Complete database export to JSON / XML

We would like to be able to export our entire database as a modified JSON or an XML file for students and researchers to work on. I found this forum item about adding output formats: but I can't seem to get it to work. Is it still up-to-date for Omeka 2.1? And when I get it to work, would it be possible to somehow use it for exporting an entire collection?

That example is for Omeka 1.x. The general principles are the same, but there's just a lot of renaming for 2.x. For example, define_action_context became just <a href="">action_context</a>.

The function names are also different, following the same changes needed for views elsewhere in the move from 1.x to 2.x

That said, if you are using 2.1 you might want to use the API and an external script to grab the data you want, especially since the API is already giving you JSON.