Hello,

I'm relatively new to Hibernate (am actually porting over / abstracting much of my Castor-based code), and i've run into a snag. In Castor, you can query on nested properties such as "where answer.question.survey.id = 1". This dot notation works one level deep with Hibernate (such as "where survey.id = 1"), but seems to die when we go one level deeper.

Is there a way to query on nested properties using the Expression builder?

ex: Expression.eq("answer.question.survey.id", new Long(1));

Any help would be greatly appreciated,
Brian

Are you talking about HQL, or about the Criteria API?

In HQL, you can use path expressions to navigate joins.

In the Criteria API, you cannot (they may only navigate component paths) and this is probably a Good Thing.

If you are just asking how to do joins in the Criteria API, use Criteria.createCriteria(String), or Criteria.createAlias(String, String).

I don't see Criteria.createCriteria(String) or Criteria.createAlias(String, String) in the Hibernate 2.0 API... am I missing it?

Hibernate 2.1 beta 4

Excellent...

Keep up the great work on your fantastic product!

Welcome...

I did the same migration (from Castor to Hibernate) about a year ago. You will not regret it. :)

Well, i'm trying to keep my apps "persistence layer agnostic" by abstracting out all reading/writing functionality... The problem is that there are so many features that Hibernate has that Castor doesn't have, that makes me wonder if it's even worth trying to treat the two as "equals".

Question:
The API docs for Hibernate 2.1 beta 4 are a bit sparse regarding Criteria.createAlias(String, String) and Criteria.createCriteria(String). If I wanted to implement a join (nested property lookup), what would the code look like?

For example, what would I translate something like:
Expression.eq("survey.question.answer.id", new Long(1)) to using Criteria.createAlias or createCriteria?

My interface for my "generic" querying mechanism has a function:
addWhereClause(String property, String comparison, Object value)

This works pretty directly in Castor. I have to translate these into the appropriate Expression.eq...etc statements in Hibernate (no big deal). I really don't want to use HQL, since it's not as OO as the Criteria API. I wrote a translator for Castor's OQL. It was a ton of work, and I don't want to have to go through that again :)