1 | package org.json; |
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2 | |
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3 | import java.io.IOException; |
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4 | import java.io.Writer; |
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5 | |
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6 | /* |
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7 | Copyright (c) 2006 JSON.org |
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8 | |
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9 | Permission is hereby granted, free of charge, to any person obtaining a copy |
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10 | of this software and associated documentation files (the "Software"), to deal |
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11 | in the Software without restriction, including without limitation the rights |
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12 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
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13 | copies of the Software, and to permit persons to whom the Software is |
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14 | furnished to do so, subject to the following conditions: |
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15 | |
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16 | The above copyright notice and this permission notice shall be included in all |
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17 | copies or substantial portions of the Software. |
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18 | |
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19 | The Software shall be used for Good, not Evil. |
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20 | |
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21 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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22 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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23 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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24 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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25 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
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26 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
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27 | SOFTWARE. |
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28 | */ |
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29 | |
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30 | /** |
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31 | * JSONWriter provides a quick and convenient way of producing JSON text. |
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32 | * The texts produced strictly conform to JSON syntax rules. No whitespace is |
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33 | * added, so the results are ready for transmission or storage. Each instance of |
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34 | * JSONWriter can produce one JSON text. |
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35 | * <p> |
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36 | * A JSONWriter instance provides a <code>value</code> method for appending |
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37 | * values to the |
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38 | * text, and a <code>key</code> |
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39 | * method for adding keys before values in objects. There are <code>array</code> |
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40 | * and <code>endArray</code> methods that make and bound array values, and |
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41 | * <code>object</code> and <code>endObject</code> methods which make and bound |
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42 | * object values. All of these methods return the JSONWriter instance, |
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43 | * permitting a cascade style. For example, <pre> |
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44 | * new JSONWriter(myWriter) |
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45 | * .object() |
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46 | * .key("JSON") |
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47 | * .value("Hello, World!") |
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48 | * .endObject();</pre> which writes <pre> |
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49 | * {"JSON":"Hello, World!"}</pre> |
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50 | * <p> |
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51 | * The first method called must be <code>array</code> or <code>object</code>. |
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52 | * There are no methods for adding commas or colons. JSONWriter adds them for |
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53 | * you. Objects and arrays can be nested up to 20 levels deep. |
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54 | * <p> |
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55 | * This can sometimes be easier than using a JSONObject to build a string. |
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56 | * @author JSON.org |
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57 | * @version 2008-09-18 |
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58 | */ |
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59 | public class JSONWriter { |
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60 | private static final int maxdepth = 20; |
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61 | |
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62 | /** |
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63 | * The comma flag determines if a comma should be output before the next |
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64 | * value. |
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65 | */ |
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66 | private boolean comma; |
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67 | |
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68 | /** |
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69 | * The current mode. Values: |
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70 | * 'a' (array), |
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71 | * 'd' (done), |
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72 | * 'i' (initial), |
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73 | * 'k' (key), |
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74 | * 'o' (object). |
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75 | */ |
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76 | protected char mode; |
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77 | |
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78 | /** |
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79 | * The object/array stack. |
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80 | */ |
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81 | private JSONObject stack[]; |
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82 | |
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83 | /** |
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84 | * The stack top index. A value of 0 indicates that the stack is empty. |
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85 | */ |
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86 | private int top; |
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87 | |
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88 | /** |
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89 | * The writer that will receive the output. |
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90 | */ |
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91 | protected Writer writer; |
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92 | |
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93 | /** |
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94 | * Make a fresh JSONWriter. It can be used to build one JSON text. |
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95 | */ |
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96 | public JSONWriter(Writer w) { |
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97 | this.comma = false; |
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98 | this.mode = 'i'; |
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99 | this.stack = new JSONObject[maxdepth]; |
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100 | this.top = 0; |
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101 | this.writer = w; |
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102 | } |
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103 | |
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104 | /** |
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105 | * Append a value. |
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106 | * @param s A string value. |
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107 | * @return this |
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108 | * @throws JSONException If the value is out of sequence. |
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109 | */ |
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110 | private JSONWriter append(String s) throws JSONException { |
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111 | if (s == null) { |
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112 | throw new JSONException("Null pointer"); |
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113 | } |
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114 | if (this.mode == 'o' || this.mode == 'a') { |
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115 | try { |
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116 | if (this.comma && this.mode == 'a') { |
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117 | this.writer.write(','); |
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118 | } |
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119 | this.writer.write(s); |
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120 | } catch (IOException e) { |
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121 | throw new JSONException(e); |
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122 | } |
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123 | if (this.mode == 'o') { |
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124 | this.mode = 'k'; |
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125 | } |
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126 | this.comma = true; |
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127 | return this; |
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128 | } |
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129 | throw new JSONException("Value out of sequence."); |
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130 | } |
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131 | |
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132 | /** |
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133 | * Begin appending a new array. All values until the balancing |
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134 | * <code>endArray</code> will be appended to this array. The |
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135 | * <code>endArray</code> method must be called to mark the array's end. |
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136 | * @return this |
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137 | * @throws JSONException If the nesting is too deep, or if the object is |
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138 | * started in the wrong place (for example as a key or after the end of the |
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139 | * outermost array or object). |
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140 | */ |
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141 | public JSONWriter array() throws JSONException { |
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142 | if (this.mode == 'i' || this.mode == 'o' || this.mode == 'a') { |
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143 | this.push(null); |
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144 | this.append("["); |
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145 | this.comma = false; |
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146 | return this; |
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147 | } |
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148 | throw new JSONException("Misplaced array."); |
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149 | } |
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150 | |
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151 | /** |
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152 | * End something. |
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153 | * @param m Mode |
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154 | * @param c Closing character |
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155 | * @return this |
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156 | * @throws JSONException If unbalanced. |
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157 | */ |
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158 | private JSONWriter end(char m, char c) throws JSONException { |
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159 | if (this.mode != m) { |
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160 | throw new JSONException(m == 'o' ? "Misplaced endObject." : |
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161 | "Misplaced endArray."); |
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162 | } |
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163 | this.pop(m); |
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164 | try { |
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165 | this.writer.write(c); |
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166 | } catch (IOException e) { |
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167 | throw new JSONException(e); |
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168 | } |
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169 | this.comma = true; |
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170 | return this; |
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171 | } |
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172 | |
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173 | /** |
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174 | * End an array. This method most be called to balance calls to |
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175 | * <code>array</code>. |
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176 | * @return this |
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177 | * @throws JSONException If incorrectly nested. |
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178 | */ |
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179 | public JSONWriter endArray() throws JSONException { |
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180 | return this.end('a', ']'); |
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181 | } |
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182 | |
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183 | /** |
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184 | * End an object. This method most be called to balance calls to |
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185 | * <code>object</code>. |
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186 | * @return this |
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187 | * @throws JSONException If incorrectly nested. |
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188 | */ |
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189 | public JSONWriter endObject() throws JSONException { |
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190 | return this.end('k', '}'); |
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191 | } |
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192 | |
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193 | /** |
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194 | * Append a key. The key will be associated with the next value. In an |
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195 | * object, every value must be preceded by a key. |
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196 | * @param s A key string. |
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197 | * @return this |
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198 | * @throws JSONException If the key is out of place. For example, keys |
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199 | * do not belong in arrays or if the key is null. |
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200 | */ |
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201 | public JSONWriter key(String s) throws JSONException { |
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202 | if (s == null) { |
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203 | throw new JSONException("Null key."); |
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204 | } |
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205 | if (this.mode == 'k') { |
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206 | try { |
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207 | if (this.comma) { |
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208 | this.writer.write(','); |
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209 | } |
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210 | stack[top - 1].putOnce(s, Boolean.TRUE); |
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211 | this.writer.write(JSONObject.quote(s)); |
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212 | this.writer.write(':'); |
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213 | this.comma = false; |
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214 | this.mode = 'o'; |
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215 | return this; |
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216 | } catch (IOException e) { |
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217 | throw new JSONException(e); |
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218 | } |
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219 | } |
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220 | throw new JSONException("Misplaced key."); |
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221 | } |
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222 | |
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223 | |
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224 | /** |
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225 | * Begin appending a new object. All keys and values until the balancing |
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226 | * <code>endObject</code> will be appended to this object. The |
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227 | * <code>endObject</code> method must be called to mark the object's end. |
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228 | * @return this |
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229 | * @throws JSONException If the nesting is too deep, or if the object is |
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230 | * started in the wrong place (for example as a key or after the end of the |
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231 | * outermost array or object). |
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232 | */ |
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233 | public JSONWriter object() throws JSONException { |
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234 | if (this.mode == 'i') { |
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235 | this.mode = 'o'; |
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236 | } |
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237 | if (this.mode == 'o' || this.mode == 'a') { |
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238 | this.append("{"); |
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239 | this.push(new JSONObject()); |
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240 | this.comma = false; |
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241 | return this; |
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242 | } |
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243 | throw new JSONException("Misplaced object."); |
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244 | |
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245 | } |
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246 | |
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247 | |
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248 | /** |
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249 | * Pop an array or object scope. |
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250 | * @param c The scope to close. |
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251 | * @throws JSONException If nesting is wrong. |
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252 | */ |
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253 | private void pop(char c) throws JSONException { |
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254 | if (this.top <= 0) { |
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255 | throw new JSONException("Nesting error."); |
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256 | } |
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257 | char m = this.stack[this.top - 1] == null ? 'a' : 'k'; |
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258 | if (m != c) { |
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259 | throw new JSONException("Nesting error."); |
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260 | } |
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261 | this.top -= 1; |
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262 | this.mode = this.top == 0 ? 'd' : this.stack[this.top - 1] == null ? 'a' : 'k'; |
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263 | } |
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264 | |
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265 | /** |
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266 | * Push an array or object scope. |
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267 | * @param c The scope to open. |
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268 | * @throws JSONException If nesting is too deep. |
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269 | */ |
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270 | private void push(JSONObject jo) throws JSONException { |
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271 | if (this.top >= maxdepth) { |
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272 | throw new JSONException("Nesting too deep."); |
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273 | } |
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274 | this.stack[this.top] = jo; |
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275 | this.mode = jo == null ? 'a' : 'k'; |
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276 | this.top += 1; |
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277 | } |
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278 | |
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279 | |
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280 | /** |
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281 | * Append either the value <code>true</code> or the value |
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282 | * <code>false</code>. |
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283 | * @param b A boolean. |
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284 | * @return this |
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285 | * @throws JSONException |
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286 | */ |
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287 | public JSONWriter value(boolean b) throws JSONException { |
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288 | return this.append(b ? "true" : "false"); |
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289 | } |
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290 | |
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291 | /** |
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292 | * Append a double value. |
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293 | * @param d A double. |
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294 | * @return this |
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295 | * @throws JSONException If the number is not finite. |
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296 | */ |
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297 | public JSONWriter value(double d) throws JSONException { |
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298 | return this.value(new Double(d)); |
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299 | } |
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300 | |
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301 | /** |
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302 | * Append a long value. |
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303 | * @param l A long. |
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304 | * @return this |
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305 | * @throws JSONException |
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306 | */ |
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307 | public JSONWriter value(long l) throws JSONException { |
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308 | return this.append(Long.toString(l)); |
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309 | } |
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310 | |
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311 | |
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312 | /** |
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313 | * Append an object value. |
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314 | * @param o The object to append. It can be null, or a Boolean, Number, |
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315 | * String, JSONObject, or JSONArray, or an object with a toJSONString() |
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316 | * method. |
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317 | * @return this |
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318 | * @throws JSONException If the value is out of sequence. |
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319 | */ |
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320 | public JSONWriter value(Object o) throws JSONException { |
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321 | return this.append(JSONObject.valueToString(o)); |
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322 | } |
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323 | } |
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