Rack Application with Ruby Maven

setup

the expected layout for such a project looks like this:

.
├── Gemfile
├── config.ru
├── lib
|   └── ....
└── public

next we need a Mavenfile which configures the WAR-plugin and GEM-plugin.

gemfile

packaging :war

pom( 'org.jruby:jruby', '1.7.13' )
jar( 'org.jruby.rack:jruby-rack', '1.1.14', 
     :exclusions => [ 'org.jruby:jruby-complete' ] )

jruby_plugin!( :gem,
               :includeLibDirectoryInResources => true,
			   :includeRubygemsInTestResources => false,
               :includeRubygemsInResources => true )
			   
plugin( :war, '2.2',
        :warSourceDirectory => '${basedir}/public',
        :webResources => [ { :directory => '${basedir}',
                             :targetPath => 'WEB-INF',
                             :includes => [ 'config.ru' ] } ] )

now we need the public/WEB-INF/web.xml

<web-app>
  <context-param>
    <param-name>jruby.max.runtimes</param-name>
    <param-value>1</param-value>
  </context-param>
  <context-param>
    <param-name>jruby.min.runtimes</param-name>
    <param-value>1</param-value>
  </context-param>
  <filter>
    <filter-name>RackFilter</filter-name>
    <filter-class>org.jruby.rack.RackFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>RackFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  <listener>
    <listener-class>org.jruby.rack.RackServletContextListener</listener-class>
  </listener>
</web-app>

for more config options see https://github.com/jruby/jruby-rack. now we need to get ruby-maven ;)

the layout changed to

.
├── Gemfile
├── Mavenfile
├── config.ru
├── lib
|   └── ....
└── public
    └── WEB-INF
        └── web.xml

almost ready to pack the war file, just make sure Ruby-Maven is installed:

gem install ruby-maven

maybe bundle the gems first - optional ;-)

bundle install

after running

rmvn package

we have (assume you are in 'my_application' directory)

.
....
└── pkg
    ├── my_application.war
    ├── classes
    └── rubygems
        ├── bin
        ├── build_info
        ├── cache
        ├── doc
        ├── gems
        └── specifications

one note about bundler: make sure that the application does NOT rely on the auto-require feature of bundler, you do not need the Gemfile inside the war. this example assumes that fact.

compatiblity with servlet containers

rubygems does not work with some classloader. in such a case you can setup the load-path in WEB-INF/init.rb like

$:.unshift "classpath:/gems/dm-transactions-1.2.0/lib"
$:.unshift "classpath:/gems/fastercsv-1.5.5/lib"
$:.unshift "classpath:/gems/ixtlan-error-handler-0.4.5/lib"
$:.unshift "classpath:/gems/dm-validations-1.2.0/lib"

this solves most of the gem related classloader problems !

other classloaders have a problem with those packed jars inside jruby-stdlib. unpacking that jruby-stdlib.jar into WEB-INF/classes does help. adding explicit dependencies of the default gems to your Gemfile could help. retrieve the list of default gems like this:

GEM_PATH= GEM_HOME= jruby -S gem list -l

example of how to unpack JRuby-Stdlib:

gemfile

packaging :war

jruby_version = '1.7.13'
pom( 'org.jruby:jruby', jruby_version
     :exclusions => ['org.jruby:jruby-stdlib' ])
# needed to install gems for the build itself
jar( 'org.jruby:jruby-stdlib', jruby_version,
      :scope => :provided )

jar( 'org.jruby.rack:jruby-rack', '1.1.14', 
     :exclusions => [ 'org.jruby:jruby-complete' ] )

jruby_plugin!( :gem,
               :includeLibDirectoryInResources => true,
			   :includeRubygemsInTestResources => false,
               :includeRubygemsInResources => true )
			   
plugin( :dependency, '2.8', :phase => 'prepare-package'
        :artifactItems => [ { :groupId => 'org.jruby',
                              :artifactId => 'jruby-stdlib',
                              :version => jruby_version,
                              :outputDirectory => '${project.build.outputDirectory}' } ] ) do
  execute_goal( :unpack )
end

plugin( :war, '2.2',
        :warSourceDirectory => '${basedir}/public',
        :webResources => [ { :directory => '${basedir}',
                             :targetPath => 'WEB-INF',
                             :includes => [ 'config.ru' ] } ] )

that is much more then the initial setup.

heroku

with heroku you install java applications. one advantage of this approach is that you can also take advantage of the jar dependencies from your Jarfile and add two more declarations for heroku. to use the Jarfile add

 jarfile :classpath => :java

which tells Ruby-Maven to add to the java-classpath and not to the jruby-classloader. to setup heroku add

 properties 'tesla.dump.pom' => 'pom.xml', 'tesla.dump.readOnly' => true

 plugin( :dependency, '2.3',
         :phase => :package ) do
   execute_goal( :copy,
                 :artifactItems => [ { :groupId => 'com.github.jsimone',
                                       :artifactId => 'webapp-runner',
                                       :version => '7.0.22',
                                       :destFileName => 'webapp-runner.jar' } ] )
 end

the properties just tells Ruby-Maven to dump a pom.xml. the second statement is the webrunner for heroku. with this you also can start your application locally with

 $ rmvn package
 $ java -jar target/dependency/webapp-runner.jar target/*.war

note the rmvn which will generate the pom.xml needed for heroku ! now you need a Procfile for heroku:

 web:    java $JAVA_OPTS -jar target/dependency/webapp-runner.jar --port $PORT target/*.war

IMPORTANT is to create the heroku application with picked buildpack

 heroku create --buildpack https://github.com/heroku/heroku-buildpack-java

now you can install you application on heroku the usual way. for more info see also https://github.com/heroku/java-sample#configure-maven-to-download-webapp-runner.

when you deploy to heroku maven will download the gems and the jars declared in Gemfile and Jarfile.

customize when you have a different application layout

use app instead of a lib directory add

 resource :directory => '.', :includes => [ 'app/**' ]

and the :includeLibDirectoryInResources => true is not needed anymore.

for rails you need to add further directories (untested from my side and might need some more attention)

 resource :directory => '.', :includes => [ 'app/**', 'config/**', 'lib/**' ]