JRuby and You

JRuby and You
Hiro Asari
Engine Yard

Wednesday, October 26, 11

History
September 10, 2001

Source: Wikipedia


Project Status

• Current stable release: 1.6.5 (Oct 25, 2011)
• Rails 3.1-compatible


What’s next in 1.7?

• JSR 292 (a.k.a. invokedynamic) support
• Improved Ruby 1.9 support


What’s in it for Java
programmers?

• REPL
• Testing frameworks
• Fun


What’s in it for
Rubyists?
• Real threads
• No more GIL
• Mature garbage collector
• Easy deployment


Try JRuby
http://jruby.org/tryjruby


Getting JRuby

wget http://bit.ly/jruby_bin_165 |
tar xzvf -

export PATH=$PATH:$PWD/jruby-1.6.5/bin


jruby -S irb

Java Integration

require 'java'


Loading JAR

require 'example.jar'


Importing Java Class

StringBuffer = java.lang.StringBuffer
sb = StringBuffer.new "foo"


java_import

java_import java.lang.StringBuffer
java_import 'java.lang.StringBuffer'


Static methods

java.lang.System.currentTimeMillis
java.lang.System.current_time_millis


Static Fields

java_import java.util.logging.Logger
java_import java.util.loggin.Level

Logger.global.log Level::SEVERE, "…"


Constructor

URL.new 'http://engineyard.com'
URL.new 'http', 'engineyard.com', '/'


Instance methods
#given
# void setPrice(int):
car.setPrice(2000)
car.price = 2000

# int getPrice()
car.price


Explicit Coercion

measurement = 5
measurement.to_java


Overloaded methods
public class C {
public static String method(String s) {
return "String";
}
public static String method(long l) {
return "long";
}
}


Overloaded methods

obj = C.new
obj.method("foo") # => "String"
obj.method(5) # => "long"


Overloaded methods
public class C {
public String method(int i) {
return "int";
}
public String method(long l) {
return "long";
}
}


Overloaded methods

obj = C.new
obj.method(5) # => "long"
obj.method(5.to_java(Java::int))
obj.java_send :method, [Java::int], 5


Java Interfaces

callable =
java.util.concurrent.Executors.callable do
puts "foo"
end

callable.call


Complex Example with
Akka
Java source: http://bit.ly/lTClmr
Ruby source: https://gist.github.com/1013227
http://www.engineyard.com/blog/2011/using-
java-from-ruby-with-jruby-irb/


GUI

Redcar

http://redcareditor.com/


Grafting Rails into
Spring MVC


Pet Clinic

• Example
database-
backed web
app for
Spring
framework


Requests

JRuby

/ /vets /rack/ Java/
Spring

App

Adding Route
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>


Cucumber

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


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"


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


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>

+ 
+ <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>
+

<dependency>
<groupId>org.junit</groupId>

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).

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


Requests

/ /vets JRuby

/owners Java/
/ /vets /owners /1/pets Spring

App

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>

The Book

http://pragprog.com/book/
jruby/using-jruby

25% off for one week
only: http://bit.ly/vd4Mhj


Engine Yard

500 free hours
http://engineyard.com


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


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