Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

342 lines (291 sloc) 12.218 kb
;;; json.clj: JavaScript Object Notation (JSON) parser/writer
;; by Stuart Sierra, http://stuartsierra.com/
;; January 30, 2010
;; Copyright (c) Stuart Sierra, 2010. 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.
(ns ^{:author "Stuart Sierra"
:doc "JavaScript Object Notation (JSON) parser/writer.
See http://www.json.org/
To write JSON, use json-str, write-json, or write-json.
To read JSON, use read-json."}
clojure.contrib.json
(:use [clojure.contrib.pprint :only (write formatter-out)]
[clojure.contrib.string :only (as-str)])
(:import (java.io PrintWriter PushbackReader StringWriter
StringReader Reader EOFException)))
;;; JSON READER
(declare read-json-reader)
(defn- read-json-array [^PushbackReader stream keywordize?]
;; Expects to be called with the head of the stream AFTER the
;; opening bracket.
(loop [i (.read stream), result (transient [])]
(let [c (char i)]
(cond
(= i -1) (throw (EOFException. "JSON error (end-of-file inside array)"))
(Character/isWhitespace c) (recur (.read stream) result)
(= c \,) (recur (.read stream) result)
(= c \]) (persistent! result)
:else (do (.unread stream (int c))
(let [element (read-json-reader stream keywordize? true nil)]
(recur (.read stream) (conj! result element))))))))
(defn- read-json-object [^PushbackReader stream keywordize?]
;; Expects to be called with the head of the stream AFTER the
;; opening bracket.
(loop [i (.read stream), key nil, result (transient {})]
(let [c (char i)]
(cond
(= i -1) (throw (EOFException. "JSON error (end-of-file inside object)"))
(Character/isWhitespace c) (recur (.read stream) key result)
(= c \,) (recur (.read stream) nil result)
(= c \:) (recur (.read stream) key result)
(= c \}) (if (nil? key)
(persistent! result)
(throw (Exception. "JSON error (key missing value in object)")))
:else (do (.unread stream i)
(let [element (read-json-reader stream keywordize? true nil)]
(if (nil? key)
(if (string? element)
(recur (.read stream) element result)
(throw (Exception. "JSON error (non-string key in object)")))
(recur (.read stream) nil
(assoc! result (if keywordize? (keyword key) key)
element)))))))))
(defn- read-json-hex-character [^PushbackReader stream]
;; Expects to be called with the head of the stream AFTER the
;; initial "\u". Reads the next four characters from the stream.
(let [digits [(.read stream)
(.read stream)
(.read stream)
(.read stream)]]
(when (some neg? digits)
(throw (EOFException. "JSON error (end-of-file inside Unicode character escape)")))
(let [chars (map char digits)]
(when-not (every? #{\0 \1 \2 \3 \4 \5 \6 \7 \8 \9 \a \b \c \d \e \f \A \B \C \D \E \F}
chars)
(throw (Exception. "JSON error (invalid hex character in Unicode character escape)")))
(char (Integer/parseInt (apply str chars) 16)))))
(defn- read-json-escaped-character [^PushbackReader stream]
;; Expects to be called with the head of the stream AFTER the
;; initial backslash.
(let [c (char (.read stream))]
(cond
(#{\" \\ \/} c) c
(= c \b) \backspace
(= c \f) \formfeed
(= c \n) \newline
(= c \r) \return
(= c \t) \tab
(= c \u) (read-json-hex-character stream))))
(defn- read-json-quoted-string [^PushbackReader stream]
;; Expects to be called with the head of the stream AFTER the
;; opening quotation mark.
(let [buffer (StringBuilder.)]
(loop [i (.read stream)]
(let [c (char i)]
(cond
(= i -1) (throw (EOFException. "JSON error (end-of-file inside string)"))
(= c \") (str buffer)
(= c \\) (do (.append buffer (read-json-escaped-character stream))
(recur (.read stream)))
:else (do (.append buffer c)
(recur (.read stream))))))))
(defn- read-json-reader
([^PushbackReader stream keywordize? eof-error? eof-value]
(loop [i (.read stream)]
(let [c (char i)]
(cond
;; Handle end-of-stream
(= i -1) (if eof-error?
(throw (EOFException. "JSON error (end-of-file)"))
eof-value)
;; Ignore whitespace
(Character/isWhitespace c) (recur (.read stream))
;; Read numbers, true, and false with Clojure reader
(#{\- \0 \1 \2 \3 \4 \5 \6 \7 \8 \9} c)
(do (.unread stream i)
(read stream true nil))
;; Read strings
(= c \") (read-json-quoted-string stream)
;; Read null as nil
(= c \n) (let [ull [(char (.read stream))
(char (.read stream))
(char (.read stream))]]
(if (= ull [\u \l \l])
nil
(throw (Exception. (str "JSON error (expected null): " c ull)))))
;; Read true
(= c \t) (let [rue [(char (.read stream))
(char (.read stream))
(char (.read stream))]]
(if (= rue [\r \u \e])
true
(throw (Exception. (str "JSON error (expected true): " c rue)))))
;; Read false
(= c \f) (let [alse [(char (.read stream))
(char (.read stream))
(char (.read stream))
(char (.read stream))]]
(if (= alse [\a \l \s \e])
false
(throw (Exception. (str "JSON error (expected false): " c alse)))))
;; Read JSON objects
(= c \{) (read-json-object stream keywordize?)
;; Read JSON arrays
(= c \[) (read-json-array stream keywordize?)
:else (throw (Exception. (str "JSON error (unexpected character): " c))))))))
(defprotocol Read-JSON-From
(read-json-from [input keywordize? eof-error? eof-value]
"Reads one JSON value from input String or Reader.
If keywordize? is true, object keys will be converted to keywords.
If eof-error? is true, empty input will throw an EOFException; if
false EOF will return eof-value. "))
(extend-protocol
Read-JSON-From
String
(read-json-from [input keywordize? eof-error? eof-value]
(read-json-reader (PushbackReader. (StringReader. input))
keywordize? eof-error? eof-value))
PushbackReader
(read-json-from [input keywordize? eof-error? eof-value]
(read-json-reader input
keywordize? eof-error? eof-value))
Reader
(read-json-from [input keywordize? eof-error? eof-value]
(read-json-reader (PushbackReader. input)
keywordize? eof-error? eof-value)))
(defn read-json
"Reads one JSON value from input String or Reader.
If keywordize? is true (default), object keys will be converted to
keywords. If eof-error? is true (default), empty input will throw
an EOFException; if false EOF will return eof-value. "
([input]
(read-json-from input true true nil))
([input keywordize?]
(read-json-from input keywordize? true nil))
([input keywordize? eof-error? eof-value]
(read-json-from input keywordize? eof-error? eof-value)))
;;; JSON PRINTER
(defprotocol Write-JSON
(write-json [object out]
"Print object to PrintWriter out as JSON"))
(defn- write-json-string [^CharSequence s ^PrintWriter out]
(let [sb (StringBuilder. ^Integer (count s))]
(.append sb \")
(dotimes [i (count s)]
(let [cp (Character/codePointAt s i)]
(cond
;; Handle printable JSON escapes before ASCII
(= cp 34) (.append sb "\\\"")
(= cp 92) (.append sb "\\\\")
(= cp 47) (.append sb "\\/")
;; Print simple ASCII characters
(< 31 cp 127) (.append sb (.charAt s i))
;; Handle non-printable JSON escapes
(= cp 8) (.append sb "\\b")
(= cp 12) (.append sb "\\f")
(= cp 10) (.append sb "\\n")
(= cp 13) (.append sb "\\r")
(= cp 9) (.append sb "\\t")
;; Any other character is Hexadecimal-escaped
:else (.append sb (format "\\u%04x" cp)))))
(.append sb \")
(.print out (str sb))))
(defn- write-json-object [m ^PrintWriter out]
(.print out \{)
(loop [x m]
(when (seq m)
(let [[k v] (first x)]
(when (nil? k)
(throw (Exception. "JSON object keys cannot be nil/null")))
(.print out \")
(.print out (as-str k))
(.print out \")
(.print out \:)
(write-json v out))
(let [nxt (next x)]
(when (seq nxt)
(.print out \,)
(recur nxt)))))
(.print out \}))
(defn- write-json-array [s ^PrintWriter out]
(.print out \[)
(loop [x s]
(when (seq x)
(let [fst (first x)
nxt (next x)]
(write-json fst out)
(when (seq nxt)
(.print out \,)
(recur nxt)))))
(.print out \]))
(defn- write-json-bignum [x ^PrintWriter out]
(.print out (str x)))
(defn- write-json-plain [x ^PrintWriter out]
(.print out x))
(defn- write-json-null [x ^PrintWriter out]
(.print out "null"))
(defn- write-json-named [x ^PrintWriter out]
(write-json-string (name x) out))
(defn- write-json-generic [x out]
(if (.isArray (class x))
(write-json (seq x) out)
(throw (Exception. (str "Don't know how to write JSON of " (class x))))))
(extend nil Write-JSON
{:write-json write-json-null})
(extend clojure.lang.Named Write-JSON
{:write-json write-json-named})
(extend java.lang.Boolean Write-JSON
{:write-json write-json-plain})
(extend java.lang.Number Write-JSON
{:write-json write-json-plain})
(extend java.math.BigInteger Write-JSON
{:write-json write-json-bignum})
(extend java.math.BigDecimal Write-JSON
{:write-json write-json-bignum})
(extend java.lang.CharSequence Write-JSON
{:write-json write-json-string})
(extend java.util.Map Write-JSON
{:write-json write-json-object})
(extend java.util.Collection Write-JSON
{:write-json write-json-array})
(extend clojure.lang.ISeq Write-JSON
{:write-json write-json-array})
(extend java.lang.Object Write-JSON
{:write-json write-json-generic})
(defn json-str
"Converts x to a JSON-formatted string."
[x]
(let [sw (StringWriter.)
out (PrintWriter. sw)]
(write-json x out)
(.toString sw)))
(defn print-json
"Write JSON-formatted output to *out*"
[x]
(write-json x *out*))
;;; JSON PRETTY-PRINTER
;; Based on code by Tom Faulhaber
(defn- pprint-json-array [s]
((formatter-out "~<[~;~@{~w~^, ~:_~}~;]~:>") s))
(defn- pprint-json-object [m]
((formatter-out "~<{~;~@{~<~w:~_~w~:>~^, ~_~}~;}~:>")
(for [[k v] m] [(as-str k) v])))
(defn- pprint-json-generic [x]
(if (.isArray (class x))
(pprint-json-array (seq x))
(print (json-str x))))
(defn- pprint-json-dispatch [x]
(cond (nil? x) (print "null")
(instance? java.util.Map x) (pprint-json-object x)
(instance? java.util.Collection x) (pprint-json-array x)
(instance? clojure.lang.ISeq x) (pprint-json-array x)
:else (pprint-json-generic x)))
(defn pprint-json
"Pretty-prints JSON representation of x to *out*"
[x]
(write x :dispatch pprint-json-dispatch))
Jump to Line
Something went wrong with that request. Please try again.