I have a one-to-many self association that was working fine as TreeSet with sort=natural. I decided to switch to using List but Hibernate keeps complaining about "null index column for collection." Here is my mapping (Note the set is commented out but was working fine for me.)

<class name="CategoryImpl" table="CATEGORY">
<id name="id">
<generator class="native"/>
</id>
<property name="name" type="text"/>
<list name="childCategories"
table="CATEGORY"
inverse="true"
cascade="all">
<key column="PARENT_CATEGORY_ID"/>
<index column="SEQUENCE_COL"/>
<one-to-many class="CategoryImpl"/>
</list>
<!--
<set name="childCategories"
table="category"
sort="natural"
inverse="true"
cascade="all">
<key column="PARENT_CATEGORY_ID"/>
<one-to-many class="CategoryImpl"/>
</set>
-->
<many-to-one
name="parentCategory"
column="PARENT_CATEGORY_ID"
class="CategoryImpl"/>
</class>

Any help would be greatly appreciated. I've tried looking everywhere but I can't seem to find anything specific to a *self* association.

TIA.

I was able to stop the error by adding a sequence to my CategoryImpl class and mapping it as follows:

<property name="sequence" column="SEQUENCE_COL"/>

I had actually tried this earlier but my IDE was not picking up the new mapping file during testing (GRRR.)

Anyways, there is still a problem b/c the child categories are not being stored in the order that they are added to the list. Is this because of the inverse=true on the many end?