gistfile1.clj

;; I am trying to parse a nested Java object (a Google Protobuffer), which comes in as raw bytes. To parse the bytes,
;; I have to know the class of the object. Fortunately, for the innermost object, the class is specified as a field in
;; an outer object. The parsing function is specified as a static method on the class, with expected use like:
;; (com.url.place.Type$SubType/parseFrom (.getByteArrayFromInnerObj inner-obj))

;; What I'm trying to do is something like this:

(def decl-obj-map
  {:type-subtype Type$SubType})

(defn call-fn
  [class n-args method]
  (let [o (gensym)
        args (repeatedly n-args gensym)
        assure-symbol (fn [thing] (if (symbol? thing) thing (symbol thing)))
        method (assure-symbol method)]
    (eval
     `(fn [~o ~@args]
        (. ~(with-meta o {:tag class})
           (~method ~@args))))))

(def parse-func (call-fn (:type-subtype decl-obj-map) 0 "parseFrom")

(parse-func (.getByteArrayFromInnerObj inner-obj)) ;; This call explodes.

Worth pointing out that parseFrom dispatches on both arity and type; there are something like six different parseFrom methods on this object.

call-fn works well with public, non-static methods; it explodes on static methods. I've also been trying http://clojuredocs.org/clojure_contrib/clojure.contrib.reflect/call-method, which throws IllegalArgumentException array element type mismatch java.lang.reflect.Array.set (Array.java:-2) Which I do not at all understand.