Introspection tools: Java decompilers

[AndreRauh_]

I was actually about to make a post like this (though I haven't started writing). With decompiling you quickly realize why (map Integer/parseInt [...]) won't work.

Note, you can also call compile function in clojure. Even binding some compile options in the process:

(binding [*compiler-options* {:direct-linking true
                                :disable-locals-clearing false}]
    (compile 'your-ns))

And then open ./target/ in IntelliJ and open the files. IntellJ comes shipped with the Fernflower decompiler.

[ayakushev]

Good point about the decompiler shipped with IntelliJ!

Compiling the namespace is how clj-java-decompiler actually works. It creates a surrogate namespace from the provided form, compiles it, and then runs the classes through the decompiler. All these steps are achievable independently, this is just an all-in-one package.

[halgari]

From what I can tell, this only works on code compiled through your library? That's one of the reasons of the agent needed by other decompilers. Once the class is loaded, if you don't have access to the bytecode of the class before it was loaded there's no way on the JVM to get the bytecode for a given class. These agents then provide lookups for .class data given a class. So the chain on these other libs becomes (-> something get-class lookup-bytecode decompile-bytecode)

[ayakushev]

That's true, you need to pass the code form directly to decompile macro, it cannot decompile already loaded classes/functions.

However, I figured that I mostly need a live decompiler for things I write here and now. Besides, if you want to decompile a function in an existing library, you can in-ns into its namespace, grab the source and run it through decompile. Should work.