ENV Isolation

You can isolate your Ruby application's environment by clearing out the ENV variable by setting the jruby.runtime.env context parameter to false sample web.xml deployment descriptor :

<web-app>

  <context-param>
    <param-name>jruby.runtime.env</param-name>
    <param-value>false</param-value>
  </context-param>
  <context-param>
    <param-name>jruby.min.runtimes</param-name>
    <param-value>1</param-value>
  </context-param>

  <context-param>
    <param-name>jruby.max.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.rails.RailsServletContextListener</listener-class>
  </listener>

</web-app>

It accepts comma new line separated values as well, to allow for fine grained customizations :

  <context-param>
    <param-name>jruby.runtime.env</param-name>
    <param-value>
      DATABASE_URL=mysql://192.168.1.11/mydb
      PATH=/usr/local/bin,HOME=/home/tomcat,NAMES=Jozko, Ferko,Janko,GEM_HOME=&quot;&quot;
    </param-value>
  </context-param>

will end up setting DATABASE_URL, PATH, HOME, NAMES and GEM_HOME keys within Ruby runtimes ENV hash.

Warbler

Context parameters such as jruby.runtime.env are easy to set in using config/warble.rb :

Warbler::Config.new do |config|
  # Features: additional options controlling how the jar is built.
  # Currently the following features are supported:
  # - gemjar: package the gem repository in a jar file in WEB-INF/lib
  # - executable: embed a web server and make the war executable
  # - compiled: compile .rb files to .class files
  # config.features = %w(gemjar)

  # Additional files/directories to include, above those in config.dirs
  config.includes = FileList["db"]

  # Additional files/directories to exclude
  # config.excludes = FileList["lib/tasks/*"]

  # ...

  config.webxml.jruby.compat.version = "2.0"

  config.webxml.jruby.runtime.env = "DATABASE_URL=mysql://192.168.1.11/mydb\n" <<
    'PATH=/usr/local/bin,HOME=/home/tomcat,NAMES=Jozko, Ferko,Janko,GEM_HOME=""'

  # Control the pool of Rails runtimes. Leaving unspecified means
  # the pool will grow as needed to service requests. It is recommended
  # that you fix these values when running a production server!
  # If you're using threadsafe! mode, you probably don't want to set these values,
  # since 1 runtime(default for threadsafe mode) will be enough.
  # config.webxml.jruby.min.runtimes = 2
  # config.webxml.jruby.max.runtimes = 4
end