransaction();
		PecaEstrutural pecaEstrutural = new Portico();
		pecaEstrutural.setDescricao("Portico teste 50metros de vão");
		pecaEstrutural.setQuantidadeCharutos(4);
		session.saveOrUpdate(pecaEstrutural);
		List lista = pecaEstrutural.getItens();
	//	session.lock(pecaEstrutural,LockMode.NONE);
		
		ItemPecaEstrutural item1 = new ItemPecaEstrutural();
		item1.setQuantidade(44);
		item1.setTotal(new BigDecimal("334.43"));		
		Session sessao1 = HibernateUtil.getSession();
		DescricaoMaterial descricaoMaterial1 = new DescricaoMaterial(); 
		sessao1.load(descricaoMaterial1,new Integer(1));
		sessao1.close();
		item1.setDescricaoMaterial(descricaoMaterial1);
		pecaEstrutural.addItem(item1);
		
		ItemPecaEstrutural item2 = new ItemPecaEstrutural();
		item2.setQuantidade(34);
		item2.setTotal(new BigDecimal("4.43"));
		Session sessao2 = HibernateUtil.getSession();
		DescricaoMaterial descricaoMaterial2 = new DescricaoMaterial(); 
		sessao2.load(descricaoMaterial2,new Integer(2));
		sessao2.close();
		item2.setDescricaoMaterial(descricaoMaterial2);
		pecaEstrutural.addItem(item2);
		
		Integer pk = pecaEstrutural.getId();
		trans.commit();
		session.close();
		
		Session sessao3 = HibernateUtil.getSession();
		PecaEstrutural pe = new Portico();
		sessao3.load(pe,pk);
		
		assert pk == pe.getId(): "Não foi gravado.";
	}

<hibernate-mapping>

	<class name="src.model.PecaEstrutural" table="PECA_ESTRUTURAL">

		<id name="id" column="PECA_ESTRUTURAL_ID">
			<generator class="sequence">
				<param name="sequence">PECA_ESTRUTURAL_GEN</param>
			</generator>
		</id>

		<discriminator column="TIPO"/>

		<version name="versao" column="VERSAO" />

		<property name="descricao" unique="true" not-null="true" />

		<property name="quantidadeCharutos" column="QTD_CHARUTOS" not-null="true" />

		<idbag name="itens" lazy="true" cascade="all-delete-orphan"
			table="ITEM_PECA_ESTRUTURAL">
			<collection-id type="integer"
				column="ITEM_PECA_ESTRUTURAL_ID">
				<generator class="sequence">
					<param name="sequence">
						ITEM_PECA_ESTRUTURAL_GEN
					</param>
				</generator>
			</collection-id>
			<key column="PECA_ESTRUTURAL_ID" not-null="true" />
			<composite-element class="src.model.ItemPecaEstrutural">
				<property name="quantidade" />
				<property name="total" />
				<many-to-one name="descricaoMaterial" column="DESCRICAO_MATERIAL_ID" />
			</composite-element>
		</idbag>
		
		<subclass
			name="src.model.Tesoura"
			discriminator-value="Tesoura">
		</subclass>			
		
		<subclass
			name="src.model.Portico"
			discriminator-value="Portico">
		</subclass>					

	</class>

</hibernate-mapping>


<hibernate-mapping>

        <class name="src.model.DescricaoMaterial" table="DESCRICAO_MATERIAL">
                
                <id name="id" column="DESCRICAO_MATERIAL_ID">
                        <generator class="sequence">
                        	<param name="sequence">DESCRICAO_MATERIAL_GEN</param>
                        </generator>
                </id>
                
                <version name="versao" column="VERSAO"/>

                <property name="nome" unique="true" not-null="true"/>

				<property name="unidadeMedida" column="UNIDADE_MEDIDA" not-null="true"/>

        </class>

</hibernate-mapping>

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

	private static final SessionFactory sessionFactory;
	
	static {
		try { 
			Configuration cfg = new Configuration();
			sessionFactory = cfg.configure().buildSessionFactory();
		} catch (Throwable ex) {
			ex.printStackTrace(System.out);
			throw new ExceptionInInitializerError(ex);
		}
	}
	
	public static Session getSession() throws HibernateException {
		return sessionFactory.openSession();
	}	

	public static void excluir(Object objeto) {
		Session session = getSession();
		Transaction transacao = session.beginTransaction();
		try{
			session.delete(objeto);
			transacao.commit();
		} finally {
			session.close();
		}
	}	
	
	public static void salvar(Object objeto) {
		Session session = HibernateUtil.getSession();
		Transaction transacao = session.beginTransaction();
		try {
			session.saveOrUpdate(objeto);
			transacao.commit();
		} finally{
		session.close();
		}
	}	
	
}

public class testeGerenciarPecaEstrutural {

	public static void main(String[] args) {
		Session sessao = HibernateUtil.getSession();
		Transaction trans = sessao.beginTransaction();
		//cria objeto composto
		PecaEstrutural pecaEstrutural = new Portico();
		pecaEstrutural.setDescricao("Portico teste 50metros de vão");
		pecaEstrutural.setQuantidadeCharutos(4);
		sessao.saveOrUpdate(pecaEstrutural);
		List lista = pecaEstrutural.getItens();
	//	session.lock(pecaEstrutural,LockMode.NONE);
		
		//cria primeira composição
		ItemPecaEstrutural item1 = new ItemPecaEstrutural();
		item1.setQuantidade(44);
		item1.setTotal(new BigDecimal("334.43"));		
	//	Session sessao1 = HibernateUtil.getSession();
	//	Transaction trans1 = sessao1.beginTransaction();
		DescricaoMaterial descricaoMaterial1 = new DescricaoMaterial(); 
		sessao.load(descricaoMaterial1,new Integer(1));
	//	trans1.commit();
	//	sessao1.close();
		item1.setDescricaoMaterial(descricaoMaterial1);
		pecaEstrutural.addItem(item1);
		
		//cria segunda composição
		ItemPecaEstrutural item2 = new ItemPecaEstrutural();
		item2.setQuantidade(34);
		item2.setTotal(new BigDecimal("4.43"));
	//	Session sessao2 = HibernateUtil.getSession();
	//	Transaction trans2 = sessao2.beginTransaction();
		DescricaoMaterial descricaoMaterial2 = new DescricaoMaterial(); 
           // dá erro ao fazer esse load
		sessao.load(descricaoMaterial2,new Integer(2));
	//	trans2.commit();
	//	sessao2.close();
		item2.setDescricaoMaterial(descricaoMaterial2);
		pecaEstrutural.addItem(item2);
		
		Integer pk = pecaEstrutural.getId();
		trans.commit();
		sessao.close();
		
		Session sessao3 = HibernateUtil.getSession();
		PecaEstrutural pe = new Portico();
		sessao3.load(pe,pk);
		
		assert pk == pe.getId(): "Não foi gravado.";
	}

}

Hibernate: select descricaom0_.DESCRICAO_MATERIAL_ID as DESCRICAO1_0_, descricaom0_.VERSAO as VERSAO2_0_, descricaom0_.nome as nome2_0_, descricaom0_.UNIDADE_MEDIDA as UNIDADE4_2_0_ from DESCRICAO_MATERIAL descricaom0_ where descricaom0_.DESCRICAO_MATERIAL_ID=?
Problem with checked-in Statement, discarding.
java.lang.NullPointerException
	at org.firebirdsql.jdbc.AbstractPreparedStatement.clearParameters(AbstractPreparedStatement.java:349)
	at com.mchange.v2.c3p0.stmt.GooGooStatementCache.refreshStatement(GooGooStatementCache.java:410)
	at com.mchange.v2.c3p0.stmt.GooGooStatementCache.checkinStatement(GooGooStatementCache.java:129)
	at com.mchange.v2.c3p0.impl.NewPooledConnection.checkinStatement(NewPooledConnection.java:143)
	at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.close(NewProxyPreparedStatement.java:1670)
	at org.hibernate.jdbc.AbstractBatcher.closePreparedStatement(AbstractBatcher.java:393)
	at org.hibernate.jdbc.AbstractBatcher.closeStatement(AbstractBatcher.java:195)
	at org.hibernate.jdbc.AbstractBatcher.closeQueryStatement(AbstractBatcher.java:212)
	at org.hibernate.jdbc.AbstractBatcher.closeQueryStatement(AbstractBatcher.java:141)
	at org.hibernate.loader.Loader.getResultSet(Loader.java:1207)
	at org.hibernate.loader.Loader.doQuery(Loader.java:366)
	at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:206)
	at org.hibernate.loader.Loader.loadEntity(Loader.java:1271)
	at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:141)
	at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:126)
	at org.hibernate.persister.entity.BasicEntityPersister.load(BasicEntityPersister.java:2496)
	at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:387)
	at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:368)
	at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:166)
	at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:140)
	at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:249)
	at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:123)
	at org.hibernate.impl.SessionImpl.load(SessionImpl.java:540)
	at src.testeGerenciarPecaEstrutural.main(testeGerenciarPecaEstrutural.java:45)
10:55:15,70110:55:15,701Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not load an entity: [src.model.DescricaoMaterial#2]
	at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:82)
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:70)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
	at org.hibernate.loader.Loader.loadEntity(Loader.java:1285)
	at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:141)
	at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:126)
	at org.hibernate.persister.entity.BasicEntityPersister.load(BasicEntityPersister.java:2496)
	at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:387)
	at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:368)
	at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:166)
	at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:140)
	at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:249)
	at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:123)
	at org.hibernate.impl.SessionImpl.load(SessionImpl.java:540)
	at src.testeGerenciarPecaEstrutural.main(testeGerenciarPecaEstrutural.java:45)
Caused by: org.firebirdsql.jdbc.FBSQLException: This statement is already closed.
	at org.firebirdsql.jdbc.AbstractStatement.close(AbstractStatement.java:225)
	at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.close(NewProxyPreparedStatement.java:1674)
	at org.hibernate.jdbc.AbstractBatcher.closePreparedStatement(AbstractBatcher.java:393)
	at org.hibernate.jdbc.AbstractBatcher.closeStatement(AbstractBatcher.java:195)
	at org.hibernate.jdbc.AbstractBatcher.closeQueryStatement(AbstractBatcher.java:212)
	at org.hibernate.jdbc.AbstractBatcher.closeQueryStatement(AbstractBatcher.java:141)
	at org.hibernate.loader.Loader.getResultSet(Loader.java:1207)
	at org.hibernate.loader.Loader.doQuery(Loader.java:366)
	at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:206)
	at org.hibernate.loader.Loader.loadEntity(Loader.java:1271)
	... 11 more

public class ConnectionFactory {
    
    private static final SessionFactory sessionFactory;
    private static final ThreadLocal<Session> threadLocal =
            new ThreadLocal<Session>();
    
    static {
        
        try {
            sessionFactory = new AnnotationConfiguration().configure(
                    "hibernate.cfg.xml").buildSessionFactory();
        } catch (Throwable t) {
            throw new ExceptionInInitializerError(t);
        }
        
    }
    
    public static Session getInstance() {
        Session session = (Session) threadLocal.get();
        session = sessionFactory.openSession();
        threadLocal.set(session);
        return session;
    }
    
}

Session session = ConnectionFactory.getInstance();