Charles Nutter, one of the primary contributors to JRuby, reports promising progress in running Rails in JRuby. This could allow applications that blend J2EE and Rails functionality in interesting ways.

Another approach for deploying Rails in a Java/J2EE container is via the FastCGI interface. This forgoes some of the potential advantages of sharing a VM between Rails and Java, but it’s something you can do already, at least in Resin.

In the Rails discussion list, a user reports performance very close to Lighttpd using the Resin FastCGI servlet.

Unfortunately, the Caucho FastCGI servlet is closed source, and (I believe) Resin specific.

Does anyone have recommendations for an open source FCGI servlet for Tomcat and other servers?