19

I want to take working Clojure source code files (.clj) and convert them into the equivalent java source code files (.java) automatically. I'm wondering what the best way to do this is or if it is even possible. The converted java source code would need to be acceptable enough.

Improve this question
5
  • 2
    It's definitely possible, because Clojure compiles to JVM bytecode, and there are bytecode-to-Java decompilers. But one suspects and hopes there's a more direct route that will produce dramatically higher-quality code... Commented Jul 2, 2011 at 16:11
  • 3
    Have a look at: georgejahad.com/clojure/clojureDecompiled.html Commented Jul 2, 2011 at 16:11
  • Yes, I mean is it possible to produce the Java source with any readability. Commented Jul 2, 2011 at 16:22
  • 1
    note that you may end up depending on the clojure runtime library anyway. Commented Jul 2, 2011 at 16:35
  • 1
    It might be possible with a lot of effort, but I'd strongly recommend against the idea - auto translated code is generally horrible and unmaintainable by humans. It will be even worse in Clojure->Java because Clojure has a lot of constructs that are not easy to express in Java (macros? eval?). You have been warned! Commented Jul 2, 2011 at 20:20

4 Answers 4

Reset to default
18

Your best bet, as others have pointed out, would be to use a bytecode decompiler. You'll still need the clojure classes though. But, more importantly, if your goal is to generate Java code that needs to be handled by Java programmers, it is very unlikely that you'll succeed.

Clojure is not just "java with a different syntax". Its language constructs are so different from java that many things that are idiomatic Clojure will look very foreign in Java.

Even if your Java code would look more or less readable, your Java developers would get incredibly frustrated. They'd essentially still need to program Lisp but use Java syntax and very strange constructs: It'll be a mess.

If you're looking to use Clojure in a team of Java developers, I'd try to develop and package your Clojure code as a jar with a well defined java API. The Java developers would be happy, because it's just another java library, and you'll be happy because you'll write proper Clojure code.

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

9

I would try generating .class file from .clj and then decompiling it to .java with a decompiler e.g. JAD.

Improve this answer

1 Comment

Also keep in mind that the decompiled code will depend on Clojures classes. So you will not get "pure" Java code. It's probably the best solution though.
9

The Clojure debugging toolkit is an excellent tool for digging into compiled Clojure code and it demonstrates some of the ways Clojure's classes differ from classes produced from java source. It would be difficult for instance to write java code to represent Clojures closures for instance (though it's possible)

Clojure produces byte codes that cannot be produced by compiling any java program, so a general solution is not possible. Specifically Clojure nulls out arguments (in the calling frame) before making recursive calls. Since you are starting from source and not .class files you should be able to get close enough provided you don't try to guarantee that the java code will produce the exact same behavior. Clojure prevents some memory leaks in recursion that will be really hard to avoid in the equivalent java code.

"The purpose of this code is to null out the arguments to prevent 'holding the head' in case of a recursive function call. " from George Jahad's talk on decompiling clojure classes. http://georgejahad.com/clojure/clojureDecompiled.html

Improve this answer

Comments

5

I am not intimately familiar with Clojure but note that you in general can read in a Lisp program and treat it as a datastructure, which is most likely better than handling the compiled Clojure code as this strongly depends on the Clojure runtime.

If this is for your own programs then you can probably live with a very small subset of full Clojure and that can you probably handle yourself with a small program generator.

Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.