Ruby 1.8.x has the following behavior:
JRuby instead gives the following:
The problem is that IOError is thrown in JRuby while Errno::ENOENT in Ruby MRI.
I found this problem while using Radiant 0.8.1 which has rack-cache on board.
Rack-Cache rescues only Errno::ENOENT and therefore fails to run Radiant.
Here is the code for rack-cache (GEM_HOME\gems\radiant-0.8.1\vendor\rack-cache\lib\rack\cache\metastore.rb):
I'll write a spec and apply a patch soon.