We added support for ".properties" files in Acceleo in the latest development version (this support appeared for 3.0M1, at the time named 0.9M1). However we realized that this first version of the properties handling left no place for customization/overriding of properties ; no place for internationalization ; and deployment of generation modules as plugins would most likely cause issues with properties lookup. Bug 311045 and bug 311068 have been opened to track these issues.
If you are one of the early adopters that made use of the property support, you'll need to cope with a little change for the M7 build : in the generated class was an "addProperties" method which allowed you to registered the full path to the properties file that was to be loaded. For example if you had a file named "messages.properties" in package "sample" of plugin "org.eclipse.acceleo.sample", you had to register the path "platform://plugin/org.eclipse.acceleo.sample/sample/messages.properties".
You will now have to return a list through the method "getProperties" (well, "addProperties" is still there yet deprecated), and this list will have to contain "sample.messages" (that is,
Likewise, if you had set anything as "generated NOT" in the generated launcher, you will have to manually go through some minor API changes as we ended up creating a common superclass for all launchers. Specifically, launchers now "extends AbstractAcceleoLauncher", and what was once private or protected is now mostly public. This means previously generated launchers that had set any method as "generated NOT" might have to enhance the visibility from private to public. Take note that previously generated launchers that have been built and deployed will not fail and can still be used as is, though enabling re-use of your generator can only be done by letting Acceleo regenerate it (or simply code yourself to take these changes into account).
Sorry about these changes (especially past M6), but we really thought best to remove the bug-prone behavior instead of trying to maintain it since it had never been released in a stable build. The new API should allow for a real use of property files and enhance the re-usability of any generation module.
If you wish to have a look at these changes and cope with them before M7 goes live, they are all accessible in the integration build I201004291415 that went live today (see the download page for the zip or all-in-one update site downloads).
If you have any doubt or questions about these issues, feel free to answer the m2t newsgroup thread I started with a copy of this post.