Question

I have a simple Java model where a ListHolder holds a List that in turn can hold ListHolder objects:

public class ListHolder {
    private List<ListHolder> list;
}

My approach for a Hibernate mapping file looks like this:

<class name="ListHolder" table="tListHolder">
    <id column="id" type="int">
        <generator class="native"/>
    </id>
    <list name="list" access="field" cascade="all">
        <key column="parent" not-null="true"/>
        <index column="elementIndex"/>
        <one-to-many class="ListHolder" />
    </list>
</class>

When I use the above with Hibernate 3.0, I get the following exception:

Exception in thread "main" org.hibernate.HibernateException: 
Unable to instantiate default tuplizer 
[org.hibernate.tuple.entity.PojoEntityTuplizer]
at org.hibernate.tuple.entity.EntityTuplizerFactory.constructTuplizer(
  EntityTuplizerFactory.java:110)

Am I doing anything wrong in the mapping file? Is there a better way to map Lists that works?

Does it make sense to try the above with a more recent (3.6) Hibernate version?

Answer 1

Upgrading to 3.6 didn’t change anyhting. Adding javassist to the CLASSPATH brought more helpful error messages. It turned out that another member without a setter was the culprit for the stack trace and that the relationship of the List is actually a many-to-many. The following mapping now works without flaws:

<class name="ListHolder" table="tListHolder">
    <id name="id" column="fid" type="long" />
    <property name="name" column="fname" type="string" length="100" />
    <list name="list" access="field" cascade="all">
         <key column="parentId" />
         <index column="elementIndex"/>
         <many-to-many class="ListHolder"/>
    </list>
</class>