The document discusses using JRuby to integrate Ruby and Rails into an existing Java/Spring application. It describes using JRuby, Warbler, Rack, and Rails to refactor the application in stages from small changes like adding tests and routing, to medium changes like layering on Rails, to a large refactor of the directory structure and bootstrapping Rails within the Spring context.

1. Spring into Rails
Hiro Asari
Engine Yard, Inc.

2. Imagine…
Maintaining enterprise
web application written
in Java…

3. Imagine…

4. public class FooTest {
static Foo foo;
public FooTest() {
}
@BeforeClass
public static void setUpClass() throws Exception {
}
@AfterClass
public static void tearDownClass() throws Exception {
}
@Before
public void setUp() {
foo = new Foo();
}
@Test
public void testReturn42() {
assertEquals(…, …);
}
}

5. public class FooTest {
static Foo foo;
public FooTest() {
}
@BeforeClass
public static void setUpClass() throws Exception {
}
@AfterClass
public static void tearDownClass() throws Exception {
}
@Before
public void setUp() {
foo = new Foo();
}
@Test
public void testReturn42() {
assertEquals(42, foo.return42());
}
}

6. public class FooTest {
static Foo foo;
public FooTest() {
}
@BeforeClass
public static void setUpClass() throws Exception {
}
@AfterClass
public static void tearDownClass() throws Exception {
}
@Before
public void setUp() {
foo = new Foo();
}
@Test
public void testReturn42() {
assertEquals(42, foo.return42());
# or is it assertEquals(foo.return42(), 42) ?
}
}

7. What if…
You didn’t have to
write in Java?

8. JRuby
A Ruby language
implementation on JVM
10 years (+ 1 day) since
the first recorded commit
Supporting Rails since
May, 2006
Latest release is 1.6.4 (22
August, 2011)

9. JRuby Jam Session
15:00 BST 15 Setembro, 2011
http://pages.engineyard.com/JRubyInDepth.html

10. Warbler
From a Ruby/Rails/
Merb/Rack application,
create a WAR file for
use with Java
application container
such as Tomcat and
Glassfish
http://www.pbase.com/wwcsig/image/59657656

11. Application Servers
Trinidad (Tomcat-based)
TorqueBox (JBoss-based)
Kirk (Jetty-based)

12. $ jruby -S bundle install
Using backports (2.0.3)
Using builder (3.0.0)
⋮
Using cucumber (0.10.2)
Using cucumber-rails (0.4.0)
Using database_cleaner (0.6.6)
Using launchy (1.0.0) from https://github.com/copiousfreetime/launchy.git (at v1.0.0)
Using monkey-lib (0.5.4)
Using rspec-core (2.1.0)
Using rspec-expectations (2.1.0)
Using rspec-mocks (2.1.0)
Using rspec (2.1.0)
Using rspec-rails (2.1.0)
Using tilt (1.2.2)
Using sinatra (1.2.1)
Using sinatra-sugar (0.5.0)
Using sinatra-advanced-routes (0.5.1)
Using sinatra-reloader (0.5.0)
Using spoon (0.0.1)
Using bundler (1.0.17)
Your bundle is complete! It was installed into ./bundler

13. Rack
http://rack.rubyforge.org/
Specifications for how Ruby-based web
applications should behave
jruby-rack 1.0.10 (based on rack 1.3.2)

14. Pet Clinic
Example database-
backed web app for
Spring framework

15. Enterprise software
Long-running projects with legacy codebases
Easy maintenance is important
Testing is critical

16. Refactoring
Write test first

17. RSpec
http://relishapp.com/rspec
Behavior-driven development tool for Ruby

18. RSpec
# bowling_spec.rb
require 'bowling'
describe Bowling, "#score" do
it "returns 0 for all gutter game" do
bowling = Bowling.new
20.times { bowling.hit(0) }
bowling.score.should == 0
end
end

19. Cucumber
http://cukes.info
Testing framework for describing software
behavior in plain English

20. Cucumber
Feature: Pets
Scenario: Edit Pet
Given I am on the owners search page
And I press "Find Owners"
And I follow "George Franklin"
And I follow "Edit Pet"
When I fill in "Name" with "Leoni"
And press "Update Pet"
Then I should see "Leoni"

21. http://bit.ly/refactoring-to-rails

22. Small refactoring
Give Ruby a foot in the door

23. Requests
/ /vets Java/
Spring
App

24. Requests
JRuby
/ /vets /rack/ Java/
Spring
App

25. Cucumber test
diff --git a/src/main/webapp/WEB-INF/jsp/vets.jsp b/src/main/webapp/WEB-INF/jsp/vets.jsp
index cff2154..0d99817 100644
--- a/src/main/webapp/WEB-INF/jsp/vets.jsp
+++ b/src/main/webapp/WEB-INF/jsp/vets.jsp
@@ -23,7 +23,7 @@
<table class="table-buttons">
<tr>
<td>
- <a href="<spring:url value="/vets.xml" htmlEscape="true" />">View as XML</a>
+ <a href="<spring:url value="/rack/vets.xml" htmlEscape="true" />">View as XML</a>
</td>
</tr>
</table>

26. Cucumber test
Stand by while Tomcat finishes booting...
Using the default profile...
............................................................F-.............
(::) failed steps (::)
expected: /xml/,
got: "text/html;charset=utf-8" (using =~)
Diff:
@@ -1,2 +1,2 @@
-/xml/
+text/html;charset=utf-8
(RSpec::Expectations::ExpectationNotMetError)
org/jruby/RubyProc.java:268:in `call'
./features/step_definitions/xml_json_steps.rb:12:in `(root)':in `/^I should see
an XML document$/'
features/vets.feature:6:in `Then I should see an XML document'
Failing Scenarios:
cucumber features/vets.feature:3 # Scenario: View vets as XML
13 scenarios (1 failed, 12 passed)
75 steps (1 failed, 1 skipped, 73 passed)
0m7.709s
rake aborted!
Cucumber failed

27. diff --git a/pom.xml b/pom.xml
index 9e22f83..0810701 100644
--- a/pom.xml
+++ b/pom.xml
@@ -211,6 +211,18 @@
<scope>provided</scope>
</dependency>
+ <!-- JRuby and JRuby-Rack -->
+ <dependency>
+ <groupId>org.jruby</groupId>
+ <artifactId>jruby-complete</artifactId>
+ <version>1.6.0</version>
+ </dependency>
+ <dependency>
+ <groupId>org.jruby.rack</groupId>
+ <artifactId>jruby-rack</artifactId>
+ <version>1.0.8</version>
+ </dependency>
+
<!-- Test dependencies -->
<dependency>
<groupId>org.junit</groupId>

28. diff --git a/src/main/webapp/WEB-INF/web.xml b/src/main/webapp/WEB-INF/web.xml
index 8d02684..60ed6cb 100644
--- a/src/main/webapp/WEB-INF/web.xml
+++ b/src/main/webapp/WEB-INF/web.xml
@@ -87,6 +87,21 @@
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
+
+ <listener>
+ <listener-class>org.jruby.rack.RackServletContextListener</listener-class>
+ </listener>
+
+ <servlet>
+ <servlet-name>rack</servlet-name>
+ <servlet-class>org.jruby.rack.RackServlet</servlet-class>
+ </servlet>
+
+ <servlet-mapping>
+ <servlet-name>rack</servlet-name>
+ <url-pattern>/rack/*</url-pattern>
+ </servlet-mapping>
+
<!--
Defines the 'default' servlet (usually for service static resources).

29. diff --git a/src/main/webapp/WEB-INF/lib/app.rb b/src/main/webapp/WEB-INF/lib/
app.rb
index 6ab5b3c..4398fb4 100644
--- a/src/main/webapp/WEB-INF/lib/app.rb
+++ b/src/main/webapp/WEB-INF/lib/app.rb
@@ -1,6 +1,33 @@
require 'builder'
require 'erb'
+require 'spring_helpers'
+
+helpers do
+ include Spring
+end
get '/rack/' do
'<h1>Sinatra</h1>'
end
+
+get '/rack/vets.xml' do
+ content_type 'application/vnd.petclinic+xml'
+ builder do |xml|
+ xml.instruct!
+ xml.vets do
+ clinic.vets.each do |vet|
+ xml.vetList do
+ xml.id vet.id
+ xml.firstName vet.firstName
+ xml.lastName vet.lastName
+ vet.specialties.each do |spec|
+ xml.specialties do
+ xml.id spec.id
+ xml.name spec.name
+ end
+ end
+ end
+ end
+ end
+ end
+end

30. Medium refactoring
Layer on the Rails

31. Requests
JRuby
/ /vets /rack/ Java/
Spring
App

32. Requests
/owners Java/
/ /vets /owners /1/pets Spring
App

33. Requests
/ /vets JRuby
/owners Java/
/ /vets /owners /1/pets Spring
App

34. diff --git a/src/main/webapp/WEB-INF/web.xml b/src/main/webapp/WEB-INF/web.xml
index 60ed6cb..f64b34d 100644
--- a/src/main/webapp/WEB-INF/web.xml
+++ b/src/main/webapp/WEB-INF/web.xml
@@ -92,16 +92,6 @@
<listener-class>org.jruby.rack.RackServletContextListener</listener-class>
</listener>
- <servlet>
- <servlet-name>rack</servlet-name>
- <servlet-class>org.jruby.rack.RackServlet</servlet-class>
- </servlet>
-
- <servlet-mapping>
- <servlet-name>rack</servlet-name>
- <url-pattern>/rack/*</url-pattern>
- </servlet-mapping>
-
<!--
Defines the 'default' servlet (usually for service static resources).
@@ -162,6 +152,16 @@
<url-pattern>/</url-pattern>
</servlet-mapping>
+ <filter>
+ <filter-name>RackFilter</filter-name>
+ <filter-class>org.jruby.rack.RubyFirstRackFilter</filter-class>
+ </filter>
+
+ <filter-mapping>
+ <filter-name>RackFilter</filter-name>
+ <url-pattern>/*</url-pattern>
+ </filter-mapping>
+
<filter>
<filter-name>httpMethodFilter</filter-name>
<filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>

35. Large refactoring
Full-on Rails development

36. Large refactoring
Change directory structure; move files from
WEB-INF/* to Rails directory structure
In Rails initializer, create a Spring context to boot
the Spring app
Ensure classpath includes Spring jars.

37. Large refactoring
Configure warbler to ensure necessary files are
included in WAR file

38. TMTOWTDI
<html>
<head>
</head>
JSP <body>
###
</body>
Mixing JSP and </html>
JRuby output +
<div>
Sinatra <h1>App</h1>
</div>

39. Questions?
Twitter @hiro_asari
G+ http://gplus.to/hiroasari
LinkedIn http://linkedin.com/in/hiroasari
asari.ruby@gmail.com
hasari@engineyard.com
http://github.com/banzaiman
http://www.flickr.com/photos/42033648@N00/372887164

40. Obligado!
Twitter @hiro_asari
G+ http://gplus.to/hiroasari
LinkedIn http://linkedin.com/in/hiroasari
asari.ruby@gmail.com
hasari@engineyard.com
http://github.com/banzaiman
http://www.flickr.com/photos/42033648@N00/372887164