Is shipping a Clojure desktop app realistic?

Question

I'm currently shipping a desktop Java application. It is a plain old Java 5 Java / Swing app and so far everything worked nicely. Java 5 was targetted because some users were on OS X version / computers that shall never have Java 6 (we may lift this limitation soon and switch to a newer Java and simply abandoning my users stuck with Java 5).

I'm quickly getting up to speed with Clojure but I haven't really done lots of Clojure-to-Java and Java-to-Clojure yet and I was wondering if it was realistic to ship a Clojure desktop application instead of a Java application?

The application I'm shipping is currently about 12 MB with all the .jar so adding Clojure doesn't seen to be too much of an issue.

My plan would be to have Clojure call Java APIs: my application is already divided in several independent jars.

If I understand correctly calling Clojure from Java is harder than calling Java code from Clojure which is why I'd basically rewrite all the UI (part of the UI, mixing Swing components and self-made BufferedImages needs to be rewritten anyway due to the rise of retina display), and do all the 'wiring' from Clojure.

So that's the problem I'm facing: is it realistic to ship a Clojure desktop app? (it certainly doesn't seem to be very widespread but then shipping plain Java desktop apps ain't that common either and I'm doing it anyway)

Technically, what would need to be done? (compared to shipping a Java app)

Answer 1

Yes, it is entirely realistic - not many people seem to be doing it yet but I think that is only a matter of time (Clojure is pretty new after all!)

I've personally written an open-source game in Clojure which runs as a Swing application (https://github.com/mikera/ironclad) so have some experiences to share which may be useful.

• On average you probably want to have Clojure call into Java APIs. This is mostly common sense - Java has all the great libraries, Clojure is the more productive language for gluing things together.
• You may want to write a Java-based "loader" with a main(...) method that launches the Clojure part of the code. Among other things, this means that you won't have to AOT compile your Clojure code. Example code here: https://github.com/mikera/ironclad/blob/master/src/main/java/ic/IronClad.java
• You will probably want to do things like throw up a splash screen while your application initialises to allow for the extra startup time loading/compiling Clojure code. It probably adds 1-2 seconds to a typical app startup time, which is enough that your user will probably appreciate some feedback. If you are clever, you can actually throw up the whole UI while other stuff loads in the background but this requires some care and might test your concurrency kung-fu :-)
• You can mix Java and Clojure relatively freely since they can call backwards and forwards fairly transparently. The only complication if you want Java to call Clojure is that Java likes to know the class / interface it is calling at compile time. A good option is to have Clojure code dynamically implement an aleady-compiled Java interface via reify.
• I've found it pretty easy to develop and package an app in a single jar containing both Clojure and Java code using Eclipse/Maven. The Clojure code can simply be put in src/main/resources and gets loaded / compiled at runtime.
• You can use Clojure GUI wrappers like seesaw if you like. It seems to be pretty good. I decided against using it, mainly because I wanted to do some fiddly things with Swing directly and didn't feel that I needed an extra layer of abstraction.