How do Rails and Jruby relate?

Question

Background: I have a java library that is accessed by many developers - usually via java. However, a few devs hope to access this via a Ruby API. I am gravitating in the direction of Jruby in order to implement a Java-Ruby API.

Questions:

1. My main concern is that these developers will not be able to utilize the API in their current, Ruby on Rails development framework; but instead will have to operate within Jruby's rails environment. Is this going to be the case?

2. Perhaps I'm missing a connection between Jruby and Ruby on Rails. But it seems that you can either work in Rails, or work in Jruby's rails - are these technically two different development environments?

I would really appreciate any light someone could shed on this..

Edit: Forcing developers (actually clients to be more specific) to make large changes to their projects in order to accomodate for this API is not really an option. So, if their Rails apps would have to be converted to Jruby on Rails apps, then perhaps someone could offer yet another alternative for me (other than Jruby)?

Answer 1

You might find the answers to a similar question helpful. Depending on your application it may be possible to seamlessly port your RoR app to run on JRuby subject to the caveats noted in that answer. But you'd want to be sure that the benefits of doing so balanced the effort and potential risks.

Alternatively you might consider making these Java library facilities available to your MRI Rails app as an internal web service (which could be Rails or Sinatra or similar) built on JRuby. That's way you would decouple the elements and de-risk the project. If you subsequently were comfortable with that working you might then consider collapsing them back together, all under JRuby-on-Rails if that made sense.

UPDATE: Adding more detail at questioners request

As I'm not familiar with what your application or Java libraries do this will be somewhat abstract but I trust you can fill in the blanks to suit your needs.

It seems that full porting of your Rails apps to run on Jruby is not feasible. Fine. So one idea would be to expose your Java library as a web service (e.g. RESTful) to your RoR application. Let's call this thing JLS. In this case it would run as a Java or Jruby network service, listening for requests, call into the library and send back responses (general waving of hands here but you get the idea).

Depending on what your developers are more comfortable with you can create JLS in Java running a Servlet container maybe. Or you could develop JLS in Ruby, running on Jruby (binding to your Java library) and use a framework like Rails or Sinatra to implement it.

On the RoR side, assuming you've made JLS RESTful (and I don't know if that's even appropriate in your case), you can use the ActiveResource facility for communicating with JLS.

In summary the RoR app and JLS run in separate memory spaces (maybe even different hosts). Each can be developed somewhat independently (with RESTful interface agreement of course) and your RoR app does not need to be disrupted or put at risk.

This suggested option comes with tons of small print but I hope you get the general idea.

Answer 2

First, I should mention that Ruby on Rails is simply Ruby code, and the same code can run in the JRuby environment (on the JVM) or the MRI (written in C) runtime.

However, only JRuby can load Java classes and use a Java API. Asking your clients to switch their deployment environment to JRuby may not be feasible, but if you can set up a service in Java that speaks XML or JSON then they will be able to easily use it from Rails.