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 ENV 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.