Question

使用Clojure proxies时，传递给代理的fns应覆盖现有方法，还是与super.method()一起调用？

在以下代码中，RequestHandler.get（）与代理get []一起被调用。

;see: http://github.com/paulosuzart/JTornado
(ns org.ctornadoweb)
(import '(org.jtornadoweb Web$RequestHandler))
(import '(org.jtornadoweb HttpServer Web$Application))


(let [myHandler (proxy [Web$RequestHandler] [] 
                  (get [] 
                    (.write "Hi CLJ"))
                  (post []
                    (.write "POST")))]

(.listen
  (HttpServer.  
    (.add (Web$Application.) "/" (class myHandler))
    false nil false) 8089))

编译/继承版本也是如此：

; Starts a JTornado HTTP Server and a sample RequestHandler.
; Bit verbose due to compilation directives. Recommendation is to generate 
; a set of macros to hide this.
(ns org.ctornadoweb
; Compiled and implements a static main method to start the server
  (:import (org.jtornadoweb HttpServer)
           (org.jtornadoweb.Web$Application)
           (org.jtornadoweb.Web$RequestHandler))
  (:gen-class :prefix "server-"))

(gen-class
 :name org.ctornadoweb.MyHandler
 :extends org.jtornadoweb.Web$RequestHandler
 :prefix "do")

(defn do-get [this]
  "Handles the HTTP GET method"
  (.write "hello clojure"))
(defn do-post [this]
  "Handles the HTTP POST method"
  (.write (.getArgument "name" "default" false)))


(defn server-main []
  "main method"
 (.listen
  (org.jtornadoweb.HttpServer.
   (.add (org.jtornadoweb.Web$Application.) "/" org.ctornadoweb.MyHandler)
     false nil false) 8089))

;use (compile 'org.ctornadoweb)

跟踪显示调用代理，然后是super.get，抛出（默认情况下）异常。

HTTP 405: Method Not Allowed 
    at org.jtornadoweb.Web$RequestHandler.get(Web.java:72)
    at org.ctornadoweb.proxy$org.jtornadoweb.Web$RequestHandler$0.get(Unknown Source)

我试图找到一些关于Clojure Proxies实际行为的文字。有人能帮忙吗？

Answer 1

不，不会自动调用super方法，但您可以使用proxy-super显式调用它。

以下测试用例表明事情正常：

user=> (def foo 
         (proxy [java.util.ArrayList] [] 
           (clear [] (println "not clearing"))))
#'user/foo
user=> (.size foo)
0
user=> (.add foo "hi")
true
user=> (.add foo "bye")
true
user=> (.size foo)
2
user=> (.clear foo)
not clearing
nil
user=> (.size foo)
2

如果调用super.clear()，则大小将显示为0.

Clojure代理总是调用super.method（）吗？

1 个答案: