For the most part, I did not have to do anything overly special to work with the AS400. DB2/400 supports all the features that Grails (via Hibernate) uses. The biggest issue was working with tables that have composite keys. Note that, although Grails has facilities for working with composite keys, rather than keying the required GORM code, I used the Systemi Grails Domain Plugin. This plugin has a script that takes an AS400 table and generates the Grails domain class. I have used that plugin (which I wrote with help from Mike Brown) to generate hundreds of Grails domain classes for tables on about a dozen different AS400s (all at different companies.) You can read more about the tool in my article Rapid IBM i Web Dev with Open Source Tools (note that article will require a web subscription to www.systeminetwork.)
KETTLER USA was deployed to a 64-bit Windows server that is running on Tomcat. The Tomcat server is behind a firewall with an Apache server running outside the firewall as a proxy server. The Tomcat server is able to connect to the AS400 via JDBC. The Tomcat server can only be accessed from the Apache server so it is a secure AS400 connection.
Most of the application is written using Grails domain classes to access DB2/400, but there are some points where the application does direct calls to RPG via JDBC stored procedures or indirect RPG calls via AS400 data queues. I will be elaborating on this in a future post.
I've been coding 12x7 for so many months getting the Kettler retail site up that I've forgotten some of the slick things that I was able to do with Grails (where coding the solution in Java would have been far more difficult.) But one thing, off the top of my head, that I loved being able to do was to put the Grails domain classes in their own Grails project and pull that project into the UI project as a Grails plugin. The reason why I needed to do this was that I had written a Business-to-business Grails application for Kettler last year. And the retail application used many of the same Grails domain classes. As they say "there shall be no duplicate code." And I certainly didn't want to maintain the 85 domain classes required for Kettler in two places. With one of the more recent versions of Grails (we are on 1.3.5 now) Grails made using your own project Grails plugins very easy. Instead of having to generate a Grails zip archive and import it to the project that requires that plugin -- everytime that supporting project is changed -- you simply put a reference to that project in your grails-app/conf/BuildConfig.groovy:
grails.plugin.location.'shared-domain-plugin' = "../SharedDomainPlugin"
Again, I will be added more Grails400 posts in the future.