7.2.2. One-to-one
A unidirectional one-to-one association on a foreign key is almost identical. The only difference is the column unique constraint.
<class name="Person">
<id name="id" column="personId">
<generator class="native"/>
</id>
<many-to-one name="address"
column="addressId"
unique="true"
not-null="true"/>
</class>
<class name="Address">
<id name="id" column="addressId">
<generator class="native"/>
</id>
</class>create table Person ( personId bigint not null primary key, addressId bigint not null unique ) create table Address ( addressId bigint not null primary key )
A unidirectional one-to-one association on a primary key usually uses a special id generator In this example, however, we have reversed the direction of the association:
<class name="Person">
<id name="id" column="personId">
<generator class="native"/>
</id>
</class>
<class name="Address">
<id name="id" column="personId">
<generator class="foreign">
<param name="property">person</param>
</generator>
</id>
<one-to-one name="person" constrained="true"/>
</class>create table Person ( personId bigint not null primary key ) create table Address ( personId bigint not null primary key )
