This situation is documented in the hibernate reference:
Code:
Alternatively, a foreign key with a unique constraint, from Employee to Person, may be expressed as:
<many-to-one name="person" class="Person" column="PERSON_ID" unique="true"/>
And this association may be made bidirectional by adding the following to the Person mapping:
<one-to-one name"employee" class="Employee" property-ref="person"/>
So, for your example, in TableA.hbm.xml
Code:
<one-to-one name="BObject" property-ref="AObject"/>
And in TableB.hbm.xml
Code:
<many-to-one name="AObject" column="tableA_id" unique="true"/>