hibernate messages … nice and unhelpful

One of the reasons why I recommend Tapestry as a web framework is the helpfulness of its error messages. Hibernate is just the opposite.

Current annoying hibernate error message :”Null index column for collection” when trying to examine a previously saved collection.

This seems to be caused by a mysterious IDX column on the class that is to be placed into the map. This column is null for whatever reason. Inserts would succeed but examining the collection would fail.

It turns out this was caused because I was missing a column attribute in the map-key element.

I had this:

<map-key type="long"/>

not this:

<map-key type="long" column="ID"/>