Install in Eclipse as a plugin.

In Eclipse:

Window > Show View > Other ... and choose "Ruby Output"

That brings up a view that shows the current selection run through a filter defined in ${the root of your workspace}/ruby_filter.rb.  A sample ruby_filter.rb is provided
that runs the current selection through and html-escape filter.

The Ruby Output window has a single menu item to reload the filter.  Select that menu item to pick up any changes you make to ruby_filter.

A built version is available from http://jrubyeclipseplugin.s3.amazonaws.com/JrubyEclipsePlugin_1.0.1.jar?AWSAccessKeyId=1XAFRSJH5JTMXX7MFP82&Expires=1403023422&Signature=s2BCVdZkl2IF6TBsCYfqDF7pwiE%3D
Just copy that file into your Eclipse dropins directory.