Rails and Java EE integration - Servlet co-bundled and invoked from Rails

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One of the several advantages of deploying Rails applications on GlassFish is - co-hosting Rails and Java EE applications in the same container. The screencast #web9 shows how Rails applications can be easily deployed on GlassFish.

This blog takes the JRuby-on-Rails (jRoR) and Java EE integration to the next level. It show how a Java EE Servlet can be co-bundled within a jRoR application. And then it shows how such a servlet can be easily invoked from a Rails view. It uses WAR-based mode for deploying jRoR applications on GlassFish.

Here are the detailed steps:

In an existing JRuby 1.1 RC3 installation (enabled with Rails), install the required gems:

~/testbed/jruby-1.1RC3 >bin/jruby -S gem install activerecord-jdbc-adapter
JRuby limited openssl loaded. gem install jruby-openssl for full support.
http://wiki.jruby.org/wiki/JRuby_Builtin_OpenSSL
Successfully installed activerecord-jdbc-adapter-0.8
1 gem installed
Installing ri documentation for activerecord-jdbc-adapter-0.8...
Installing RDoc documentation for activerecord-jdbc-adapter-0.8...

Create a Rails app as:

~/testbed/jruby-1.1RC3/samples/rails >../../bin/jruby -S rails railsee1
      create
      create app/controllers
      create app/helpers
      create app/models
      create app/views/layouts
      create config/environments
      create config/initializers
      create db
      create doc
      create lib
      create lib/tasks
      create log
      create public/images
      create public/javascripts
      create public/stylesheets
      create script/performance
      create script/process
      create test/fixtures
      create test/functional
      create test/integration
      create test/mocks/development
      create test/mocks/test
      create test/unit
      create vendor
      create vendor/plugins
      create tmp/sessions
      create tmp/sockets
      create tmp/cache
      create tmp/pids
      create Rakefile
      create README
      create app/controllers/application.rb
      create app/helpers/application_helper.rb
      create test/test_helper.rb
      create config/database.yml
      create config/routes.rb
      create public/.htaccess
      create config/initializers/inflections.rb
      create config/initializers/mime_types.rb
      create config/boot.rb
      create config/environment.rb
      create config/environments/production.rb
      create config/environments/development.rb
      create config/environments/test.rb
      create script/about
      create script/console
      create script/destroy
      create script/generate
      create script/performance/benchmarker
      create script/performance/profiler
      create script/performance/request
      create script/process/reaper
      create script/process/spawner
      create script/process/inspector
      create script/runner
      create script/server
      create script/plugin
      create public/dispatch.rb
      create public/dispatch.cgi
      create public/dispatch.fcgi
      create public/404.html
      create public/422.html
      create public/500.html
      create public/index.html
      create public/favicon.ico
      create public/robots.txt
      create public/images/rails.png
      create public/javascripts/prototype.js
      create public/javascripts/effects.js
      create public/javascripts/dragdrop.js
      create public/javascripts/controls.js
      create public/javascripts/application.js
      create doc/README_FOR_APP
      create log/server.log
      create log/production.log
      create log/development.log
      create log/test.log

Install Goldspike plugin in the application as:

~/testbed/jruby-1.1RC3/samples/rails/railsee1 >../../../bin/jruby script/plugin install svn://rubyforge.org/var/svn/jruby-extras/trunk/rails-integration/plugins/goldspike
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/test
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/test/war_config_test_config.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/test/test_java_library.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/test/test_maven_library.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/test/test_create_war.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/Rakefile
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/init.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/tasks
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/tasks/war.rake
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib/util.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib/war_config.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib/run.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib/java_library.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib/packer.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/lib/create_war.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/install.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/generators
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/generators/goldspike
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/generators/goldspike/goldspike_generator.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/generators/goldspike/templates
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/generators/goldspike/templates/web.xml.erb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/generators/goldspike/templates/war.rb
A    /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1/vendor/plugins/goldspike/README
Exported revision 960.
      exists config
      create config/war.rb
      create WEB-INF
      create WEB-INF/web.xml.erb

Optionally Warbler may be used for packaging and Goldspike for dispatching.

Create a Java library with Servlet code

Using NetBeans IDE, create a project of type "Java Class Library" and specify the name "HelloServlet".
Right-click on the project, select "New" and "Servlet...". Enter the class name as "HelloServlet" and package as "server" as shown below:
Right-click on the project, select Properties and in "Libraries", "Compile Tab Libraries" add "javaee.jar" from GlassFish v2 UR1 "lib" directory.

Change the "try" block in "processRequest" method to following:

String name = request.getParameter("name");
if (name == null || name.equals(""))
name = "Duke";

out.println("<h1>Servlet HelloServlet at " + request.getContextPath () + " says Hello " + name + "!</h1>");

Right-click on the project and select "Clean and Build".

Configure Rails app for Servlet

In your Rails application directory, add the following fragments to "WEB-INF/web.xml.erb":

<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>server.HelloServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>

Create "WEB-INF/lib" directory and copy "HelloServlet.jar" from the "dist" directory of NetBeans project here.

Create a WAR file as:

~/testbed/jruby-1.1RC3/samples/rails/railsee1 >../../../bin/jruby -S rake war:standalone:create
(in /Users/arungupta/testbed/jruby-1.1RC3/samples/rails/railsee1)
info: Assembling web application
info: Packing needed Java libraries ...
info:   adding Java library jruby-complete-1.1RC3
info:   adding Java library goldspike-1.6
info:   adding Java library activation-1.1
info:   adding Java library commons-pool-1.3
info:   adding Java library bcprov-jdk14-124
info: Packing needed Ruby gems ...
info:   adding Ruby gem rails version 2.0.2
info:   adding Ruby gem rake version 0.8.1
info:   adding Ruby gem activesupport version 2.0.2
info:   adding Ruby gem activerecord version 2.0.2
info:   adding Ruby gem actionpack version 2.0.2
info:   adding Ruby gem actionmailer version 2.0.2
info:   adding Ruby gem activeresource version 2.0.2
info:   adding Ruby gem activerecord-jdbc-adapter version 0.8
info: Packing needed files ...
info: Creating web archive

Deploy the WAR to GlassFish v2 UR1 as:

~/testbed/glassfish/v2ur1/glassfish/bin >./asadmin deploy ~/testbed/jruby-1.1RC3/samples/rails/railsee1/railsee1.war
The bundled Servlet is now accessible at "http://localhost:8080/railsee1/hello". The default browser output looks like:

And passing a parameter to the URL as "http://localhost:8080/railsee1/hello?name=Arun" shows the output as:

With this, your Java EE Servlet is now bundled with your Rails application deployed on GlassFish v2 UR1.

Now, lets add Controller and View to Rails application and invoke this servlet from there to show complete integration with Rails.

Create a new Controller and View as

~/testbed/jruby-1.1RC3/samples/rails/railsee1 >../../../bin/jruby script/generate controller home index
JRuby limited openssl loaded. gem install jruby-openssl for full support.
http://wiki.jruby.org/wiki/JRuby_Builtin_OpenSSL
      exists app/controllers/
      exists app/helpers/
      create app/views/home
      exists test/functional/
      create app/controllers/home_controller.rb
      create test/functional/home_controller_test.rb
      create app/helpers/home_helper.rb
      create app/views/home/index.html.erb

Change the generated controller in "app/controllers/home_controller.rb" to:

class HomeController < ApplicationController

include Java

def index
        url = java.net.URL.new("http://localhost:8080/railsee1/hello");
        conn = url.open_connection;
        reader = java.io.BufferedReader.new(java.io.InputStreamReader.new(conn.get_input_stream));
        @servlet_output = "";
        input_line = reader.read_line;
        while input_line != nil
                @servlet_output << input_line;
                input_line = reader.read_line;
        end
        reader.close;
end
end

Change the generated view in "app/views/home/index.rhtml.erb" to:

<h1>Home#index</h1>
<p>Find me in app/views/home/index.html.erb</p>

<%= @servlet_output %>
Re-create the WAR as describd in bullet # 6 above. And now "http://localhost:8080/railsee1/home/index" shows the output as shown:

This shows how a Java EE 5 Servlet can be easily invoked from a Rails application deployed on GlassFish. JRuby-on-Rails and GlassFish allows you to leverage business knowledge that exists in Java EE applications very easily and still providing Rails agility.

Reference:

http://blogs.sun.com/arungupta/entry/rails_and_java_ee_integration

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Rails and Java EE integration - Servlet co-bundled and invoked from Rails