public void OnIdleStateChange(AccSession arg0, int arg1) {
}
 
public void OnInstanceChange(AccSession arg0, AccInstance arg1, AccInstance arg2, AccInstanceProp arg3) {
}
 
public void OnLookupUsersResult(AccSession arg0, String[] arg1, int arg2, AccResult arg3, AccUser[] arg4) {
}
 
public void OnSearchDirectoryResult(AccSession arg0, int arg1, AccResult arg2, AccDirEntry arg3) {
}
 
// ... go on like this for pages

(defmacro auto-proxy [interfaces variables & args]
  (let [defined (set (map #(str (first %)) args))
        names (fn [i] (map #(.getName %) (.getMethods i)))
        all-names (into #{} (apply concat (map names (map resolve interfaces))))
        undefined (difference all-names defined) 
        auto-gen (map (fn [x] `(~(symbol x) [& ~'args])) undefined)]
    `(proxy ~interfaces ~variables ~@args ~@auto-gen)))

(defn create-aim-proxy []
  (auto-proxy [com.aol.acc.AccEvents] []
     (OnImReceived [session imSession participant im] 
        (handle-im session imSession participant im))
     (OnStateChange [arg0 arg1 arg2]
        (handle-state-change arg0 arg1 arg2))))

7 Responses to “Snippet: Automatic Proxy Creation in Clojure”

1. Duncan (August 23rd, 2009 at 9:14 am )
   

   Why do you need to do this, doesn’t the proxy form already do this for you?

   “If a method fn is not provided for an interface method, an UnsupportedOperationException will be thrown should it be called.”

   http://clojure.org/java_interop#toc25

2. tim (August 23rd, 2009 at 1:10 pm )
   

   @Duncan: I didn’t want it to throw an exception, I wanted it to just have an empty default implementation. Since it was being invoked as a callback from the API, I didn’t even have an intervening level in which I could put a try statement.

3. Jetpack (January 4th, 2010 at 8:14 am )
   

   Tim, this is a very useful macro for me and I bet for plenty of others that want to migrate from Java to Clojure. Have you submitted it to Rich for inclusion in clojure-contrib or core?

4. tim (January 15th, 2010 at 9:28 am )
   

   @Jetpack: Yah, I’d be interested in that, but last time I looked it wasn’t obvious how to go about submitting stuff. I’ll definitely take a look.

5. Jetpack (March 9th, 2010 at 6:11 am )
   

   Tim, I’m trying to extend a class as well as implement an interface in the same proxy. Would you have an idea how I could do this with your auto-proxy macro? Simply adding the extended class to the auto-proxy arguments gives me an excpetion: “java.lang.IncompatibleClassChangeError: Implementing class”.

6. Jetpack (March 9th, 2010 at 6:24 am )
   

   Got the solution from #clojure: the extended class name needs to be put at the front of the interfaces argument of the macro. works like a charm.

   Again, in my opinion this macro would be a very useful addition to clojure-contrib or core.

7. Automatically create wrapper object in Clojure | LispCast (March 26th, 2010 at 7:38 am )
   

   [...] Brool shared a macro for creating a proxy that doesn’t throw exceptions for methods that aren’t define. It is called autoproxy. I [...]

Leave a Reply