Hibernate mutual one-to-one relation

Question

I have two classes Hotsheet and Invoice and one-to-one relation between them. I need to have a property in both classes which will link to each other. Here's my xml mapping of Invoice class.

<hibernate-mapping>
<class name="...Invoice" table="invoices">
    <id name="invoiceId" column="INVOICE_ID"/>

    ...

    <many-to-one
            name="hotsheet"
            column="HOTSHEET">
    </many-to-one>
</class>
</hibernate-mapping>

Invoice has a foreign key that links to its Hotsheet and I also need a property in Hotsheet which will have its Invoice. If Hotsheet could have few invoices I would map it this way:

<hibernate-mapping>
<class name="package.Hotsheet" table="hotsheets">
    <id name="hotsheetId" column="HOTSHEET_ID"/>

    ...

    <bag name="invoices">
        <key column="HOTSHEET"/>
        <one-to-many class="...Invoice"/>
    </bag>
</class>
</hibernate-mapping>

But this was, Hotsheet will have a list which will always contain only one Invoice, while I need a property with Invoice, not list with one Invoice.

Answer 1

You can follow this link for one-to-one mapping in Hibernate. So you hbm files may be as follows:

<hibernate-mapping>
  <class name="...Invoice" table="invoices">
  <id name="invoiceId" column="INVOICE_ID"/>

  ...

  <many-to-one name="hotsheet" class="package.Hotsheet" column="INVOICE_HOTSHEET"  not-null="true" cascade="all" unique="true" />
  </class>
</hibernate-mapping>

<hibernate-mapping>
  <class name="package.Hotsheet" table="hotsheets">
  <id name="hotsheetId" column="HOTSHEET_ID"/>

  ...
  <one-to-one name="invoice" 
    property-ref="hotsheet"/>
</class>
</hibernate-mapping>

Note that to create the one-to-one relationship we use the many-to-one with constraint unique set to true for the column INVOICE_HOTSHEET.

BR.