001package org.json; 002 003import java.io.IOException; 004import java.io.Writer; 005 006/* 007Copyright (c) 2006 JSON.org 008 009Permission is hereby granted, free of charge, to any person obtaining a copy 010of this software and associated documentation files (the "Software"), to deal 011in the Software without restriction, including without limitation the rights 012to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 013copies of the Software, and to permit persons to whom the Software is 014furnished to do so, subject to the following conditions: 015 016The above copyright notice and this permission notice shall be included in all 017copies or substantial portions of the Software. 018 019The Software shall be used for Good, not Evil. 020 021THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 022IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 023FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 024AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 025LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 026OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 027SOFTWARE. 028*/ 029 030/** 031 * JSONWriter provides a quick and convenient way of producing JSON text. 032 * The texts produced strictly conform to JSON syntax rules. No whitespace is 033 * added, so the results are ready for transmission or storage. Each instance of 034 * JSONWriter can produce one JSON text. 035 * <p> 036 * A JSONWriter instance provides a <code>value</code> method for appending 037 * values to the 038 * text, and a <code>key</code> 039 * method for adding keys before values in objects. There are <code>array</code> 040 * and <code>endArray</code> methods that make and bound array values, and 041 * <code>object</code> and <code>endObject</code> methods which make and bound 042 * object values. All of these methods return the JSONWriter instance, 043 * permitting a cascade style. For example, <pre> 044 * new JSONWriter(myWriter) 045 * .object() 046 * .key("JSON") 047 * .value("Hello, World!") 048 * .endObject();</pre> which writes <pre> 049 * {"JSON":"Hello, World!"}</pre> 050 * <p> 051 * The first method called must be <code>array</code> or <code>object</code>. 052 * There are no methods for adding commas or colons. JSONWriter adds them for 053 * you. Objects and arrays can be nested up to 20 levels deep. 054 * <p> 055 * This can sometimes be easier than using a JSONObject to build a string. 056 * @author JSON.org 057 * @version 2015-12-09 058 */ 059public class JSONWriter { 060 private static final int maxdepth = 200; 061 062 /** 063 * The comma flag determines if a comma should be output before the next 064 * value. 065 */ 066 private boolean comma; 067 068 /** 069 * The current mode. Values: 070 * 'a' (array), 071 * 'd' (done), 072 * 'i' (initial), 073 * 'k' (key), 074 * 'o' (object). 075 */ 076 protected char mode; 077 078 /** 079 * The object/array stack. 080 */ 081 private final JSONObject stack[]; 082 083 /** 084 * The stack top index. A value of 0 indicates that the stack is empty. 085 */ 086 private int top; 087 088 /** 089 * The writer that will receive the output. 090 */ 091 protected Writer writer; 092 093 /** 094 * Make a fresh JSONWriter. It can be used to build one JSON text. 095 */ 096 public JSONWriter(Writer w) { 097 this.comma = false; 098 this.mode = 'i'; 099 this.stack = new JSONObject[maxdepth]; 100 this.top = 0; 101 this.writer = w; 102 } 103 104 /** 105 * Append a value. 106 * @param string A string value. 107 * @return this 108 * @throws JSONException If the value is out of sequence. 109 */ 110 private JSONWriter append(String string) throws JSONException { 111 if (string == null) { 112 throw new JSONException("Null pointer"); 113 } 114 if (this.mode == 'o' || this.mode == 'a') { 115 try { 116 if (this.comma && this.mode == 'a') { 117 this.writer.write(','); 118 } 119 this.writer.write(string); 120 } catch (IOException e) { 121 throw new JSONException(e); 122 } 123 if (this.mode == 'o') { 124 this.mode = 'k'; 125 } 126 this.comma = true; 127 return this; 128 } 129 throw new JSONException("Value out of sequence."); 130 } 131 132 /** 133 * Begin appending a new array. All values until the balancing 134 * <code>endArray</code> will be appended to this array. The 135 * <code>endArray</code> method must be called to mark the array's end. 136 * @return this 137 * @throws JSONException If the nesting is too deep, or if the object is 138 * started in the wrong place (for example as a key or after the end of the 139 * outermost array or object). 140 */ 141 public JSONWriter array() throws JSONException { 142 if (this.mode == 'i' || this.mode == 'o' || this.mode == 'a') { 143 this.push(null); 144 this.append("["); 145 this.comma = false; 146 return this; 147 } 148 throw new JSONException("Misplaced array."); 149 } 150 151 /** 152 * End something. 153 * @param mode Mode 154 * @param c Closing character 155 * @return this 156 * @throws JSONException If unbalanced. 157 */ 158 private JSONWriter end(char mode, char c) throws JSONException { 159 if (this.mode != mode) { 160 throw new JSONException(mode == 'a' 161 ? "Misplaced endArray." 162 : "Misplaced endObject."); 163 } 164 this.pop(mode); 165 try { 166 this.writer.write(c); 167 } catch (IOException e) { 168 throw new JSONException(e); 169 } 170 this.comma = true; 171 return this; 172 } 173 174 /** 175 * End an array. This method most be called to balance calls to 176 * <code>array</code>. 177 * @return this 178 * @throws JSONException If incorrectly nested. 179 */ 180 public JSONWriter endArray() throws JSONException { 181 return this.end('a', ']'); 182 } 183 184 /** 185 * End an object. This method most be called to balance calls to 186 * <code>object</code>. 187 * @return this 188 * @throws JSONException If incorrectly nested. 189 */ 190 public JSONWriter endObject() throws JSONException { 191 return this.end('k', '}'); 192 } 193 194 /** 195 * Append a key. The key will be associated with the next value. In an 196 * object, every value must be preceded by a key. 197 * @param string A key string. 198 * @return this 199 * @throws JSONException If the key is out of place. For example, keys 200 * do not belong in arrays or if the key is null. 201 */ 202 public JSONWriter key(String string) throws JSONException { 203 if (string == null) { 204 throw new JSONException("Null key."); 205 } 206 if (this.mode == 'k') { 207 try { 208 this.stack[this.top - 1].putOnce(string, Boolean.TRUE); 209 if (this.comma) { 210 this.writer.write(','); 211 } 212 this.writer.write(JSONObject.quote(string)); 213 this.writer.write(':'); 214 this.comma = false; 215 this.mode = 'o'; 216 return this; 217 } catch (IOException e) { 218 throw new JSONException(e); 219 } 220 } 221 throw new JSONException("Misplaced key."); 222 } 223 224 225 /** 226 * Begin appending a new object. All keys and values until the balancing 227 * <code>endObject</code> will be appended to this object. The 228 * <code>endObject</code> method must be called to mark the object's end. 229 * @return this 230 * @throws JSONException If the nesting is too deep, or if the object is 231 * started in the wrong place (for example as a key or after the end of the 232 * outermost array or object). 233 */ 234 public JSONWriter object() throws JSONException { 235 if (this.mode == 'i') { 236 this.mode = 'o'; 237 } 238 if (this.mode == 'o' || this.mode == 'a') { 239 this.append("{"); 240 this.push(new JSONObject()); 241 this.comma = false; 242 return this; 243 } 244 throw new JSONException("Misplaced object."); 245 246 } 247 248 249 /** 250 * Pop an array or object scope. 251 * @param c The scope to close. 252 * @throws JSONException If nesting is wrong. 253 */ 254 private void pop(char c) throws JSONException { 255 if (this.top <= 0) { 256 throw new JSONException("Nesting error."); 257 } 258 char m = this.stack[this.top - 1] == null ? 'a' : 'k'; 259 if (m != c) { 260 throw new JSONException("Nesting error."); 261 } 262 this.top -= 1; 263 this.mode = this.top == 0 264 ? 'd' 265 : this.stack[this.top - 1] == null 266 ? 'a' 267 : 'k'; 268 } 269 270 /** 271 * Push an array or object scope. 272 * @param jo The scope to open. 273 * @throws JSONException If nesting is too deep. 274 */ 275 private void push(JSONObject jo) throws JSONException { 276 if (this.top >= maxdepth) { 277 throw new JSONException("Nesting too deep."); 278 } 279 this.stack[this.top] = jo; 280 this.mode = jo == null ? 'a' : 'k'; 281 this.top += 1; 282 } 283 284 285 /** 286 * Append either the value <code>true</code> or the value 287 * <code>false</code>. 288 * @param b A boolean. 289 * @return this 290 * @throws JSONException 291 */ 292 public JSONWriter value(boolean b) throws JSONException { 293 return this.append(b ? "true" : "false"); 294 } 295 296 /** 297 * Append a double value. 298 * @param d A double. 299 * @return this 300 * @throws JSONException If the number is not finite. 301 */ 302 public JSONWriter value(double d) throws JSONException { 303 return this.value(new Double(d)); 304 } 305 306 /** 307 * Append a long value. 308 * @param l A long. 309 * @return this 310 * @throws JSONException 311 */ 312 public JSONWriter value(long l) throws JSONException { 313 return this.append(Long.toString(l)); 314 } 315 316 317 /** 318 * Append an object value. 319 * @param object The object to append. It can be null, or a Boolean, Number, 320 * String, JSONObject, or JSONArray, or an object that implements JSONString. 321 * @return this 322 * @throws JSONException If the value is out of sequence. 323 */ 324 public JSONWriter value(Object object) throws JSONException { 325 return this.append(JSONObject.valueToString(object)); 326 } 327}