Forum: JRuby Accessing java classes in Jruby on Rails

Hai friends,

    I am a newbie in JRuby on Rails.I have so many java classes which i
need to integrate with my Jruby on Rails project.
Can you please tell me what are the steps for doing the same.....

Thanks,
Veena

Hi,

Take a look here: 
http://kenai.com/projects/jruby/pages/CallingJavaFromJRuby

Thanks,
  --Vladimir

On Tue, Mar 9, 2010 at 12:44 PM, Veena Jose <lists@ruby-forum.com> 
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Hai Vladimir,

Thanks for the link.....It was certainly informative......
But can you give me one example where a simple java class function is 
being accessed by a controller of Jruby on rails and display the result 
through its view...

From internet i am not getting a clear cut idea as what to do.....

If anyone can help please help me.....

Thanks,
Veena

class FooController < ApplicationController

  def index
    render :text=>org.foo.MyClass.new.myFunction()
  end

end

On Thu, Mar 18, 2010 at 7:19 AM, Veena Jose <lists@ruby-forum.com> 
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Yeah, it's really this easy.

1. require 'java' in that file
2. java_import classes (or reference them directly like Justin has below
3. use the classes

On Thu, Mar 18, 2010 at 8:46 AM, Justin Coyne <digger250@gmail.com> 
wrote:
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>> Veena
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Thank you Justin and Charles......But even now i am facing problem....

I want a jar file which contains only a simple java file (say 
'Factorial.java')to be accessible in Jruby.

foo_controller.rb
  require 'java'
  require '\test\test.jar'
class FooController < ApplicationController

  def index
    render :text=>Factorial.new.fact(5)
  end
end

"test" folder which contains the jar file is in "lib" folder

when i run the program it is showing error
"uninitialized constant FooController::Factorial"

Am i doing in a right way?please do correct me.....

Thanks,
Veena

Hi,

So, you're trying to use Factorial class from default package?
If yes, then you need to use: Java::Factorial

If no, then you need to use fully-qualified class name:
org.foo.Factorial or to java_import org.foo.Factorial
after require 'java'.

Thanks,
  --Vladimir

On Fri, Mar 19, 2010 at 6:53 AM, Veena Jose <lists@ruby-forum.com> 
wrote:
>  def index
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> If no, then you need to use fully-qualified class name:
> org.foo.Factorial or to java_import org.foo.Factorial

Hai Vladimir ,
 i am sorry.....what is this fully-qualified class name?
I am trying to include a java class(user defined) which is in a jar file 
into jruby on rails.....

1.I created Factorial.java file which contains fact() fn.
2.I jarred the file into test.jar
Now i want to use the fact() fn in my FooController/index.
Where i should put this jar file?

I am sorry if i am troubling you people a lot.I certainly need your 
help...

Thanks,
Veena

Java source files must be compiled into a .class file and then you can
put that .class file into the jar. You may want to walk through a
basic Java tutorial.

- Charlie (mobile)

On Mar 19, 2010, at 6:18 AM, Veena Jose <lists@ruby-forum.com> wrote:

> 1.I created Factorial.java file which contains fact() fn.
> Posted via http://www.ruby-forum.com/.
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Assuming

1. Java code compiled into class file
2. Jar file made from class file
3. Jar file required (require "lib/java/xxx/yyy.jar")

What are some possible reasons for getting:

@test = org.xxx.yyy.Zzzz.new("a").helloWorld()

NameError: cannot load Java class org.xxx.yyy.Zzzz
        from 
/home/max/.rvm/rubies/jruby-1.4.0/lib/ruby/1.8/irb/ruby-token.rb:102:in 
`get_proxy_or_package_under_package'
        from 
/home/max/.rvm/rubies/jruby-1.4.0/lib/ruby/site_ruby/shared/builtin/javasupport/java.rb:51:in 
`method_missing'
        from (irb):7:in `irb_binding'

Thanks,
Max

I do this a couple of ways

module MyClass
  include_package "factory"
end

then in your controller

 def index
   MyClass::Factory.new
 end

 -- or --

you can alias it in your controller like

 def Factory
    Java::Factory
 end

 Then you can use Factory.new as if it were a native class

AD


On Fri, Mar 19, 2010 at 5:10 PM, Max De marzi <lists@ruby-forum.com> 
wrote:
> NameError: cannot load Java class org.xxx.yyy.Zzzz
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On Fri, Mar 19, 2010 at 4:10 PM, Max De marzi <lists@ruby-forum.com> 
wrote:
> NameError: cannot load Java class org.xxx.yyy.Zzzz
Java does require that the directory structure in the jar file match
the package structure. So within the jar, you'd need
org/xxx/yyy/Zzzz.class to be an entry.

Them's the rules! :) If you do that, it should work fine.

- Charlie

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Mother pus bucket!

I've been bashing my head against the monitor all because I had a /src 
in my directory structure...