jpa-nullrelation/src/main/resources/META-INF/orm.xml

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm" version="1.0">
  <entity name="ABean" class="org.superbiz.nullrelation.ABean">
    <table name="ABEAN"/>
    <attributes>
      <id name="id">
        <column name="ID"/>
      </id>
      <basic name="value">
        <column name="VALUE"/>
      </basic>
      <basic name="name">
        <column name="NAME"/>
      </basic>
      <one-to-one name="b" mapped-by="a"/>
      <one-to-one name="Z" mapped-by="a"/>
    </attributes>
  </entity>
  <entity name="BBean" class="org.superbiz.nullrelation.BBean">
    <table name="BBEAN"/>
    <attributes>
      <id name="id">
        <column name="ID"/>
      </id>
      <basic name="value">
        <column name="VALUE"/>
      </basic>
      <basic name="name">
        <column name="NAME"/>
      </basic>
      <one-to-one name="C" mapped-by="b"/>
      <one-to-one name="a">
        <join-column referenced-column-name="ID" name="FK_FOR_ABEAN"/>
      </one-to-one>
    </attributes>
  </entity>
  <entity name="CBean" class="org.superbiz.nullrelation.CBean">
    <table name="CBEAN"/>
    <attributes>
      <id name="id">
        <column name="ID"/>
      </id>
      <basic name="value">
        <column name="VALUE"/>
      </basic>
      <basic name="name">
        <column name="NAME"/>
      </basic>
      <one-to-one name="b">
        <join-column referenced-column-name="ID" name="FK_FOR_BBEAN"/>
      </one-to-one>
      <one-to-one name="a">
        <join-column referenced-column-name="ID" name="FK_FOR_ABEAN"/>
      </one-to-one>
    </attributes>
  </entity>
</entity-mappings>