<class name="A">
<id name="id" type="int" column="ID"/>
<bag table="AB" lazy="true" inverse="true" name="ListB">
<key column="A_ID"/>
<many-to-many foreign-key="FK_B_ID" column="B_ID" class="B"/>
</bag>
</class>

<class name="B">
<id name="id" type="int" column="ID"/>
<bag table="AB" lazy="true" inverse="true" name="ListA">
<key column="B_ID"/>
<many-to-many foreign-key="FK_A_ID" column="A_ID" class="A"/>
</bag>
</class>

create table AB (
        B_ID number(10,0) not null,
        A_ID number(10,0) not null
);

alter table AB
  add constraint FK_B_ID
  foreign key (B_ID)
  references B;

alter table AB
  add constraint FK_A_ID
  foreign key (A_ID)
  references A;