How do I implement a Java interface in Clojure

Question

How do I create a Clojure object that implements this interface and then gets called from Java code?

public interface Doer {
   public String doSomethin(Stri         


        

Answer 1

With proxy

See the proxy macro. Clojure Docs have some examples. It's also covered on Java Interop page.

(proxy [Doer] []
  (doSomethin [input]
    (str input " went through proxy")))

proxy returns an object implementing Doer. Now, to access it in Java you have to use gen-class to make your Clojure code callable from Java. It's covered in an answer to the "Calling clojure from java" question.

With gen-class

(ns doer-clj
  (:gen-class
    :name DoerClj
    :implements [Doer]
    :methods [[doSomethin [String] String]]))

(defn -doSomethin
  [_ input]
  (str input " went through Clojure"))

Now save it as doer_clj.clj, mkdir classes and compile it by calling in your REPL (require 'doer-clj) (compile 'doer-clj). You should find DoerClj.class ready to be used from Java in classes directory