<?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="org.hibernate.parentChild">
    <class name="Parent">
        <id name="id" column="PARENT_ID">
            <generator class="increment"/>
        </id>

      <version name="version" type="long" />

        <property name="type"/>

        <set name="children" lazy="true" cascade="all" >
            <key column="parent_id" not-null="true"/>
            <one-to-many class="Child"/>
        </set>
    </class>

    <class name="Child">
        <id name="id" column="CHILD_ID">
            <generator class="increment"/>
        </id>

        <many-to-one name="user" column="USER_ID" class="Usr" cascade="all" />
    </class>
   
   <class name="Usr" table="USR">
        <id name="id" column="USER_ID">
            <generator class="increment"/>
        </id>
   
      <property name="firstName" type="string" column="firstName" not-null="true"/>
   
      <property name="lastName" type="string" column="lastName" not-null="false"/>
   </class>
      
</hibernate-mapping>