空指針異常

Question

我正在寫一個簡單的IRC機器人，試圖瞭解更多關於Clojure的，使用標準的Java插座和一個循環讀取/分析數據，但我得到一個空指針時由於某種原因，我試圖在MOTD結束消息後發送JOIN消息。

這裏是我的代碼..

(use 'clojure.java.io 
'[clojure.string :as s :only (split)]) 

(def sock (java.net.Socket. "iris.archivesmc.com" 6667)) 

(def write-stream (writer sock)) 
(def read-stream (reader sock)) 

(defn write [message] 
    (.write write-stream (str message "\r\n")) 
    (println (str "-> " message)) 
    (.flush write-stream) 
) 

(defn parseMessage [buffer] 
    (if 
     (= (apply str (take-last 2 buffer)) "\r\n") 
     (do 
      (let [parts (split buffer #"\s")] 
       (println (s/replace buffer "\r\n" "")) 
       (when 
        (= (first parts) "PING") 
        ;; We need to PONG to this or we'll ping out 
        (write (str "PONG " (second parts))) 
       ) 
       (when 
        (= (apply str(take 1 (first parts))) ":") 
        ;; Message with a numerical prefix 
        ;; :server numeric our-nick message 
        (
         (if 
          (= (second parts) "376") 
          ;; MOTD end 
          ;; Join #clojure 
          (write "JOIN #clojure") ;; This errors for some reason 
         ) 
        ) 
       ) 
      ) 
      "" 
     ) 
     buffer 
    ) 
) 

(defn readLoop [] 
    (loop [buffer ""] 
     ;;(println (str "Looping.. -> " buffer)) 
     (let [nbuf (parseMessage buffer) 
       nchr (.read read-stream) ] 
      (if-not (= nchr -1) 
       (recur (str nbuf (char nchr))) 
      ) 
     ) 
    ) 
) 

(write "NICK gClojureTestBot") 
(write "USER Clojure Imma Bot :Clojure Testing Bot") 
(readLoop) 

這是我的輸出（與追溯等）

/usr/lib/jvm/jdk1.7.0_04/bin/java -Didea.launcher.port=7542 -Didea.launcher.bin.path=/home/gcoles/Downloads/idea-IC-117.418/bin -Dfile.encoding=UTF-8 -classpath /usr/lib/jvm/jdk1.7.0_04/jre/lib/resources.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/javaws.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/jfr.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/jsse.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/deploy.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/management-agent.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/jce.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/charsets.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/plugin.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/rt.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/ext/sunec.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/ext/sunjce_provider.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/ext/zipfs.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/ext/dnsns.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/ext/localedata.jar:/usr/lib/jvm/jdk1.7.0_04/jre/lib/ext/sunpkcs11.jar:/home/gcoles/IdeaProjects/ClojureBot/classes:/home/gcoles/clojure/clojure-1.4.0/clojure-1.4.0.jar:/home/gcoles/IdeaProjects/ClojureBot/src:/home/gcoles/IdeaProjects/ClojureBot/test:/home/gcoles/Downloads/idea-IC-117.418/lib/idea_rt.jar com.intellij.rt.execution.application.AppMain clojure.main /home/gcoles/IdeaProjects/ClojureBot/src/main.clj 
-> NICK gClojureTestBot 
-> USER Clojure Imma Bot :Clojure Testing Bot 
PING :5D2E1C22 
-> PONG :5D2E1C22 
:iris.archivesmc.com 001 gClojureTestBot :Welcome to the archivesmc.com IRC Network gClojureTestBot!~Clojure@213.190.134.190 
Exception in thread "main" java.lang.NullPointerException 
    at user$parseMessage.invoke(main.clj:35) 
    at user$readLoop.invoke(main.clj:49) 
    at user$eval10.invoke(main.clj:60) 
    at clojure.lang.Compiler.eval(Compiler.java:6511) 
    at clojure.lang.Compiler.load(Compiler.java:6952) 
    at clojure.lang.Compiler.loadFile(Compiler.java:6912) 
    at clojure.main$load_script.invoke(main.clj:283) 
    at clojure.main$script_opt.invoke(main.clj:343) 
    at clojure.main$main.doInvoke(main.clj:427) 
    at clojure.lang.RestFn.invoke(RestFn.java:408) 
    at clojure.lang.Var.invoke(Var.java:415) 
    at clojure.lang.AFn.applyToHelper(AFn.java:161) 
    at clojure.lang.Var.applyTo(Var.java:532) 
    at clojure.main.main(main.java:37) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:601) 
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120) 

Process finished with exit code 1 

我覺得這很奇怪，因爲以write以前調用工作。再一次，作爲Clojure（和Java）noob，我可能做了一些愚蠢的事情。

任何人有任何想法？

編輯：如果它的事項，我使用的Java 7和Clojure的1.4.0

Answer 1

的問題是與下面的代碼塊..

  (when 
       (= (apply str(take 1 (first parts))) ":") 
       ;; Message with a numerical prefix 
       ;; :server numeric our-nick message 
       (
        (if 
         (= (second parts) "376") 
         ;; MOTD end 
         ;; Join #clojure 
         (write "JOIN #clojure") ;; This errors for some reason 
        ) 
       ) 
      ) 

具體來說，()各地(if)聲明翻了一番。太多的括號。刪除額外的問題解決了問題。