Go to see Grails, learn about Hibernate

Today I finally got to see the two Grails presentations by Jason Rudolph at No Fluff, Just Stuff. It’s not really an exaggeration to say I decided to attend the conference largely because I knew he’d be there. I like the NFJS conferences, but since I’m a one-person company, the “budget” for the conference comes right out of my pocket. I have to really want to go. Not only that, but for the past two years I’ve attended during the March session. It feels like a bit of a luxury to go twice in a given year, especially when many of the presentations in the fall overlap those from the spring.

But Jason was going to be there, and not only is he a real expert, he’s also a big part of the reason I’m involved with Groovy and Grails in the first place. I blogged about it a long time ago, but about a year ago I happened to be teaching a Spring class in Philadelphia. I happened to notice that the local Spring users group was hosting Jason, talking about this Grails thing I’d only heard about.

At the time I’d gone through my burst of enthusiasm and subsequent disappointment about Ruby on Rails. By that summer I’d come to the conclusion that Ruby was just too much and too different for me to make for a practical transition, not to mention the fact that I knew I wasn’t going to be able to follow their conventions and that was going to be a problem. Still, spending all that time digging into both Ruby and Rails taught me a ton. That was the first I’d heard about closures, for example. I also finally saw the power of a dynamic language, which ironically made me appreciate JavaScript for the first time, just in time for the Ajax revolution.

I guess you could say I was the perfect audience for Jason’s presentation. The fact that I could see all the Rails-like productivity gains and still be able to leverage all my Java experience was worth diamonds to me.

Today, he gave that introductory talk again, and followed up with a more advanced discussion of domain modeling with GORM, Grail’s Object-Relational Mapping framework. The introductory part was a nice refresher, but I was familiar with most of that material.

The advanced talk was very interesting, however. I needed to see how to work with an existing database schema, because that’s real life (despite what the Rails people seem to think). I knew in principle that since Grails just uses Hibernate under the hood, you could just fall back to Hibernate mappings to do whatever you needed. I’d never actually seen that in action, though.

But here was the surprising part. At one point Jason asked the audience if anyone had used the Hibernate Tools project to reverse engineer a database schema. I said I had, and I thought I had, but apparently I really missed the boat on that one.

I’ve tried the reverse engineering process inside an IDE. I originally tried it with MyEclipse, then I tried JBoss IDE. In both cases I felt like the wizard generated as much work for me as just writing the mapping files myself. I never seemed to get the hang of them. I hated seeing Java classes show up that had attributes like “userses” due to some naming convention. Since MyEclipse had content assist on the XML mapping files, it felt easier for me to just write the raw XML.

What Jason showed, however, was an intermediate step that hadn’t occurred to me. He didn’t go from the database schema all the way to the Java classes, which the wizards wanted me to do. Instead he used an Ant build to generate just the Hibernate mapping files and then edited them to suit his domain classes.

Imagine the sound of a light finally dawning. Here’s clue: Star Trek: the Original Series, first season episode “What Are Little Girls Made Of?”, quote by Ruk, the android left by the Old Ones:

“THAT was the equation! Existence! Survival … must … outweigh programming!”

In other words, I get it now.

I tried it with one of my own database schemas this evening, and of course it worked like a charm. I certainly don’t mind editing the resulting XML mapping files, and, even better, I can recommend the practice for clients who have dozens or hundreds of tables.

Thanks, Jason. 🙂 Now I can get back to really learning the framework.

One response to “Go to see Grails, learn about Hibernate”

  1. Hi Ken,
    Thanks for all the kind words. It’s always great to hear that people got some real honest-to-goodness value out of a presentation. 🙂

    For those folks that couldn’t make it to NFJS this time around, the Hibernate tools scripts are available for download. (Once you open the ZIP file, the Hibernate tools are located in gorm/hbm2java. Be sure to check out the README for all the details.)

    It was Raffaele Castagno who originally turned me on to the Hibernate tools, and I’m sure glad he did. He also provided the original draft of the ant script included in the ZIP, and it’s definitely saved me quite a bit of time.


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