Upgrading from Grails 1.0.3 to 1.3.5

Question

I've just inherited an application written in Grails (version 1.0.3) and would like to upgrade it to the newest release (version 1.3.5).

I can't seem to find a reference that enumerates the differences between the two versions. I know there is the "grails upgrade" command - but is this the best option given the large differences in versions.

I have a similar question that I asked today as well for upgrading the version of Groovy, and the sntactical differences to be aware of (between version 1.3.5 and 1.7.5) - but I thought it may be best to separate the two questions to focus on each.

Many thanks,

~Aki

Answer 1

Things have changed quite a bit since 1.0.3, and unfortunately grails upgrade isn't going to do much for you.

Two significant changes that come to mind are that there was a bug in 1.0.3 and previous where 1-many and many-to-many collections (hasMany/belongsTo) were supposed to be lazy-loaded but weren't. This was fixed in 1.0.4 and several users found that they were relying on the behavior and saw issues. Most people didn't, and just saw a significant performance boost. So watch out for lazy loading exceptions.

Another thing that changed is that plugins are no longer in the root of the project in the 'plugins' folder but are now stored under your $HOME/.grails folder. If you've checked the plugins into source control (and especially if you've made any changes) then you can revert to 1.0.x behavior by adding a property to BuildConfig.groovy (a new file that was introduced in 1.1):

grails.project.plugins.dir = 'plugins'

I described my process for upgrading plugins and apps here: How to install Grails plugin from source code? - it's about a plugin project but the same goes for app upgrades.

The log4j configuration changed from one that's properties-based to a DSL. This means that if you leep your config settings from Config.groovy the log4j behavior will be the default, so you'll need to convert that.

Another change that isn't required but should be considered is that Ivy jar file resolution from Maven repos is now preferred over putting jar files in the lib directory. You can still put them in the lib dir, but it's more DRY to have Ivy download them once.

You'll probably also find that some of the plugins you have don't work in 1.3, so there might be some migration work there.

There are two recent books that cover Grails 1.2/1.3, "Grails: A Quick-Start Guide": http://www.amazon.com/dp/1934356468/ and "Getting Started with Grails, 2nd ed": http://www.infoq.com/minibooks/grails-getting-started - you should probably check those out since they're the most current Grails books.

Overall it shouldn't be that bad, as long as you don't try to upgrade in-place. Use the approach I described in the other post I referenced, i.e. create empty apps and diff files to see what changed (basically a 3-way diff).

Answer 2

The newest release is 1.3.6 (as of Dec 15). You can get a list of changes from the Release Notes of each release. Also, the upgrading from previous versions link the documentation is a good source of changes.