jruby_rails.md

Ruby on Rails is a great application framework with a lot of advantages that are well documented elsewhere Occasionally, however, you may find yourself looking for a few tools just outside of the Rails toolbox. In some of those cases, JRuby can provide some additional options without giving up the expressiveness of Ruby or the fast prototyping and sane conventions of Rails.

Reasons to use JRuby

• Real Concurrency
• Java Interoperability
• Large gains in speed (once the JVM has warmed up)
• Excellent tooling around the JVM

These are all great reasons, especially concurrency and gains in speed. With a bit of discipline and a little trail and error, the average Rails developer can realize these benefits without giving up everything the ecosystem affords. Real threads used with application servers like Puma can allow more simultaneous connections to a single server instance, which can save money and resources over time. For the purposes of this multi-part tutorial we will be using Puma, but there are a number of great options (note: some options listed on the JRuby page are deprecated, dead, or otherwise ill-suited to Rails development).

The following assumes you are using OSX, but Ubuntu et.al. should also work basically the same way.

Let's get started from the very beginning:

1. install RVM

\curl -sSL https://get.rvm.io | bash

2. Check for Rubies

rvm list known

Find the JRuby section and highlight jruby-9.0.0.0.pre1

3. Install JRuby

rvm install jruby-9.0.0.0.pre1

This will likely take a few minutes, so go make a cup of coffee or tea.

4. Once that is done run:

rvm list

This will show you all of your installed rubies. If jruby-9.0.0.0.pre1 isn't on the list then try step 3 again, possibly running rvm uninstall jruby-9.0.0.0.pre1 first. If jruby-9.0.0.0.pre1 isn't proceeded by either => or =* then run rvm default use jruby-9.0.0.0.pre1 to set JRuby 9k as your current and default Ruby.

5. Next, install Rails for JRuby

gem install rails -v '4.1.9' --platform jruby

As of the writing of this post, the activerecord-jdbc-adapter for Postgres does not work with Active Record >= 4.2, so we'll have to make due with ```Rails 4.1.9`` until this issue gets addressed. When this changes I'll update the post.

6. Start a new Rails project with JRuby

rails _4.1.9_ new jruby_rails_tutorial --database=postgresql

If you are still using JRuby as your current ruby, then all of the correct JRuby boilerplate should be setup here. If you see Using activerecord-jdbcpostgresql-adapter x.x.x in the console, then you're on the right track.

Some notes about this command:

• _4.1.9_ specifies the version of Rails in case you have multiple versions installed.
• --database=postgresql sets the database as Postgres
• There is no need to run Jruby -S before rails new since you're using RVM.

7. Next cd into you app directory and spin up the server

   run the server as follows:

rails server

This will take a few seconds as the JVM starts up and WEBrick boots.

8. Visit the app at http://localhost:3000

   click "About your application’s environment"

   It should look something like:

   

   Good Job, you're doing JRuby on Rails

You can find the code so far on GitHub.

##Part 2 is Coming Soon.