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1 ;;; json.clj: A pretty printing version of the JavaScript Object Notation (JSON) generator
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2
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3 ;; by Tom Faulhaber, based on the version by Stuart Sierra (clojure.contrib.json.write)
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4 ;; May 9, 2009
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5
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6 ;; Copyright (c) Tom Faulhaber/Stuart Sierra, 2009. All rights reserved. The use
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7 ;; and distribution terms for this software are covered by the Eclipse
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8 ;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
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9 ;; which can be found in the file epl-v10.html at the root of this
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10 ;; distribution. By using this software in any fashion, you are
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11 ;; agreeing to be bound by the terms of this license. You must not
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12 ;; remove this notice, or any other, from this software.
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13
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14
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15 (ns
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16 #^{:author "Tom Faulhaber (based on the version by Stuart Sierra)",
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17 :doc "Pretty printing JavaScript Object Notation (JSON) generator.
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18
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19 This is an example of using a pretty printer dispatch function to generate JSON output",
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20 :see-also [["http://json.org/", "JSON Home Page"]]}
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21 clojure.contrib.pprint.examples.json
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22 (:use [clojure.test :only (deftest- is)]
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23 [clojure.contrib.string :only (as-str)]
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24 [clojure.contrib.pprint :only (write formatter-out)]))
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25
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26
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27
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28 (defmulti dispatch-json
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29 "The dispatch function for printing objects as JSON"
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30 {:arglists '[[x]]}
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31 (fn [x] (cond
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32 (nil? x) nil ;; prevent NullPointerException on next line
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33 (.isArray (class x)) ::array
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34 :else (type x))))
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35
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36 ;; Primitive types can be printed with Clojure's pr function.
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37 (derive java.lang.Boolean ::pr)
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38 (derive java.lang.Byte ::pr)
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39 (derive java.lang.Short ::pr)
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40 (derive java.lang.Integer ::pr)
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41 (derive java.lang.Long ::pr)
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42 (derive java.lang.Float ::pr)
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43 (derive java.lang.Double ::pr)
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44
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45 ;; Collection types can be printed as JSON objects or arrays.
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46 (derive java.util.Map ::object)
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47 (derive java.util.Collection ::array)
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48
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49 ;; Symbols and keywords are converted to strings.
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50 (derive clojure.lang.Symbol ::symbol)
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51 (derive clojure.lang.Keyword ::symbol)
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52
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53
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54 (defmethod dispatch-json ::pr [x] (pr x))
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55
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56 (defmethod dispatch-json nil [x] (print "null"))
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57
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58 (defmethod dispatch-json ::symbol [x] (pr (name x)))
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59
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60 (defmethod dispatch-json ::array [s]
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61 ((formatter-out "~<[~;~@{~w~^, ~:_~}~;]~:>") s))
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62
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63 (defmethod dispatch-json ::object [m]
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64 ((formatter-out "~<{~;~@{~<~w:~_~w~:>~^, ~_~}~;}~:>")
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65 (for [[k v] m] [(as-str k) v])))
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66
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67 (defmethod dispatch-json java.lang.CharSequence [s]
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68 (print \")
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69 (dotimes [i (count s)]
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70 (let [cp (Character/codePointAt s i)]
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71 (cond
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72 ;; Handle printable JSON escapes before ASCII
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73 (= cp 34) (print "\\\"")
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74 (= cp 92) (print "\\\\")
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75 ;; Print simple ASCII characters
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76 (< 31 cp 127) (print (.charAt s i))
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77 ;; Handle non-printable JSON escapes
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78 (= cp 8) (print "\\b")
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79 (= cp 12) (print "\\f")
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80 (= cp 10) (print "\\n")
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81 (= cp 13) (print "\\r")
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82 (= cp 9) (print "\\t")
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83 ;; Any other character is printed as Hexadecimal escape
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84 :else (printf "\\u%04x" cp))))
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85 (print \"))
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86
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87 (defn print-json
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88 "Prints x as JSON. Nil becomes JSON null. Keywords become
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89 strings, without the leading colon. Maps become JSON objects, all
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90 other collection types become JSON arrays. Java arrays become JSON
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91 arrays. Unicode characters in strings are escaped as \\uXXXX.
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92 Numbers print as with pr."
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93 [x]
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94 (write x :dispatch dispatch-json))
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95
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96 (defn json-str
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97 "Converts x to a JSON-formatted string."
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98 [x]
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99 (with-out-str (print-json x)))
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100
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101
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102
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103 ;;; TESTS
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104
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105 ;; Run these tests with
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106 ;; (clojure.test/run-tests 'clojure.contrib.print-json)
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107
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108 ;; Bind clojure.test/*load-tests* to false to omit these
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109 ;; tests from production code.
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110
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111 (deftest- can-print-json-strings
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112 (is (= "\"Hello, World!\"" (json-str "Hello, World!")))
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113 (is (= "\"\\\"Embedded\\\" Quotes\"" (json-str "\"Embedded\" Quotes"))))
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114
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115 (deftest- can-print-unicode
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116 (is (= "\"\\u1234\\u4567\"" (json-str "\u1234\u4567"))))
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117
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118 (deftest- can-print-json-null
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119 (is (= "null" (json-str nil))))
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120
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121 (deftest- can-print-json-arrays
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122 (is (= "[1, 2, 3]" (json-str [1 2 3])))
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123 (is (= "[1, 2, 3]" (json-str (list 1 2 3))))
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124 (is (= "[1, 2, 3]" (json-str (sorted-set 1 2 3))))
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125 (is (= "[1, 2, 3]" (json-str (seq [1 2 3])))))
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126
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127 (deftest- can-print-java-arrays
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128 (is (= "[1, 2, 3]" (json-str (into-array [1 2 3])))))
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129
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130 (deftest- can-print-empty-arrays
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131 (is (= "[]" (json-str [])))
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132 (is (= "[]" (json-str (list))))
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133 (is (= "[]" (json-str #{}))))
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134
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135 (deftest- can-print-json-objects
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136 (is (= "{\"a\":1, \"b\":2}" (json-str (sorted-map :a 1 :b 2)))))
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137
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138 (deftest- object-keys-must-be-strings
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139 (is (= "{\"1\":1, \"2\":2}" (json-str (sorted-map 1 1 2 2)))))
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140
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141 (deftest- can-print-empty-objects
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142 (is (= "{}" (json-str {}))))
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