jruby-mains

vision

• install your gem and jar dependencies into some directory /tmp/myapp
• pack the gems + jars into gems.jar
• pack the whole application as it into application.jar
• run the application from these jars or put them along jruby.jar and jruby-rack.jar into WEB-INF/lib

current situation

NOTE: at the time of writing you need to use jruby-complete.jar from https://oss.sonatype.org/content/repositories/snapshots/org/jruby/jruby-complete/1.7.20-SNAPSHOT/ for the examples. jruby-mains itself work with old jruby versions.

first pack all the gem and jar dependencies into one jar:

export JARS_HOME=/tmp/app/jars
export GEM_HOME=/tmp/app
export GEM_PATH=/tmp/app
gem install bundler
bundle install

rmdir /tmp/app/doc /tmp/app/extensions /tmp/app/build_info
rm -rf /tmp/app/cache
jar -cvf gems.jar -C /tmp/app .

now pack the application:

jar -cvf application.jar .

now run these jars with

java -cp application.jar:gems.jar:jruby-complete.jar org.jruby.Main -C uri:classloader:/ -S rackup

this is equivalent to (here the classloader finds the application on the classpath ".")

java -cp .:gems.jar:jruby-complete.jar org.jruby.Main -C uri:classloader:/ -S rackup

or very close to (the current directory is on the file system and not inside the classloader)

java -cp .:gems.jar:jruby-complete.jar org.jruby.Main -C . -S rackup

the last can be reduced to (since GEM_PATH and JARS_HOME needs to be set)

java -jar jruby-complete.jar $GEM_PATH/bin/rackup

the only difference is from where the application is loaded and where the current directory (-C) is pointing to.

note: if GEM_PATH and JARS_HOME are not set then JRuby is looking for gems and jars in uri:classloader:/.

ideally bundler should be only development dependency and then can be excluded.

what about war files ?

just put the jruby-complete.jar, jruby-rack.jar, application.jar and the gems.jar into WEB-INF/lib and configure your WEB-INF/web.xml to use the classpath-layout

<web-app>
  <context-param>
    <param-name>jruby.rack.layout_class</param-name>
    <param-value>JRuby::Rack::ClassPathLayout</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>

then the web-application uses the same loading semantic as the standalone execution.

of course you can just unpack the gems.jar and application.jar into WEB-INF/classes which does not make a difference since from both location all the ruby sources are loaded via the jruby-classloader.

using jruby-mains

this jruby-mains artifact expect the gems and jar dependencies be vendored at the root of the application.jar

JARS_HOME=. GEMS_HOME=. GEMS_PATH=. bundle install
jar -cvf application.jar .

and run it with

java -cp application.jar:jruby-complete.jar:jruby-mains.jar org.jruby.Main bin/rackup

packing the bin/* files into META-INF/jruby.home/bin will allow to execute them via the -S

java -cp application.jar:jruby-complete.jar:jruby-mains.jar de.saumya.mojo.mains.JarMain -S rackup

finally you can merge those three jar files into one and set the entry-point to de.saumya.mojo.mains.JarMain. this reduces the execution to

java -jar application-uber.jar -S rackup

some executables spawn a new ruby process which is not working from a jruby-complete exectution. but in such cases you can use the entry-point de.saumya.mojo.mains.ExtractingMain which unpacks the jar into a temporary directory and then executes the application.

to be continued