Slides for my Introduction to JRuby talk.

1. Introduction to
JRuby
Frederic Jean
fred@fredjean.net
1

2. First Encounter
2

3. Hello JRuby
3

4. Configuration
DSLs
Glue, Wiring
Dynamic Layer
Application Code
Stable Layer
Java, Statically typed
Legacy libraries
http://olabini.com/blog/2008/01/language-explorations/
4

5. Develop, Deploy, Build, Test, Monitor
Configuration
DSLs
Glue, Wiring
External System Integration
Dynamic Layer
Application Code
Stable Layer
Java, Statically typed
Legacy libraries
5

6. Ruby
6

7. Ruby is...
• Dynamically Typed
• Strongly Typed
• Everything is An Object
7

8. Dynamic Typing
• Variables Are Not Typed
• Type Evaluated at Run Time
• Duck Typing
8

9. (Almost) Everything is
an Object
9

10. Ruby Literals
# Strings
quot;This is a Stringquot;
'This is also a String'
%{So is this}
# Numbers
1, 0xa2, 0644, 3.14, 2.2e10
# Arrays and Hashes
['John', 'Henry', 'Mark']
{ :hello => quot;bonjourquot;, :bye => quot;au revoirquot;}
# Regular Expressions
quot;Mary had a little lambquot; =~ /little/
quot;The London Bridgequot; =~ %r{london}i
# Ranges
(1..100) # inclusive
(1...100) # exclusive
10

11. Symbols
:symbol
• String-like construct
• Only one copy in memory
11

12. Ruby Type
quot;helloquot;.class # => String
1.class # => Fixnum
10.3.class # => Float
[].class # => Array
{}.class # => Hash
Kernel.class # => Module
Object.class # => Class
:symbol.class # => Symbol
12

13. kind_of? vs respond_to?
puts 10.instance_of? Fixnum
puts 10.respond_to? :odd?
puts 10.respond_to? :between?
http://localhost:4567/code/instance_of.rb
13

14. Blocks
['John', 'Henry', 'Mark'].each { |name| puts quot;#{name}quot;}
File.open(quot;/tmp/password.txtquot;) do |input|
text = input.read
end
14

15. Ruby Classes
class Person
attr_accessor :name, :title
end
p = Person.new
15

16. Open Classes
class Fixnum
def odd?
self % 2 == 1
end
def even?
self % 2 == 0
end
end
http://localhost:4567/code/fixnum.rb
16

17. Namespacing
module Net
module FredJean
class MyClass
end
end
end
Net::FredJean::MyClass
17

18. Mixins
module Parity
def even?
self % 2 == 0
end
def odd?
self % 2 == 1
end
end
http://localhost:4567/code/parity.rb
18

19. Mixins
class Person
include Enumerable
attr_accessor :first_name, :last_name
def initialize(first_name, last_name)
@first_name = first_name
@last_name = last_name
end
def <=>(other)
self.last_name <=> other.last_name && self.first_name <=> other.last_name
end
def to_s
quot;#{first_name} #{last_name}quot;
end
end
http://localhost:4567/code/sorting.rb
19

20. Mixin Reflection
puts String.include? Enumerable
puts String.instance_of? Enumerable
puts String.kind_of? Enumerable
http://localhost:4567/code/include.rb
20

21. Executable Class Definition
class Message
if RUBY_PLATFORM =~ /java/i
def hello
puts quot;Hello From JRubyquot;
end
end
end
http://localhost:4567/code/env.rb
21

22. JRuby
22

23. JRuby
• Ruby Implementation on the JVM
• Compatible with Ruby 1.8.6
• Native Multithreading
• Full Access to Java Libraries
23

24. JRuby Hello World
java.lang.System.out.println quot;Hello JRuby!quot;
http://localhost:4567/code/jruby_hello.rb
24

25. Java Integration
require 'java'
25

26. JI: Ruby-like Methods
Java Ruby
Locale.US Locale::US
System.currentTimeMillis() System.current_time_millis
locale.getLanguage() locale.language
date.getTime() date.time
date.setTime(10) date.time = 10
file.isDirectory() file.directory?
26

27. JI: Java Extensions
h = java.util.HashMap.new
h[quot;keyquot;] = quot;valuequot;
h[quot;keyquot;]
# => quot;valuequot;
h.get(quot;keyquot;)
# => quot;valuequot;
h.each {|k,v| puts k + ' => ' + v}
# key => value
h.to_a
# => [[quot;keyquot;, quot;valuequot;]]
http://localhost:4567/code/ji/extensions.rb
27

28. JI: Java Extensions
module java::util::Map
include Enumerable
def each(&block)
entrySet.each { |pair| block.call([pair.key, pair.value]) }
end
def [](key)
get(key)
end
def []=(key,val)
put(key,val)
val
end
end
28

29. JI: Open Java Classes
class Java::JavaLang::Integer
def even?
int_value % 2 == 0
end
def odd?
int_value % 2 == 1
end
end
http://localhost:4567/code/ji/integer.rb
29

30. JI: Interface Conversion
package java.util.concurrent;
public class Executors {
// ...
public static Callable callable(Runnable r) {
// ...
}
}
30

31. JI: Interface Conversion
class SimpleRubyObject
def run
puts quot;hiquot;
end
end
callable = Executors.callable(SimpleRubyObject.new)
callable.call
http://localhost:4567/code/ji/if_conversion.rb
31

32. JI: Closure Conversion
callable = Executors.callable { puts quot;hiquot; }
callable.call
http://localhost:4567/code/ji/closure_conversion.rb
32

33. Develop, Deploy, Build, Test, Monitor
Configuration
DSLs
Glue, Wiring
External System Integration
Dynamic Layer
Application Code
Stable Layer
Java, Statically typed
Legacy libraries
33

34. Usage
• Runtime
• Wrapper around Java Code
• Calling From Java
• Utilities
34

35. JRuby as a Runtime
35

36. JRuby on Rails
• Ruby on Rails 2.1 and above is supported
• Direct support in Glassfish v3 Prelude
• http://kenai.com
• http://mediacast.sun.com
36

37. Warbler
jruby -S gem install warbler
jruby -S warble config
# => config/warble.rb
jruby -S warble
# => myapp.war
37

38. webmate
require 'rubygems'
require 'sinatra'
get '/*' do
file, line = request.path_info.split(/:/)
local_file = File.join(Dir.pwd, file)
if (File.exists?(local_file))
redirect quot;txmt://open/?url=file://#{local_file}&line=#{line}quot;
else
not_found
end
end
http://localhost:4567/code/webmate.rb
38

39. Wrapping Java Code
39

40. Swing Applications
frame = JFrame.new(quot;Hello Swingquot;)
• Reduce verbosity
• Simplify event handlers
http://localhost:4567/code/swing.rb
40

41. RSpec Testing Java
describe quot;An emptyquot;, HashMap do
before :each do
@hash_map = HashMap.new
end
it quot;should be able to add an entry to itquot; do
@hash_map.put quot;fooquot;, quot;barquot;
@hash_map.get(quot;fooquot;).should == quot;barquot;
end
end
JTestr Provides Ant and Maven integration
http://jtestr.codehaus.org
http://localhost:4567/code/hashmap_spec.rb
41

42. Java Calling JRuby
42

43. JSR-223
• Ships with Java 6
• Supports JRuby 1.1
https://scripting.dev.java.net/
43

44. JRuby Runtime
• Support the current release
• Specific to JRuby
• Subject to change
44

45. Spring Scripting
<lang:jruby id=quot;limequot; script-interfaces=quot;springruby.Limequot;
script-source=quot;classpath:lime.rbquot;/>
45

46. Utilities
46

47. Develop, Deploy, Build, Test, Monitor
Configuration
DSLs
Glue, Wiring
External System Integration
Dynamic Layer
Application Code
Stable Layer
Java, Statically typed
Legacy libraries
47

48. Build Utilities
• Rake
• Raven
• Buildr
48

49. Conclusion
49

50. Resources
• http://jruby.org
• http://wiki.jruby.org
• http://jruby.kenai.com
• http://jtester.codehaus.org
• http://raven.rubyforge.org
• http://buildr.apache.org
50