Hello, I`m new to hibernate and now i`m trying to make a one-to-one mapping. The following are the .hbm.xml codes. Why am I gatting this:
org.hibernate.MappingException: could not instantiate id generator

Parent Class:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.matera.bmf.entity">
<class name="Calendario" table="BF_CALENDARIO">



<id name="idCalendario" column="ID_CALENDARIO" type="long">
<generator class="foreign">
<param name="property">calendarioOuro</param>
</generator>
</id>



<property name="serie" column="SERIE"/>
<property name="quantidadePadrao" column="QTD_PADRAO"/>
<property name="dataVencimento" column="DT_VCTO"/>
<property name="precoExercicio" column="VLR_PRECO_EXERCICIO"/>
<property name="taxaRegistro" column="TAXA_REGISTRO"/>
<property name="emolNormal" column="VLR_EMOL_NORMAL"/>
<property name="emolDaytrade" column="VLR_EMOL_DAYTRADE"/>
<property name="funGaranNormal" column="VLR_FUN_GARAN_NORMAL"/>
<property name="funGaranDaytrade" column="VLR_FUN_GARAN_DAYTRADE"/>
<property name="margemNormal" column="VLR_MARGEM_NORMAL"/>
<property name="margemHedger" column="VLR_MARGEM_HEDGER"/>
<property name="mercAgrMesPresente" column="DT_MERC_AGR_MES_PRESENTE"/>
<property name="mercAgrAvisoEntrega" column="DT_MERC_AGR_AVISO_ENTREGA"/>
<property name="corTermMesPresente" column="DT_COR_TERMO_MES_PRESENTE"/>
<property name="corTermAvisoEntrega" column="DT_COR_TERMO_AVISO_ENTREGA"/>

<many-to-one name="mercadoria"
column="ID_MERCADORIA"
class="Mercadoria"
cascade="all"
lazy="false"/>
<one-to-one name="calendarioFuturo"

class="CalendarioFuturo"
cascade="all"
lazy="false"/>
<one-to-one name="calendarioTermo"

class="CalendarioTermo"
cascade="all"
lazy="false"/>
<one-to-one name="calendarioOpcao"

class="CalendarioOpcao"
cascade="all"
lazy="false"/>
<one-to-one name="calendarioOuro"
constrained="true"
class="CalendarioOuro"
cascade="all"
lazy="false"/>

<many-to-one lazy="false" name="tipoOpcao" cascade="save-update"
column="ID_TIPO_OPCAO_CALENDARIO"
class="TipoOpcao"
unique="true" />
</class>
</hibernate-mapping>



Now the Child Class mapping:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.matera.bmf.entity">
<class name="CalendarioOuro" table="BF_CALENDARIO_OURO">
<id name="idCalendario" column="ID_CALENDARIO" type="long">
<generator class="foreign"/>
</id>
<property name="valorAnterior" column="VLR_ANTERIOR"/>
<property name="valorAtual" column="VLR_ATUAL"/>
<property name="valorUltimo" column="VLR_ULTIMO"/>
<property name="valorMaximo" column="VLR_MAXIMO"/>
<one-to-one name="calendario"
class="Calendario"
cascade="all"
lazy="false"/>
</class>
</hibernate-mapping>

The CalendarioOuro class must have a "non-foreign" id generator. In your case you have both your id generators as foreign which is not possible. What id-generator = foreign means is that the id will be dertived from the primary key of a one-to-one association.

In your case case try:


What this means is that the "id" for Calendario should be assigned by the Persisting class (i.e. before calling "saveXXX" methods).

Hope that helps.