[proposal] make the jruby gem extension more java like

[mkristian]

make the jruby gem extension more java like. I just want to follow the way dropwizard "adds" their services to a jar file https://github.com/dropwizard/dropwizard/blob/master/dropwizard-metrics/src/main/resources/META-INF/services/io.dropwizard.metrics.ReporterFactory

• a jar with jruby extension has a file META-INF/services/org.jruby.Extension
• the file contains a list of class files which shall be loaded. assuming the loading of the class does activate the JRuby extension

example lib/ruby/shared/json/ext/parser.jar has the file META-INF/services/org.jruby.Extension with content

json.ext.ParserService

adding a jar to the jruby-classloader (via require or via $CLASSPATH << 'my.jar' will just do something along those lines to load the actual extension

for ( url : runtime.getJRubyClassLoader().getResources( "META-INF/services/org.jruby.Extension" ) ) {
  for (line : loadUrl( url ) {
     runtime.getJRubyClassLoader().loadClass( line );
  }
}

whether to keep a list of already loaded extension may or may not be needed.

[kares]

would have been a great feature (with some official docs) - loading by hand might not be for every-one.