Steve just committed a new interface and extension point to Hibernate Core. We can finally plug-in custom Session context management into Hibernate. For those of you who already know getCurrentSession() in Hibernate 3.0, this new extension enables the same without a JTA environment.
I recently spoke at TheServerSideJavaSymposium and at the New England JUG. My presentations, which cover some new ideas implemented in Hibernate 3.0 are now online:
Hibernate 3.0 is the world's most sophisticated ORXM (Object/Relational/XML Mapping) solution. Hibernate3 makes it easier than ever before for Java applications to interact with persistent data, allowing a single definition of the transformation between various in-memory representations of the entity data and the relational schema, even in the case of very complex legacy schemas and schemas for historical data or data with visibility rules. Hibernate3 also provides the most comprehensive object/relational query functionality, with three full-featured query facilities: Hibernate Query Language, the newly enhanced Hibernate Criteria Query API, and enhanced support for queries expressed in the native SQL dialect of the database.
We just released Hibernate 3.0 beta 1. I've no time to list all the many changes since the alpha was released four months ago, let alone everything that is new in Hibernate3, which has been in development for over a year now.
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.
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).
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've seen three or four
ORM tool comparisons in the last three weeks; on some weblogs, on our
forum and I've even been part in several decisions.