Question

I have two tables: foo (primary key: foo_id) and foo_entry (primary key: foo_entry_id; foreign key: foo_id).

Below is my Hibernate config.
My problem is, when I call getAttributes() on the FooModel class, I end up with a list of a little over one million null objects. (foo table has ~200 rows, foo_entry has ~10,000).

I’m new to Hibernate and suspect I am just overlooking or am just not understanding something very, very basic. Any help appreciated!

<hibernate-mapping package="com.blah.www">
  <class name="FooModel" table="foo">
    <id name="fooId" column="foo_id"></id>

    <list name="attributes" table="foo_entry">
      <key column="foo_id" />
      <index column="entry_id" />
      <one-to-many class="FooEntryModel" />
    </list>
  </class>
</hibernate-mapping>

<hibernate-mapping package="com.blah.www">
  <class name="FooEntryModel" table="foo_entry">
    <id name="fooEntryId" column="foo_entry_id">
      <generator class="native" />
    </id>

    <property name="fooId"      type="int"       column="foo_id"      /> 
    <property name="attrName"   type="string"    column="attr_name"   />
    <property name="attrValue"  type="string"    column="attr_value"  />
    <property name="startDate"  type="timestamp" column="start_date"  /> 
    <property name="endDate"    type="timestamp" column="end_date"    />
  </class> 
</hibernate-mapping>

Answer 1

Sigh…

This turned out to have a very logical (and very subtle) explanation.
I had misunderstood and hijacked the semantics of the <index> (also known as <list-index>) tag within <list>. Namely, given:

<list name="attributes">
    <key column="foo_id" />
    <index column="some_integer_value" />
    <one-to-many class="FooEntryModel" />
</list>

… I thought was referring to the attribute by which you want to order the list. In fact, it refers to an attribute whose value denotes at what index position within the list to insert the overall object. It’s meant to be a placeholder attribute, maintained and used entirely by Hibernate.

The value of the “some_integer_value” to which I was mapping varied in my test data. Sometimes the value was less than a 100. Sometimes it was greater than a million.

Thus, upon mapping just one row where “some_integer_value” == e.g. 100,001, Hibernate would create a list with that object inserted in the 100,001st position. Every list member preceding it, naturally, would be null.