I think you do not need to set an "id"; for B just use a <component> in the A class hibernate mapping file, and it'll be enough.
like here:
http://www.hibernate.org/hib_docs/v3/re ... entobjects
so you'll have
Code:
<class name="A" table="T1">
<id name="id" column="ID" type="...">
<generator ... /></generator>
</id>
<property name="name" column="NAME" ... />
<component name="Step" class="B" unique="true">
<property name="step" column="STEP" type="..." />
</component>
</class>
thanks for rating this answer!
Maxx