Hi friends. I was using a Set but now due to a widget restriction, I need to use a list.a a sample of my mapping file using A SET and a List are as follows. Can someone help me to place the list index. I am getting some confusion.

**Attribute Mapping File using Set**
?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Dec 16, 2010 5:25:09 AM by Hibernate Tools 3.4.0.Beta1 -->
<hibernate-mapping>
<class name="h.Attribute" table="ATTRIBUTE">
<id name="AttributeId" type="long">
<column name="ATTRIBUTEID" />
<generator class="native" />
</id>
<property name="AttributeName" type="java.lang.String">
<column name="ATTRIBUTENAME" />
</property>
<set name="Options" table="ATTRIBUTEOPTION" inverse="false" cascade="all" lazy="true">
<key>
<column name="ATTRIBUTEID" />
</key>
<one-to-many class="h.AttributeOption" />
</set>
</class>
</hibernate-mapping>



**Category Mapping File using Set**
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Dec 16, 2010 8:37:02 AM by Hibernate Tools 3.4.0.Beta1 -->
<hibernate-mapping>
<class name="h.Category" table="CATEGORY">
<id name="CategoryId" type="long">
<column name="CATEGORYID" />
<generator class="native" />
</id>
<property name="CategoryName" type="java.lang.String">
<column name="CATEGORYNAME" />
</property>

<many-to-one name="ParentCategory" class="h.Category">
<column name="PARENT_CATEGORY_ID" />
</many-to-one>

<set name="SubCategory" lazy="true" cascade="all-delete-orphan" inverse="true">
<key>
<column name="PARENT_CATEGORY_ID" />
</key>
<one-to-many class="h.Category" />
</set>


Category Mapping File using list without the list index

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Dec 17, 2010 2:10:50 AM by Hibernate Tools 3.4.0.Beta1 -->
<hibernate-mapping>
<class name="h.Category" table="CATEGORY">
<id name="CategoryId" type="long">
<column name="CATEGORYID" />
<generator class="assigned" />
</id>
<property name="CategoryName" type="java.lang.String">
<column name="CATEGORYNAME" />
</property>
<many-to-one name="ParentCategory" class="h.Category" fetch="join">
<column name="PARENTCATEGORY" />
</many-to-one>
<list name="SubCategory" inverse="false" table="CATEGORY" lazy="true">
<key>
<column name="CATEGORYID" />
</key>
<list-index></list-index>
<one-to-many class="h.Category" />
</list>
<list name="AllAttributes" inverse="false" table="ATTRIBUTE" lazy="true" cascade="all">
<key>
<column name="CATEGORYID" />
</key>
<list-index></list-index>
<one-to-many class="h.Attribute" />
</list>
</class>
</hibernate-mapping>

Attribute Mapping File using list with not list index

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Dec 17, 2010 2:10:50 AM by Hibernate Tools 3.4.0.Beta1 -->
<hibernate-mapping>
<class name="h.Attribute" table="ATTRIBUTE">
<id name="AttributeId" type="long">
<column name="ATTRIBUTEID" />
<generator class="assigned" />
</id>
<property name="AttributeName" type="java.lang.String">
<column name="ATTRIBUTENAME" />
</property>
<list name="Options" inverse="false" table="ATTRIBUTEOPTION" lazy="true" cascade="all">
<key>
<column name="ATTRIBUTEID" />
</key>
<list-index></list-index>
<one-to-many class="h.AttributeOption" />
</list>
</class>
</hibernate-mapping>


<set name="AllAttributes" table="ATTRIBUTE" inverse="false" lazy="true" cascade="all">
<key>
<column name="CATEGORYID" />
</key>
<one-to-many class="h.Attribute" />
</set>

</class>
</hibernate-mapping>

I am trying to place <list-index column="idx"/>
Exception in thread "main" org.hibernate.HibernateException: null index column for collection: h.Category.AllAttributes
at org.hibernate.persister.collection.AbstractCollectionPersister.readIndex(AbstractCollectionPersister.java:598)
at org.hibernate.collection.PersistentList.readFrom(PersistentList.java:297)
at org.hibernate.loader.Loader.readCollectionElement(Loader.java:569)
at org.hibernate.loader.Loader.readCollectionElements(Loader.java:344)
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:299)
at org.hibernate.loader.Loader.doQuery(Loader.java:384)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:203)
at org.hibernate.loader.Loader.loadCollection(Loader.java:1344)
at org.hibernate.loader.collection.OneToManyLoader.initialize(OneToManyLoader.java:106)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:484)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:60)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1346)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:170)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:47)
at org.hibernate.collection.PersistentList.size(PersistentList.java:81)
at h.FirstExample.main(FirstExample.java:54)