Problem to convert with composite key into jsf, selectonemenu

Question

I am making a selectOneMenu where the itemvalue will be a composite key. Which will be separated by a hyphen. However, when sending, the getasobject method is called several times, sending all items from my selectonemenu and not just the selected one.

    @FacesConverter(value = "conversorProd")
public class ConversorProdutoDB implements Converter {

    @Override
    public Object getAsObject(FacesContext facesContext, UIComponent uiComponent, String value) {
        if (value != null && !value.isEmpty()) {
            try {
                String[] split = value.split("-"); //assumindo que será separado (idProduto - idGradeSelecionada)

                if (split.length > 1) {
                    GradeProduto gradeProd = PadraoDAO.carregar(GradeProduto.class, Long.valueOf(split[1]));
                    Produto prodComGrade = gradeProd.getProd();
                    prodComGrade.setGradeSelecionada(gradeProd);
                    return prodComGrade;
                } else {
                    return (Produto) PadraoDAO.carregar(Produto.class, Long.valueOf(split[0]));
                }
            } catch (ExceptionBancoDeDados ex) {
                Logger.getLogger(ConversorProdutoDB.class.getName() + "-Erro ao executar conversor de produto").log(Level.SEVERE, null, ex);
            }
        }
        return "";
    }

    @Override
    public String getAsString(FacesContext facesContext, UIComponent uiComponent, Object value) {

            return value != null ? value.toString() : "";

    }
}


          <p:selectOneMenu value="#{transferenciaEstoqueMB.transferenciaDet.transProdOrigem.prod}"
                                     filter="true" filterMatchMode="contains"
                                     converter="conversorProd"
                                     id="slcProd"
                                     >
                        <f:selectItem itemLabel="Selecione" noSelectionOption="true"/>
                        <f:selectItems value="#{transferenciaEstoqueMB.listProduto}"
                                       var='p'
                                       itemLabel="#{p.cod}-#{p.descricao}"
                                       itemValue="#{p.idComposta}"/>
                        <p:ajax listener="#{transferenciaEstoqueMB.onChangeProd()}"
                                process="@this"  update="@(.transProd)"/>
                    </p:selectOneMenu>