Adventures in Grails

I was recently face with the need to rewrite an entire (ok, 3/4 finished) web application from scratch. The app provided SOAP services for external clients, had integrated search (in both the web interface and WS), restricted user access and search results based on profile and needed to be very scalable. We had previously used AppFuse to build the app, so it was using Spring, Hibernate, Lucene, Compass, Acegi,WebWork, CXF (after upgrading XFire) using WS-Security, etc… I needed to maintain the robustness and scalability of those tools while increasing the flexibility and prototyping efficiency. Enter Grails.

I have been using Groovy to do my scripting tasks for the last 4-5 months. I love it. I can write a script with the same ease and power as I can in Perl or Python and have direct access to my domain model and Hibernate DAOs. Once its working, it is no great leap to wire it up in Spring and have it run on a timer in my app. Groovy alone was enough to get me to give Grails a shot. Once there the near instant ability to create a web UI for CRUD with just three total lines of controller code had me hooked. The fact that plugins for XFire, Acegi and Compass/Lucene already exist make it appear to be the perfect platform for what I need to accomplish. Sure the plugins are young, and I may have to do some work to get some of them to the level I need, but that is the beauty of open source.

I plan to blog my experiences as I put the app together. Stay tuned to see how it goes.

Getting Started

I found a wealth of information to get me started using Grails.

• Grails online Docs http://grails.org/Installation
• Grails podcasts http://grails.org/Grails+Podcast
• Grails screencasts http://grails.org/Grails+Screencasts
• InfoQ’s free ebook http://infoq.com/minibooks/grails

Web Services (XFire)

Once I had an idea of how to start building the app with Grails I figured I would get the Web Services running with the XFire plugin. Using the getting started section of the XFire plugin page I quickly had a simple service up and running.
grails install-plugin xfire
grails create-service Test

Add the expose property to the service.
static expose=['xfire']

and
grails run-app
fire off a test SOAP message and IT WORKS!!!!!
Cool, now I need some data in the DB to see how that looks. Enter it by hand? No, I’ll create a controller and use the web UI! OK, now run the app and fire off a test message….

Pttthhhbbbbb!?!?!?!

Unexpected EOF in prolog at [row,col {unknown-source}]: [1,0]

What the….? Adding a controller breaks the web services? My first wrinkle!
Turns out that you have to pay attention to the “Upgrade to Grails 0.5(URL Mapping)” section on the XFire plugin page too. If you don’t add the following constraint to the Grails URL mapping the controller framework mangles the request.

static mappings = {
          "/$controller/$action?/$id?"{
              constraints {
                        controller(matches:/.*[^(services)].*/)
                  }
          }
}

Thanks to Jason Morris-5 on the Grails mailing list, he worked through the same issue just a few weeks earlier and found the answer.Well, can’t beat an active mailing list. Another plus. All in all a very good experience so far.