<hibernate-mapping package="com.nyker.test.hibernate">
  <class name="Item" table="ITEMS">
    <id name="id" column="ITEM_ID" type="long">
      <generator class="increment"/>
    </id>
    <property name="name"/>
   <set name="bids" cascade="all">
      <key column="ITEM_ID"/>
      <one-to-many class="Bid"/>
   </set>
  </class>
</hibernate-mapping>

<hibernate-mapping package="com.nyker.test.hibernate">
  <class name="Bid" table="BIDS">
    <id name="id" column="BID_ID" type="long">
      <generator class="increment"/>
    </id>
    <property name="amount"/>
  </class>
</hibernate-mapping>

Item item = (Item)session.load(Item.class,new Long(1L));
Bid bid1 = new Bid(144.22);
item.getBids().add(bid1);