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/src/org/json/JSONWriter.java

http://github.com/nddrylliog/ooc
Java | 323 lines | 132 code | 27 blank | 164 comment | 39 complexity | 4d91d723b1ce59a77ee508cc0f85edcd MD5 | raw file
  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 2008-09-22
 58 */
 59public class JSONWriter {
 60    private static final int maxdepth = 20;
 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 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 s A string value.
107     * @return this
108     * @throws JSONException If the value is out of sequence.
109     */
110    private JSONWriter append(String s) throws JSONException {
111        if (s == 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(s);
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 m Mode
154     * @param c Closing character
155     * @return this
156     * @throws JSONException If unbalanced.
157     */
158    private JSONWriter end(char m, char c) throws JSONException {
159        if (this.mode != m) {
160            throw new JSONException(m == 'o' ? "Misplaced endObject." :
161                "Misplaced endArray.");
162        }
163        this.pop(m);
164        try {
165            this.writer.write(c);
166        } catch (IOException e) {
167            throw new JSONException(e);
168        }
169        this.comma = true;
170        return this;
171    }
172
173    /**
174     * End an array. This method most be called to balance calls to
175     * <code>array</code>.
176     * @return this
177     * @throws JSONException If incorrectly nested.
178     */
179    public JSONWriter endArray() throws JSONException {
180        return this.end('a', ']');
181    }
182
183    /**
184     * End an object. This method most be called to balance calls to
185     * <code>object</code>.
186     * @return this
187     * @throws JSONException If incorrectly nested.
188     */
189    public JSONWriter endObject() throws JSONException {
190        return this.end('k', '}');
191    }
192
193    /**
194     * Append a key. The key will be associated with the next value. In an
195     * object, every value must be preceded by a key.
196     * @param s A key string.
197     * @return this
198     * @throws JSONException If the key is out of place. For example, keys
199     *  do not belong in arrays or if the key is null.
200     */
201    public JSONWriter key(String s) throws JSONException {
202        if (s == null) {
203            throw new JSONException("Null key.");
204        }
205        if (this.mode == 'k') {
206            try {
207                stack[top - 1].putOnce(s, Boolean.TRUE);
208                if (this.comma) {
209                    this.writer.write(',');
210                }
211                this.writer.write(JSONObject.quote(s));
212                this.writer.write(':');
213                this.comma = false;
214                this.mode = 'o';
215                return this;
216            } catch (IOException e) {
217                throw new JSONException(e);
218            }
219        }
220        throw new JSONException("Misplaced key.");
221    }
222
223
224    /**
225     * Begin appending a new object. All keys and values until the balancing
226     * <code>endObject</code> will be appended to this object. The
227     * <code>endObject</code> method must be called to mark the object's end.
228     * @return this
229     * @throws JSONException If the nesting is too deep, or if the object is
230     * started in the wrong place (for example as a key or after the end of the
231     * outermost array or object).
232     */
233    public JSONWriter object() throws JSONException {
234        if (this.mode == 'i') {
235            this.mode = 'o';
236        }
237        if (this.mode == 'o' || this.mode == 'a') {
238            this.append("{");
239            this.push(new JSONObject());
240            this.comma = false;
241            return this;
242        }
243        throw new JSONException("Misplaced object.");
244
245    }
246
247
248    /**
249     * Pop an array or object scope.
250     * @param c The scope to close.
251     * @throws JSONException If nesting is wrong.
252     */
253    private void pop(char c) throws JSONException {
254        if (this.top <= 0) {
255            throw new JSONException("Nesting error.");
256        }
257        char m = this.stack[this.top - 1] == null ? 'a' : 'k';
258        if (m != c) {
259            throw new JSONException("Nesting error.");
260        }
261        this.top -= 1;
262        this.mode = this.top == 0 ? 'd' : this.stack[this.top - 1] == null ? 'a' : 'k';
263    }
264
265    /**
266     * Push an array or object scope.
267     * @param c The scope to open.
268     * @throws JSONException If nesting is too deep.
269     */
270    private void push(JSONObject jo) throws JSONException {
271        if (this.top >= maxdepth) {
272            throw new JSONException("Nesting too deep.");
273        }
274        this.stack[this.top] = jo;
275        this.mode = jo == null ? 'a' : 'k';
276        this.top += 1;
277    }
278
279
280    /**
281     * Append either the value <code>true</code> or the value
282     * <code>false</code>.
283     * @param b A boolean.
284     * @return this
285     * @throws JSONException
286     */
287    public JSONWriter value(boolean b) throws JSONException {
288        return this.append(b ? "true" : "false");
289    }
290
291    /**
292     * Append a double value.
293     * @param d A double.
294     * @return this
295     * @throws JSONException If the number is not finite.
296     */
297    public JSONWriter value(double d) throws JSONException {
298        return this.value(new Double(d));
299    }
300
301    /**
302     * Append a long value.
303     * @param l A long.
304     * @return this
305     * @throws JSONException
306     */
307    public JSONWriter value(long l) throws JSONException {
308        return this.append(Long.toString(l));
309    }
310
311
312    /**
313     * Append an object value.
314     * @param o The object to append. It can be null, or a Boolean, Number,
315     *   String, JSONObject, or JSONArray, or an object with a toJSONString()
316     *   method.
317     * @return this
318     * @throws JSONException If the value is out of sequence.
319     */
320    public JSONWriter value(Object o) throws JSONException {
321        return this.append(JSONObject.valueToString(o));
322    }
323}