I am developing a plugin which is used to load the model of SU to xml file. In my Myplugin.rb file, the lib under Ruby193\lib\ruby\1.9.1\rexml is used, i am sure that my Myplugin.rb can work correctly in RubyMine IDE, however, when starting SU 8.0 to load plugin, error occurs caused by failing to load 'rexml/document', how to solve it? thanks.

Any help is appreciated.

Myplugin.rb:

require 'rexml/document'
require 'rexml/text'
require 'entities'
include REXML