source: josm/trunk/src/org/json/JSONWriter.java@ 6711

Last change on this file since 6711 was 6484, checked in by Don-vip, 11 years ago

see #7307, fix #8474 - use org.json as lightweight internal json library (already being used by several plugins)
File size: 10.4 KB
Line 
1package org.json;
2
3import java.io.IOException;
4import java.io.Writer;
5
6/*
7Copyright (c) 2006 JSON.org
8
9Permission is hereby granted, free of charge, to any person obtaining a copy
10of this software and associated documentation files (the "Software"), to deal
11in the Software without restriction, including without limitation the rights
12to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
13copies of the Software, and to permit persons to whom the Software is
14furnished to do so, subject to the following conditions:
15
16The above copyright notice and this permission notice shall be included in all
17copies or substantial portions of the Software.
18
19The Software shall be used for Good, not Evil.
20
21THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
22IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
23FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
24AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
25LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
26OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
27SOFTWARE.
28*/
29
30/**
31 * JSONWriter provides a quick and convenient way of producing JSON text.
32 * The texts produced strictly conform to JSON syntax rules. No whitespace is
33 * added, so the results are ready for transmission or storage. Each instance of
34 * JSONWriter can produce one JSON text.
35 * <p>
36 * A JSONWriter instance provides a <code>value</code> method for appending
37 * values to the
38 * text, and a <code>key</code>
39 * method for adding keys before values in objects. There are <code>array</code>
40 * and <code>endArray</code> methods that make and bound array values, and
41 * <code>object</code> and <code>endObject</code> methods which make and bound
42 * object values. All of these methods return the JSONWriter instance,
43 * permitting a cascade style. For example, <pre>
44 * new JSONWriter(myWriter)
45 * .object()
46 * .key("JSON")
47 * .value("Hello, World!")
48 * .endObject();</pre> which writes <pre>
49 * {"JSON":"Hello, World!"}</pre>
50 * <p>
51 * The first method called must be <code>array</code> or <code>object</code>.
52 * There are no methods for adding commas or colons. JSONWriter adds them for
53 * you. Objects and arrays can be nested up to 20 levels deep.
54 * <p>
55 * This can sometimes be easier than using a JSONObject to build a string.
56 * @author JSON.org
57 * @version 2011-11-24
58 */
59public class JSONWriter {
60 private static final int maxdepth = 200;
61
62 /**
63 * The comma flag determines if a comma should be output before the next
64 * value.
65 */
66 private boolean comma;
67
68 /**
69 * The current mode. Values:
70 * 'a' (array),
71 * 'd' (done),
72 * 'i' (initial),
73 * 'k' (key),
74 * 'o' (object).
75 */
76 protected char mode;
77
78 /**
79 * The object/array stack.
80 */
81 private final JSONObject stack[];
82
83 /**
84 * The stack top index. A value of 0 indicates that the stack is empty.
85 */
86 private int top;
87
88 /**
89 * The writer that will receive the output.
90 */
91 protected Writer writer;
92
93 /**
94 * Make a fresh JSONWriter. It can be used to build one JSON text.
95 */
96 public JSONWriter(Writer w) {
97 this.comma = false;
98 this.mode = 'i';
99 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 c 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}
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