Hibernate version:
2.1.8

Mapping documents:
<class name="Packet" table="packet">
<many-to-one name="category" class="StandardCategories" column="REQ_CATEGORY_ID" not-null="false" />
</class>

So this criteria method:

List l = session.createCriteria(Packet.class).getList();

With the criteria query it only does a join of Packet and StandardCategories.

But since the property category is allowed to be null, to get all packets & their categories you actually need to do a left outer join, and not a regular outer join.

Just a suggestion.