Thursday, February 16, 2012

I will defeat you Grails config loader!

by Richard Vowles

As part of the way we do thing, we wanted to use properties files rather than the plain config.groovy - and thats pretty normal - Grails documentation even gives you a mechanism to load in extra config.

Ideally for us, this could be configured outside of Grails - through some Spring mechanism rather than having to modify the Grails config for every app, but its ok - it has worked. Until today. Today I hit the bug in Groovy where the Properties -> ConfigObject via ConfigSlurper started giving weird results. I had these lines

grails.mail.host = localhost
grails.mail.port = 5000

and i was getting

grails.mail.host = localhost
grails.'mail.port' = 5000
grails.mail.port = [:]

which turns out to be a peculiarity of how Groovy loads the file - and there are quite a few bugs around this on the Groovy bug parade - back since 1.6 (and unclosed).

So how to get Grails to load a properties file in my own fashion? Well thats where the fun started. Turns out that Grails hard codes in its scripts the creation of the DefaultGrailsApplication, which in turn has hard coded the ConfigurationHelper. Neither of these were overrideable or extendable without forking Grails 1.3.7. So one of the things we had been doing was using static methods on our class - and in the end, this turned out to be our saviour - that and Groovy's MOP.

As there were lots of parse methods already, I added a methodMissing to detect for a request for a parse with our class and then passed it onto a method of my choosing that would turn the tree into something more resembling common sense.

That seemed to fix it - so if you have the same problem with broken properties loader when using Grails, that approach worked for me.
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