<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>

      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();
      
      //cria primeira composição
      ItemPecaEstrutural item1 = new ItemPecaEstrutural();
      item1.setQuantidade(44);
      item1.setTotal(new BigDecimal("334.43"));      

      DescricaoMaterial descricaoMaterial1 = new DescricaoMaterial();
      sessao.load(descricaoMaterial1,new Integer(1));
      item1.setDescricaoMaterial(descricaoMaterial1);
      pecaEstrutural.addItem(item1);
      
      //cria segunda composição
      ItemPecaEstrutural item2 = new ItemPecaEstrutural();
      item2.setQuantidade(34);
      item2.setTotal(new BigDecimal("4.43"));
      DescricaoMaterial descricaoMaterial2 = new DescricaoMaterial();
      sessao.load(descricaoMaterial2,new Integer(2));
      item2.setDescricaoMaterial(descricaoMaterial2);
      pecaEstrutural.addItem(item2);
      
      Integer pk = pecaEstrutural.getId();
      trans.commit();
      sessao.close();

Initializing c3p0 pool... com.mchange.v2.c3p0.PoolBackedDataSource@134263a [ connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@5db5ae [ acquireIncrement -> 1, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, idleConnectionTestPeriod -> 3000, initialPoolSize -> 5, maxIdleTime -> 300, maxPoolSize -> 20, maxStatements -> 50, maxStatementsPerConnection -> 0, minPoolSize -> 5, nestedDataSource -> com.mchange.v2.c3p0.DriverManagerDataSource@2d59a3 [ description -> null, driverClass -> null, factoryClassLocation -> null, jdbcUrl -> jdbc:firebirdsql://servidor:3050/c:\SOR\BANCO.FDB, properties -> {user=******, password=******, lc_ctype=WIN1252} ] , preferredTestQuery -> null, propertyCycle -> 300, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, usesTraditionalReflectiveProxies -> false ] , factoryClassLocation -> null, numHelperThreads -> 3, poolOwnerIdentityToken -> 134263a ]
11:04:27,695Hibernate: select gen_id( PECA_ESTRUTURAL_GEN, 1 ) from RDB$DATABASE
Hibernate: select descricaom0_.DESCRICAO_MATERIAL_ID as DESCRICAO1_0_, descricaom0_.VERSAO as VERSAO2_0_, descricaom0_.nome as nome2_0_, descricaom0_.UNIDADE_MEDIDA as UNIDADE4_2_0_ from DESCRICAO_MATERIAL descricaom0_ where descricaom0_.DESCRICAO_MATERIAL_ID=?
Hibernate: insert into PECA_ESTRUTURAL (VERSAO, descricao, QTD_CHARUTOS, TIPO, PECA_ESTRUTURAL_ID) values (?, ?, ?, 'Portico', ?)
Hibernate: select gen_id(
                  ITEM_PECA_ESTRUTURAL_GEN
               , 1 ) from RDB$DATABASE
Hibernate: insert into ITEM_PECA_ESTRUTURAL (PECA_ESTRUTURAL_ID, ITEM_PECA_ESTRUTURAL_ID, quantidade, total, DESCRICAO_MATERIAL_ID) values (?, ?, ?, ?, ?)
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=?
Hibernate: update PECA_ESTRUTURAL set VERSAO=?, descricao=?, QTD_CHARUTOS=? where PECA_ESTRUTURAL_ID=? and VERSAO=?
Hibernate: select gen_id(
                  ITEM_PECA_ESTRUTURAL_GEN
               , 1 ) from RDB$DATABASE
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.id.SequenceGenerator.generate(SequenceGenerator.java:91)
   at org.hibernate.collection.PersistentIdentifierBag.preInsert(PersistentIdentifierBag.java:294)
   at org.hibernate.persister.collection.AbstractCollectionPersister.insertRows(AbstractCollectionPersister.java:1007)
   at org.hibernate.action.CollectionUpdateAction.execute(CollectionUpdateAction.java:48)
   at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239)
   at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223)
   at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:139)
   at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:274)11:04:48,69511:04:48,695
   at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
   at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:675)
   at src.testeGerenciarPecaEstrutural.main(testeGerenciarPecaEstrutural.java:53)
org.firebirdsql.jdbc.FBSQLException: This statement is already closed.
   at org.firebirdsql.jdbc.AbstractStatement.close(AbstractStatement.java:225)
   at com.mchange.v1.db.sql.StatementUtils.attemptClose(StatementUtils.java:38)
   at com.mchange.v2.c3p0.stmt.GooGooStatementCache$1.run(GooGooStatementCache.java:246)
   at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:354)
11:04:48,715org.hibernate.exception.GenericJDBCException: could not get next sequence value
   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.id.SequenceGenerator.generate(SequenceGenerator.java:96)
   at org.hibernate.collection.PersistentIdentifierBag.preInsert(PersistentIdentifierBag.java:294)
   at org.hibernate.persister.collection.AbstractCollectionPersister.insertRows(AbstractCollectionPersister.java:1007)
   at org.hibernate.action.CollectionUpdateAction.execute(CollectionUpdateAction.java:48)
   at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239)
   at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:223)
   at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:139)
   at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:274)
   at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
   at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:675)
   at src.testeGerenciarPecaEstrutural.main(testeGerenciarPecaEstrutural.java:53)
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.id.SequenceGenerator.generate(SequenceGenerator.java:91)
   ... 10 more