Newbie questions

[Kevin_SSLim]

Hi,
Here are some of my questions regarding java integration with ruby app.
Thanks in advance,
Kevin

1. Jruby on Rails
   I’m trying to have a java process created when rails app is started by
   ‘jruby -S start/server’.

I do this by putting my_init.rb under config/initializers

run on initialization

include Java
require “./lib/myjava.jar”
java_service = ServiceInitializer.new

where myjava.jar contains ServiceIntializer java class.

[Q1] Is this right way to initialize java process for rails app?
What is the general approach?
[Problem] Even when I do other operations, for example, ‘jruby -S
rake db:migrate’, this initialization routine seems to run.

2. Implementing java interface with jruby
   In my ServiceInitializer java code, I create an instance of ruby class
   as the implementation of one java interface.
   (I’ve used RubyFactory approach seen at
   久草av
   )
   I wanted this ruby implementation to be able to access all rails
   facilities that rails app uses.

[Q2] However, I had to manually connect to db and all, to get this
work. Does this sound right?
To me, it looks defeating its purpose of initializing from rails init.
My implementation class file rubyinterfacehandler.rb had to have all
these

require “rubygems”
require “active_record”
require “app/models/dbmodel.rb”

We had to do this manually since interface is

called from outside of rails?

ActiveRecord::Base::establish_connection(
:adapter=>“jdbcmysql”,
:database=>“db_development”,
:pool=>5,
:username=>“root”,
:password=>“”,
:host=>“localhost”)

class RubyInterfaceHandler
def interface_method
…
end
end

3. Creating war with warble and putting rails on Tomcat.
   [Problem] My RubyFactory who is instantiating rubyinterfacehandler
   cannot find rubyinterfacehandler.rb file which is located in rails
   project directory.
   I see the file gets populated in WEB-INF folder when war expanded.
   I tried to copy the ruby files to WEB-INF/lib also inside WEB-INF/lib/
   myjava.jar where RubyFactory class is but all didn’t work.
   [Q3] Where will be the root path from the java class that were in a
   jar file in the lib directory? How can I make it to find ruby files
   in rails app?
   [Q4] Shall I move out the java process initialization code to Tomcat
   web app context initialization area? Perhaps add a ContextListener?
   What is the general approach if I want to add webapp context init
   codes and still want to use warbler?

4. Running rails app using glassfish gem.
   [Problem] When I issue command ‘glassfish’, log shows followings where
   XXXX is the java interface class (implemented with ruby) that is in
   rails’ lib/myjava.jar.
   This must be coming out from RubyFactory

SEVERE: org.jruby.exceptions.RaiseException: cannot load Java class XXXX
Oct 28, 2009 1:55:13 PM com.sun.grizzly.config.GrizzlyServiceListener
SEVERE: java.lang.NoClassDefFoundError: XXXX
from java/lang/ClassLoader.java:700:in defineClass' from org/jruby/util/JRubyClassLoader.java:22:in defineClass’
from org/jruby/java/MiniJava.java:576:in
defineOldStyleImplClass' from org/jruby/java/MiniJava.java:194:in createOldStyleImplClass’
from org/jruby/javasupport/Java.java:1570:in
new_proxy_instance2' from org/jruby/java/proxies/JavaInterfaceTemplate.java:262:in jcreateProxy’
from org/jruby/java/proxies/JavaInterfaceTemplate.java:22:in
access$000' from org/jruby/java/proxies/JavaInterfaceTemplate.java:165:in call’
… 132 levels…
from /usr/local/jruby/lib/ruby/gems/1.8/gems/rails-2.3.4/lib/
initializer.rb:113:in `run’

[Q5] With glassfish, is there different way to specify classpath of
rails app libs? (for GrizzlyServiceListener?)
[Q6] Again, shall I move app context init code to somewhere else in
case with glassfish? Is there better approach?

[Kevin_SSLim]

On Mon, Nov 2, 2009 at 2:47 PM, Kevin S. Lim [email protected] wrote:

include Java
require “./lib/myjava.jar”
java_service = ServiceInitializer.new
where myjava.jar contains ServiceIntializer java class.
[Q1] Is this right way to initialize java process for rails app? What is
the general approach?

Seems like a reasonable thing to do.

[Problem] Even when I do other operations, for example, ‘jruby -S rake
db:migrate’, this initialization routine seems to run.

Right. The Rails environment gets loaded for many things, not just
when the server is run. You might be able to workaround by adding a
“lib/tasks/constants.rake” file with the contents “IN_RAKE = true”.
Then you can guard the above initialization code with “unless
defined?(IN_RAKE) … end”.

My implementation class file rubyinterfacehandler.rb had to have all these
:password=>“”,
:host=>“localhost”)
class RubyInterfaceHandler
def interface_method
…
end
end

You can use the ActiveRecord connection from initializers and pass
that into your Java class. The actual JDBC Connection object can be
reached with “ActiveRecord::Base.connection.raw_connection.connection”.
Yeah, it’s a bit much, but it should work.

You can also grab database connection info by grabbing the hash from
“ActiveRecord::Base.configurations[RAILS_ENV]”.

3. Creating war with warble and putting rails on Tomcat.
   [Problem] My RubyFactory who is instantiating rubyinterfacehandler cannot
   find rubyinterfacehandler.rb file which is located in rails project
   directory.
   I see the file gets populated in WEB-INF folder when war expanded.
   I tried to copy the ruby files to WEB-INF/lib also inside
   WEB-INF/lib/myjava.jar where RubyFactory class is but all didn’t work.
   [Q3] Where will be the root path from the java class that were in a jar file
   in the lib directory? How can I make it to find ruby files in rails app?

You shouldn’t assume any specific current directory. Rather, make use
of the load path to ensure that ruby and jar files are found. For
example, if you put your rubyinterfacehandler.rb and myjava.jar files
both in the ./lib directory of your Rails application, they should end
up in WEB-INF/lib of your war file. Since WEB-INF/lib should be put on
the load path by the Rails initialization process, simply requiring
them as follows should suffice:

require ‘rubyinterfacehandler’
require ‘myjava.jar’

[Q4] Shall I move out the java process initialization code to Tomcat web app
context initialization area? Perhaps add a ContextListener?
What is the general approach if I want to add webapp context init codes and
still want to use warbler?

You can still use Warbler to bundle java classes – see the Warbler
documentation and/or config/warble.rb for more options. Also, you can
copy Warbler’s web.xml.erb to your Rails config/ directory and
customize it to add more web.xml options.

    from org/jruby/java/MiniJava.java:576:in `defineOldStyleImplClass'

`run’
[Q5] With glassfish, is there different way to specify classpath of rails
app libs? (for GrizzlyServiceListener?)
[Q6] Again, shall I move app context init code to somewhere else in case
with glassfish? Is there better approach?

Try the approach above leveraging load path and see if that helps with
Glassfish too.

Cheers,
/Nick

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