It is a pretty good book. It was released in September and is already a bit out of date. JRuby & the Ruby world in general seem to move pretty fast.
The topics I liked the best were:
- Nuts & bolts of Java & JRuby integration
- Talk of REXML limitations and the (nice) option to just bang out to the multitude of Java XML APIs should you need extra features
- JRuby & JMX
- JRuby & MOM (Message Oriented Middleware) - ActiveMessaging
After reading it and messing with JRuby a bit, I'm more certain of what I thought in May (ok I didn't say that exactly & I've lost track of Scala - focus on the JVM :) ).
There clearly is a very bright future for Ruby in general & in particular Ruby on the JVM.
What (obviously) makes JRuby + Java so compelling is:
- There is a Java API for *everything*. I hope to stay in Ruby code as much as possible, but it sure is nice knowing that the APIs I have been using for the past 10 years are easily available
- The majority of companies run Java in their data center & are very comfortable deploying to it. Many are also not comfortable adding platforms (e.g., C Ruby)
- The JVM has had a tremendous amount of engineering put into it
- Ruby is a fantastic language that truly is a joy to work with
- Ruby has heaps of momentum & enthusiasm behind it