JRuby - How Java and Ruby meet on the JVM, PolyConf 2015

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JRuby How Java and Ruby meet on the JVM Alissa Bonas @ PolyConf 2015

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What

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● An implementation of the Ruby programming language atop the JVM ● Written in Java What is JRuby

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JRuby project ● Free and open source software ● http://jruby.org/ ● https://github.com/jruby/jruby

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Some JRuby facts ● Exists since 2001 ● Can run Ruby on Rails apps since 2006 ● Tightly integrated with Java

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Versions support ● Jruby 1.7.x ○ Supports Ruby 1.9.3 ○ Experimental Ruby 2.0 support ● Jruby 9.0.0.0 - in the works ○ Supports Ruby 2.2

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Why

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Reasons to use JRuby ● Integrate Java and Ruby projects ● Enjoy libraries in both languages ● Bonus ○ Multithreading ○ Packaging

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Packaging ● Simple deployment/packaging ● Creating a standard war file

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Multithreading ● Green threads vs native threads ○ GIL (global interpreter lock) ● One process instead of multiple

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Things to consider ● Native C extensions ● Slower startup

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How

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● RVM ● Rbenv ● Download and extract ● Packaged for various OS Install JRuby

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Install JRuby with RVM ● Fast and easy ● Quick switch between several Rubies

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Managing Rubies with RVM

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Ruby versions flavors

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JRuby in action

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Java Calling Ruby ● Eval of Ruby code ● Sharing variables with a Ruby script ● Reading the return value

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Java Calling Ruby ● JRuby Embed (aka Red Bridge) ○ Embed core ○ JSR 223 - Java’s scripting engine ○ BSF (Bean Scripting Framework) ● No need to compile Ruby into bytecode

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JRuby Embed core ● Add jruby.jar to your Java project ● specify JRUBY_HOME ○ needed if JRuby installed via RVM

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Ruby script example # GET http://10.35.0.23:8080/api require ‘net/http’ endpoint = URI::HTTP.build(:host => @host, :port => @port) endpoint.path = ‘/api’ request = Net::HTTP::Get.new(endpoint.to_s) resp = Net::HTTP.start(endpoint.host, endpoint.port) { | http | http.request(request) } resp.body

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Java calling Ruby example

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Output { "versions": [ "v1beta3", "v1" ] }

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require ‘java’ java_import java.lang.System jruby_home = System.getProperties["jruby.home"] puts jruby_home ------------------------------------------------------------ Output: /home/abonas/.rvm/rubies/jruby-1.7.20 Ruby Calling Java

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Example of Rails with JRuby ● Open source Java project - Spago BI ● Several Java reports engines ● Adding a Ruby on Rails reports engine

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Reports Engine 1 Reports Engine 2 Reports Engine 3 UI Reports Engine 4 http /engine1 http /engine2 http /engine3 http /engine4 SOA Tomcat SOA SOA SOA SOA

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Preparation steps ● Use JDBC database drivers ● Package the application ● Deploy

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Database drivers ● JDBC drivers ● Specify them in Gemfile ● Specify them in config/database.yml

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Packaging

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Packaging ● Use Warbler ● Create a .war file ● Flexible configuration possibilities ○ option to precompile the classes - avoid surprise in production

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Rails production mode ● Enabled by default in web.xml

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Deploy and Enjoy!

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Credits and sources ● Tomcat-logo by The Apache Tomcat Project Team ● Mug by Alex Getty from the Noun Project ● Diamond by MarkieAnn Packer from the Noun Project ● Box by Cornelius Danger from the Noun Project ● Clapperboard by Edgar Vargas from the Noun Project ● Questions by Rediffusion from the Noun Project ● Rails by Luis Martins from the Noun Project