A very simple example showing how to integrate JRuby, Rails and Clojure:
There are two clojure source files in app/clojure: utilities/support.clj and utilities/ClojureTest.clj. I ended up with these as I played around with namespaces. support.clj simply defines a single function in the utilities.support namespace.
ClojureTest.clj references the clojure.support namespace and defines a namespace utilities.ClojureTest. This is mapped (via genclass) to a Java class ClojureTest in the utilities namespace. ClojureTest exposes a single function (stringLength); think of this as the API your Clojure lib exposes to the JRuby world.
There's a simple rake task in lib/tasks/clojure.rake that has two targets: rake clojure:compile will compile the stuff in app/clojure to the tmp/target/classes directory. rake clojure:jar (which depends on clojure:compile) creates a jar file in the lib directory for each top-level directory in app/clojure (e.g. utilities.jar)
In the controller clojure_test_controller.rb, the function ClojureTest::string_length is invoked. If Rails can't resolve a module, it ends up looking for a .rb file in lib that has the corresponding name in lower case and with underscores. lib/clojure_test.rb simply does a java_import to create a module that contains the functions defined in the ClojureTest class.
Interesting things that one might do:
- Define more rake tasks for Clojure, e.g. for a REPL, for Swank etc. This should probably be a separate project.
- Show some more sample interactions, e.g. send-off to an agent from within a controller or access to a Clojure persistent data structure from JRuby
- Show how to access JRuby from Clojure, e.g. to access models