I gotta preface this post by saying that we are very skeptical of the idea that Java is the right place to do processing that works with data in bulk. By extension, ORM is probably not an especially appropriate way to do batch processing. We think that most databases offer excellent solutions in this area: stored procedure support, and various tools for import and export. Because of this, we've neglected to properly explain to people how to use Hibernate for batch processing if they really feel they /have/ to do it in Java. At some point, we have to swallow our pride, and accept that lots of people are actually doing this, and make sure they are doing it the Right Way.
One of the joys of working on an open source project with commercial competitors is having to implement features that our users simply don't ask for, and probably won't use in practice, just because those competitors try to spin their useless features as a competitive advantage. We realized ages ago that it's really hard to tell people that they don't need and shouldn't use a feature if you don't have it.
We were doing some work with a customer with a very large project recently, and they were concerned about traceability of the SQL issued by Hibernate. Their problem is one that I guess is common: suppose I see something wong in the Hibernate log (say, some N+1 selects problem), how do I know which of my business classes is producing this? All I've got in the Hibernate log is org.hibernate.SQL, line 224 as the source of the log message!
Hibernate3 is now ready for a public test, go get it! It has all (well almost all) features we'll ever need for object/relational mapping, and if it doesn't have it, it's easy to subclass, extend, and implement.
There's been a certain amount of noise recently surrounding simple JDBC frameworks
like iBATIS. I've liked the idea of iBATIS myself, for use in applications which
don't need an object-oriented domain model, and don't work with deep graphs of
associated entities in a single transaction. A JDBC framework also makes good sense
if you are working with some kind of
insane legacy database; ORM solutions tend
to assume that associations are represented as nice clean foreign keys with proper
referential integrity constraints (Hibernate3 much less so than Hibernate 2.x).
Just had an interesting discussion on email@example.com, started by David Cherryhomes, which saw me stupidly insistingthat something can't be done when in fact, now that I think about it, /I realize I've actually done it before/, and that even the Hibernate AdminApp example uses this pattern!
Another major change in Hibernate3 is the evolution to use an event and listener paradigm as its core processing model. This allows very fine-grained hooks into Hibernate internal processing in response to external, application initiated requests. It even allows customization or complete over-riding of how Hibernate reacts to these requests. It really serves as an expansion of what Hibernate tried to acheive though the earlier Interceptor, Lifecycle, and Validatable interafaces.
Hibernate3 adds the ability to pre-define filter criteria and attach those filters at both a class and a collection level. What's a
pre-defined filter criteria? Well, it's the ability to define a limit clause very similiar to the existing
where attribute available on the class and various collection elements. Except these filter conditions can be parameterized! The application can then make the decision at runtime whether given filters should be enabled and what their parameter values should be.
I just cleaned up some of my files and found this snapshot in one of my folders. I made it two weeks ago, as I finally had time to install Oracle 10g. I remember how I was shaking my head in desperation as I realized what they had done. Let me explain.
Simple is a seductive notion. We all want to make things simple. But when we talk about software,
simple could mean at least two different things.