I have a seemingly simple relationship. I have ContentItem with a composite ID (md_id, lang_id), both are type 'long'. I have a ContentBranch object that also has a composite ID (branch_id, lang_id), both are type 'long'. I have an associating table that has three columns (md_id, lang_id, branch_id) and I am having trouble creating the relationship that I want in the mapping file.

Here is branch:

<!-- Branch -->
<class name="com.company.project.Branch" table="mdwfbranch">
<meta attribute="class-description" inherit="false">
This class holds all available metadata branches
</meta>
<jcs-cache usage="read-only"/>
<composite-id>
<key-property name="id" type="long" column="branch_id"/>
<key-property name="langid" type="long" column="lang_id"/>
</composite-id>
<many-to-one name="language" column="lang_id" class="com.company.project.Language" cascade="none" not-null="true" insert="false" update="false"/>
<property name="description" type="string">
<column name="description" length="40" not-null="true" unique="true"/>
</property>
<property name="active" type="boolean">
<column name="active" index="mdWFBranch_idx01" not-null="true"/>
</property>
</class>

Branch works perfectly alone.

ContentItem:

<class name="com.company.project.ContentItem" table="mdcontent">
<meta attribute="class-description" inherit="false">
This class contains the needed metadata information for each studio tip
</meta>
<jcs-cache usage="read-only"/>
<composite-id>
<key-property name="id" type="long" column="md_id"/>
<key-property name="langid" type="long" column="lang_id"/>
</composite-id>

<many-to-one name="level" class="com.company.project.ContentLevel" insert="false" update="false">
<column name="level_id" not-null="true"/>
<column name="lang_id" not-null="true"/>
</many-to-one>

<many-to-one name="type" class="com.company.project.ContentType" insert="false" update="false">
<column name="type_id" not-null="true"/>
<column name="lang_id" not-null="true"/>
</many-to-one>

<set name="branches" table="mdbranchchild" lazy="true">
<key>
<column name="md_id" not-null="true"/>
<column name="lang_id" not-null="true"/>
</key>
<many-to-many class="com.company.project.Branch">
<column name="branch_id" not-null="true"/>
<column name="lang_id" not-null="true"/>
</many-to-many>
</set>

</class>

It throws an exception on the set because "lang_id" is repeated.

I found a solution by adding an additional column to the relational table. I added a 'branch_lang_id" to the table. So, what I have now is a relational table with these fields: md_id, lang_id, branch_id, branch_lang_id

This works, but I have to maintain two columns with exactly the same data. I would never want to link a content item that is English with a Branch that is Japanese. I wanted to use the same column in both composite ID's but Hibernate would not allow it in the mapping file.

Is there any other way that I could have acheived what I wanted without creating the additional column?

I have asked for something similar before: http://forum.hibernate.org/viewtopic.php?t=925446

Maybe, if more people want it, it will be implemented... :)