Java example source code file (main.clj)

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Java - Java tags/keywords

clojure, compilerexception, crlf, default, linenumberingpushbackreader, object, print, returns, run, stacktraceelement, the, throwable, warning

The main.clj Java example source code

;; Copyright (c) Rich Hickey All rights reserved. The use and
;; distribution terms for this software are covered by the Eclipse Public
;; License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) which can be found
;; in the file epl-v10.html at the root of this distribution. By using this
;; software in any fashion, you are agreeing to be bound by the terms of
;; this license. You must not remove this notice, or any other, from this
;; software.

;; Originally contributed by Stephen C. Gilardi

(ns ^{:doc "Top-level main function for Clojure REPL and scripts."
       :author "Stephen C. Gilardi and Rich Hickey"}
  clojure.main
  (:refer-clojure :exclude [with-bindings])
  (:import (clojure.lang Compiler Compiler$CompilerException
                         LineNumberingPushbackReader RT))
  ;;(:use [clojure.repl :only (demunge root-cause stack-element-str)])
  )

(declare main)

;;;;;;;;;;;;;;;;;;; redundantly copied from clojure.repl to avoid dep ;;;;;;;;;;;;;;
#_(defn root-cause [x] x)
#_(defn stack-element-str
  "Returns a (possibly unmunged) string representation of a StackTraceElement"
  {:added "1.3"}
  [^StackTraceElement el]
  (.getClassName el))

(defn demunge
  "Given a string representation of a fn class,
  as in a stack trace element, returns a readable version."
  {:added "1.3"}
  [fn-name]
  (clojure.lang.Compiler/demunge fn-name))

(defn root-cause
  "Returns the initial cause of an exception or error by peeling off all of
  its wrappers"
  {:added "1.3"}
  [^Throwable t]
  (loop [cause t]
    (if (and (instance? clojure.lang.Compiler$CompilerException cause)
             (not= (.source ^clojure.lang.Compiler$CompilerException cause) "NO_SOURCE_FILE"))
      cause
      (if-let [cause (.getCause cause)]
        (recur cause)
        cause))))

(defn stack-element-str
  "Returns a (possibly unmunged) string representation of a StackTraceElement"
  {:added "1.3"}
  [^StackTraceElement el]
  (let [file (.getFileName el)
        clojure-fn? (and file (or (.endsWith file ".clj")
                                  (.endsWith file ".cljc")
                                  (= file "NO_SOURCE_FILE")))]
    (str (if clojure-fn?
           (demunge (.getClassName el))
           (str (.getClassName el) "." (.getMethodName el)))
         " (" (.getFileName el) ":" (.getLineNumber el) ")")))
;;;;;;;;;;;;;;;;;;; end of redundantly copied from clojure.repl to avoid dep ;;;;;;;;;;;;;;


(defmacro with-bindings
  "Executes body in the context of thread-local bindings for several vars
  that often need to be set!: *ns* *warn-on-reflection* *math-context*
  *print-meta* *print-length* *print-level* *compile-path*
  *command-line-args* *1 *2 *3 *e"
  [& body]
  `(binding [*ns* *ns*
             *warn-on-reflection* *warn-on-reflection*
             *math-context* *math-context*
             *print-meta* *print-meta*
             *print-length* *print-length*
             *print-level* *print-level*
             *data-readers* *data-readers*
             *default-data-reader-fn* *default-data-reader-fn*
             *compile-path* (System/getProperty "clojure.compile.path" "classes")
             *command-line-args* *command-line-args*
             *unchecked-math* *unchecked-math*
             *assert* *assert*
             *1 nil
             *2 nil
             *3 nil
             *e nil]
     ~@body))

(defn repl-prompt
  "Default :prompt hook for repl"
  []
  (printf "%s=> " (ns-name *ns*)))

(defn skip-if-eol
  "If the next character on stream s is a newline, skips it, otherwise
  leaves the stream untouched. Returns :line-start, :stream-end, or :body
  to indicate the relative location of the next character on s. The stream
  must either be an instance of LineNumberingPushbackReader or duplicate
  its behavior of both supporting .unread and collapsing all of CR, LF, and
  CRLF to a single \\newline."
  [s]
  (let [c (.read s)]
    (cond
     (= c (int \newline)) :line-start
     (= c -1) :stream-end
     :else (do (.unread s c) :body))))

(defn skip-whitespace
  "Skips whitespace characters on stream s. Returns :line-start, :stream-end,
  or :body to indicate the relative location of the next character on s.
  Interprets comma as whitespace and semicolon as comment to end of line.
  Does not interpret #! as comment to end of line because only one
  character of lookahead is available. The stream must either be an
  instance of LineNumberingPushbackReader or duplicate its behavior of both
  supporting .unread and collapsing all of CR, LF, and CRLF to a single
  \\newline."
  [s]
  (loop [c (.read s)]
    (cond
     (= c (int \newline)) :line-start
     (= c -1) :stream-end
     (= c (int \;)) (do (.readLine s) :line-start)
     (or (Character/isWhitespace (char c)) (= c (int \,))) (recur (.read s))
     :else (do (.unread s c) :body))))

(defn repl-read
  "Default :read hook for repl. Reads from *in* which must either be an
  instance of LineNumberingPushbackReader or duplicate its behavior of both
  supporting .unread and collapsing all of CR, LF, and CRLF into a single
  \\newline. repl-read:
    - skips whitespace, then
      - returns request-prompt on start of line, or
      - returns request-exit on end of stream, or
      - reads an object from the input stream, then
        - skips the next input character if it's end of line, then
        - returns the object."
  [request-prompt request-exit]
  (or ({:line-start request-prompt :stream-end request-exit}
       (skip-whitespace *in*))
      (let [input (read {:read-cond :allow} *in*)]
        (skip-if-eol *in*)
        input)))

(defn repl-exception
  "Returns the root cause of throwables"
  [throwable]
  (root-cause throwable))

(defn repl-caught
  "Default :caught hook for repl"
  [e]
  (let [ex (repl-exception e)
        tr (.getStackTrace ex)
        el (when-not (zero? (count tr)) (aget tr 0))]
    (binding [*out* *err*]
      (println (str (-> ex class .getSimpleName)
                    " " (.getMessage ex) " "
                    (when-not (instance? clojure.lang.Compiler$CompilerException ex)
                      (str " " (if el (stack-element-str el) "[trace missing]"))))))))

(def ^{:doc "A sequence of lib specs that are applied to `require`
by default when a new command-line REPL is started."} repl-requires
  '[[clojure.repl :refer (source apropos dir pst doc find-doc)]
    [clojure.java.javadoc :refer (javadoc)]
    [clojure.pprint :refer (pp pprint)]])

(defmacro with-read-known
  "Evaluates body with *read-eval* set to a \"known\" value,
   i.e. substituting true for :unknown if necessary."
  [& body]
  `(binding [*read-eval* (if (= :unknown *read-eval*) true *read-eval*)]
     ~@body))

(defn repl
  "Generic, reusable, read-eval-print loop. By default, reads from *in*,
  writes to *out*, and prints exception summaries to *err*. If you use the
  default :read hook, *in* must either be an instance of
  LineNumberingPushbackReader or duplicate its behavior of both supporting
  .unread and collapsing CR, LF, and CRLF into a single \\newline. Options
  are sequential keyword-value pairs. Available options and their defaults:

     - :init, function of no arguments, initialization hook called with
       bindings for set!-able vars in place.
       default: #()

     - :need-prompt, function of no arguments, called before each
       read-eval-print except the first, the user will be prompted if it
       returns true.
       default: (if (instance? LineNumberingPushbackReader *in*)
                  #(.atLineStart *in*)
                  #(identity true))

     - :prompt, function of no arguments, prompts for more input.
       default: repl-prompt

     - :flush, function of no arguments, flushes output
       default: flush

     - :read, function of two arguments, reads from *in*:
         - returns its first argument to request a fresh prompt
           - depending on need-prompt, this may cause the repl to prompt
             before reading again
         - returns its second argument to request an exit from the repl
         - else returns the next object read from the input stream
       default: repl-read

     - :eval, function of one argument, returns the evaluation of its
       argument
       default: eval

     - :print, function of one argument, prints its argument to the output
       default: prn

     - :caught, function of one argument, a throwable, called when
       read, eval, or print throws an exception or error
       default: repl-caught"
  [& options]
  (let [cl (.getContextClassLoader (Thread/currentThread))]
    (.setContextClassLoader (Thread/currentThread) (clojure.lang.DynamicClassLoader. cl)))
  (let [{:keys [init need-prompt prompt flush read eval print caught]
         :or {init        #()
              need-prompt (if (instance? LineNumberingPushbackReader *in*)
                            #(.atLineStart ^LineNumberingPushbackReader *in*)
                            #(identity true))
              prompt      repl-prompt
              flush       flush
              read        repl-read
              eval        eval
              print       prn
              caught      repl-caught}}
        (apply hash-map options)
        request-prompt (Object.)
        request-exit (Object.)
        read-eval-print
        (fn []
          (try
            (let [read-eval *read-eval*
                  input (with-read-known (read request-prompt request-exit))]
             (or (#{request-prompt request-exit} input)
                 (let [value (binding [*read-eval* read-eval] (eval input))]
                   (print value)
                   (set! *3 *2)
                   (set! *2 *1)
                   (set! *1 value))))
           (catch Throwable e
             (caught e)
             (set! *e e))))]
    (with-bindings
     (try
      (init)
      (catch Throwable e
        (caught e)
        (set! *e e)))
     (prompt)
     (flush)
     (loop []
       (when-not 
       	 (try (identical? (read-eval-print) request-exit)
	  (catch Throwable e
	   (caught e)
	   (set! *e e)
	   nil))
         (when (need-prompt)
           (prompt)
           (flush))
         (recur))))))

(defn load-script
  "Loads Clojure source from a file or resource given its path. Paths
  beginning with @ or @/ are considered relative to classpath."
  [^String path]
  (if (.startsWith path "@")
    (RT/loadResourceScript
     (.substring path (if (.startsWith path "@/") 2 1)))
    (Compiler/loadFile path)))

(defn- init-opt
  "Load a script"
  [path]
  (load-script path))

(defn- eval-opt
  "Evals expressions in str, prints each non-nil result using prn"
  [str]
  (let [eof (Object.)
        reader (LineNumberingPushbackReader. (java.io.StringReader. str))]
      (loop [input (with-read-known (read reader false eof))]
        (when-not (= input eof)
          (let [value (eval input)]
            (when-not (nil? value)
              (prn value))
            (recur (with-read-known (read reader false eof))))))))

(defn- init-dispatch
  "Returns the handler associated with an init opt"
  [opt]
  ({"-i"     init-opt
    "--init" init-opt
    "-e"     eval-opt
    "--eval" eval-opt} opt))

(defn- initialize
  "Common initialize routine for repl, script, and null opts"
  [args inits]
  (in-ns 'user)
  (set! *command-line-args* args)
  (doseq [[opt arg] inits]
    ((init-dispatch opt) arg)))

(defn- main-opt
  "Call the -main function from a namespace with string arguments from
  the command line."
  [[_ main-ns & args] inits]
  (with-bindings
    (initialize args inits)
    (apply (ns-resolve (doto (symbol main-ns) require) '-main) args)))

(defn- repl-opt
  "Start a repl with args and inits. Print greeting if no eval options were
  present"
  [[_ & args] inits]
  (when-not (some #(= eval-opt (init-dispatch (first %))) inits)
    (println "Clojure" (clojure-version)))
  (repl :init (fn []
                (initialize args inits)
                (apply require repl-requires)))
  (prn)
  (System/exit 0))

(defn- script-opt
  "Run a script from a file, resource, or standard in with args and inits"
  [[path & args] inits]
  (with-bindings
    (initialize args inits)
    (if (= path "-")
      (load-reader *in*)
      (load-script path))))

(defn- null-opt
  "No repl or script opt present, just bind args and run inits"
  [args inits]
  (with-bindings
    (initialize args inits)))

(defn- help-opt
  "Print help text for main"
  [_ _]
  (println (:doc (meta (var main)))))

(defn- main-dispatch
  "Returns the handler associated with a main option"
  [opt]
  (or
   ({"-r"     repl-opt
     "--repl" repl-opt
     "-m"     main-opt
     "--main" main-opt
     nil      null-opt
     "-h"     help-opt
     "--help" help-opt
     "-?"     help-opt} opt)
   script-opt))

(defn- legacy-repl
  "Called by the clojure.lang.Repl.main stub to run a repl with args
  specified the old way"
  [args]
  (println "WARNING: clojure.lang.Repl is deprecated.
Instead, use clojure.main like this:
java -cp clojure.jar clojure.main -i init.clj -r args...")
  (let [[inits [sep & args]] (split-with (complement #{"--"}) args)]
    (repl-opt (concat ["-r"] args) (map vector (repeat "-i") inits))))

(defn- legacy-script
  "Called by the clojure.lang.Script.main stub to run a script with args
  specified the old way"
  [args]
  (println "WARNING: clojure.lang.Script is deprecated.
Instead, use clojure.main like this:
java -cp clojure.jar clojure.main -i init.clj script.clj args...")
  (let [[inits [sep & args]] (split-with (complement #{"--"}) args)]
    (null-opt args (map vector (repeat "-i") inits))))

(defn main
  "Usage: java -cp clojure.jar clojure.main [init-opt*] [main-opt] [arg*]

  With no options or args, runs an interactive Read-Eval-Print Loop

  init options:
    -i, --init path     Load a file or resource
    -e, --eval string   Evaluate expressions in string; print non-nil values

  main options:
    -m, --main ns-name  Call the -main function from a namespace with args
    -r, --repl          Run a repl
    path                Run a script from a file or resource
    -                   Run a script from standard input
    -h, -?, --help      Print this help message and exit

  operation:

    - Establishes thread-local bindings for commonly set!-able vars
    - Enters the user namespace
    - Binds *command-line-args* to a seq of strings containing command line
      args that appear after any main option
    - Runs all init options in order
    - Calls a -main function or runs a repl or script if requested

  The init options may be repeated and mixed freely, but must appear before
  any main option. The appearance of any eval option before running a repl
  suppresses the usual repl greeting message: \"Clojure ~(clojure-version)\".

  Paths may be absolute or relative in the filesystem or relative to
  classpath. Classpath-relative paths have prefix of @ or @/"
  [& args]
  (try
   (if args
     (loop [[opt arg & more :as args] args inits []]
       (if (init-dispatch opt)
         (recur more (conj inits [opt arg]))
         ((main-dispatch opt) args inits)))
     (repl-opt nil nil))
   (finally 
     (flush))))