Re: [xwiki-devs] adding a new jsr-223 scripting language to xwiki (clojure)

(I forgot to send this out a while back, probably because I didn't want to distract myself with thinking about integrating Xwiki and Clojure any more at the time :-) ) Got an interesting reply back from the Clojure list regarding JSR-223 support: http://groups.google.com/group/clojure/msg/ad811b69d448e3db (see below). Regarding this message, and Xwiki's JSR-223 API usage, a question: Does Xwiki's JSR-223 usage rely on the "Invocable interface" or the "Compilable-interface" ? Looking into what this all means, http://java.sun.com/developer/technicalArticles/J2SE/Desktop/scripting/ states Invokable is optional: Meanwhile., the author, Phil Frank, claims that Compilable is not implemented for his JSR-223 bridge, and may not be necessary for Clojure: Does Xwiki need anything from this Compilable interface, or will it's lack of implementation be a problem? As to the "active instance" issues brought up -- will these apply when running multiple active instances out of a web container like tomcat? According to http://tomcat.apache.org/tomcat-6.0-doc/class-loader-howto.html there's a separate classloader per web application, which means, I guess, that the JSR-223 clojure implementation will share any static initialization from the Clojure implementation: So if all Clojure under Xwiki is shared via a common "WebAppX" classloader under the Servlet Spec, does this mean that all Clojure instances would share a :"symbol table" and their values/properties? This could either become a useful feature, or an egregious security hole in a multi-wikli environment. ---------------- From: Phil Frank To: Clojure <clojure(a)googlegroups.com> On Aug 1, 2:36=A0am, Niels Mayer <nielsma...(a)gmail.com> wrote: I'm the author of the JSR 223 bridge for Clojure. At the moment, I have several uncommitted changes (mainly related to wrapping it up in a nice OSGi service component (to be used optionally). The Invocable- stuff is not implemented at the moment, but will be painless to implement. The Compilable-interface is a bit harder to do, and given Clojure's AOT compilation, I'm not sure if there's really a use case (because if you use require within a small script, Clojure will already out of the box transparently choose a compiled implementation, given a proper classpath setup). It's not quite the same, but comes pretty close. Aside from that, I have some unresolved design issues regarding isolation of engines; this works differently for Clojure than for other dynamic languages for the reasons explained below. Due to the static initialization of the Clojure runtime, it is much harder to create different independent Clojure-engine instances, since this would require loading each Clojure-runtime under a separate classloader, which I am not opposed to, but was unable to implement. At the moment, I'm using a weird kind of isolation in which each Clojure-engine runs in its own thread, using a shared runtime, and bindings are isolated by pushing and popping them. I'm going to abandon this rather stupid approach and use a simpler "one namespace per engine"-scheme. This change should (hopefully) be transparent for little scripts that don't have their own explicit namespaces. If your scripts use user-defined namespaces, I'll just assume you break this isolation intentionally (which is true to the meaning of namespaces, after all). If anybody would like to look into the classloader-based isolation, I'd happily to integrate this change (even if this means a severe startup-overhead for the creation of each engine-instance; it's simply the proper way to do it). For production (at least if you plan to have more than one active engine instance), I'd recommend to wait for either the namespace-based isolation or (should anybody get involved) the classloader-based approach. I'll reply to this thread again if one of these approaches is implemented.