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1 | /* |
2 | * Copyright (C) 2008 Google Inc. | |
3 | * | |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); | |
5 | * you may not use this file except in compliance with the License. | |
6 | * You may obtain a copy of the License at | |
7 | * | |
8 | * http://www.apache.org/licenses/LICENSE-2.0 | |
9 | * | |
10 | * Unless required by applicable law or agreed to in writing, software | |
11 | * distributed under the License is distributed on an "AS IS" BASIS, | |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 | * See the License for the specific language governing permissions and | |
14 | * limitations under the License. | |
15 | */ | |
16 | ||
17 | package com.google.gson; | |
18 | ||
19 | import com.google.gson.internal.Streams; | |
20 | import com.google.gson.stream.JsonWriter; | |
21 | import java.io.IOException; | |
22 | import java.io.StringWriter; | |
23 | import java.math.BigDecimal; | |
24 | import java.math.BigInteger; | |
25 | ||
26 | /** | |
27 | * A class representing an element of Json. It could either be a {@link JsonObject}, a | |
28 | * {@link JsonArray}, a {@link JsonPrimitive} or a {@link JsonNull}. | |
29 | * | |
30 | * @author Inderjeet Singh | |
31 | * @author Joel Leitch | |
32 | */ | |
33 | public abstract class JsonElement { | |
34 | /** | |
35 | * Returns a deep copy of this element. Immutable elements like primitives | |
36 | * and nulls are not copied. | |
37 | */ | |
38 | abstract JsonElement deepCopy(); | |
39 | ||
40 | /** | |
41 | * provides check for verifying if this element is an array or not. | |
42 | * | |
43 | * @return true if this element is of type {@link JsonArray}, false otherwise. | |
44 | */ | |
45 | public boolean isJsonArray() { | |
46 | return this instanceof JsonArray; | |
47 | } | |
48 | ||
49 | /** | |
50 | * provides check for verifying if this element is a Json object or not. | |
51 | * | |
52 | * @return true if this element is of type {@link JsonObject}, false otherwise. | |
53 | */ | |
54 | public boolean isJsonObject() { | |
55 | return this instanceof JsonObject; | |
56 | } | |
57 | ||
58 | /** | |
59 | * provides check for verifying if this element is a primitive or not. | |
60 | * | |
61 | * @return true if this element is of type {@link JsonPrimitive}, false otherwise. | |
62 | */ | |
63 | public boolean isJsonPrimitive() { | |
64 | return this instanceof JsonPrimitive; | |
65 | } | |
66 | ||
67 | /** | |
68 | * provides check for verifying if this element represents a null value or not. | |
69 | * | |
70 | * @return true if this element is of type {@link JsonNull}, false otherwise. | |
71 | * @since 1.2 | |
72 | */ | |
73 | public boolean isJsonNull() { | |
74 | return this instanceof JsonNull; | |
75 | } | |
76 | ||
77 | /** | |
78 | * convenience method to get this element as a {@link JsonObject}. If the element is of some | |
79 | * other type, a {@link ClassCastException} will result. Hence it is best to use this method | |
80 | * after ensuring that this element is of the desired type by calling {@link #isJsonObject()} | |
81 | * first. | |
82 | * | |
83 | * @return get this element as a {@link JsonObject}. | |
84 | * @throws IllegalStateException if the element is of another type. | |
85 | */ | |
86 | public JsonObject getAsJsonObject() { | |
87 | if (isJsonObject()) { | |
88 | return (JsonObject) this; | |
89 | } | |
90 | throw new IllegalStateException("Not a JSON Object: " + this); | |
91 | } | |
92 | ||
93 | /** | |
94 | * convenience method to get this element as a {@link JsonArray}. If the element is of some | |
95 | * other type, a {@link ClassCastException} will result. Hence it is best to use this method | |
96 | * after ensuring that this element is of the desired type by calling {@link #isJsonArray()} | |
97 | * first. | |
98 | * | |
99 | * @return get this element as a {@link JsonArray}. | |
100 | * @throws IllegalStateException if the element is of another type. | |
101 | */ | |
102 | public JsonArray getAsJsonArray() { | |
103 | if (isJsonArray()) { | |
104 | return (JsonArray) this; | |
105 | } | |
106 | throw new IllegalStateException("This is not a JSON Array."); | |
107 | } | |
108 | ||
109 | /** | |
110 | * convenience method to get this element as a {@link JsonPrimitive}. If the element is of some | |
111 | * other type, a {@link ClassCastException} will result. Hence it is best to use this method | |
112 | * after ensuring that this element is of the desired type by calling {@link #isJsonPrimitive()} | |
113 | * first. | |
114 | * | |
115 | * @return get this element as a {@link JsonPrimitive}. | |
116 | * @throws IllegalStateException if the element is of another type. | |
117 | */ | |
118 | public JsonPrimitive getAsJsonPrimitive() { | |
119 | if (isJsonPrimitive()) { | |
120 | return (JsonPrimitive) this; | |
121 | } | |
122 | throw new IllegalStateException("This is not a JSON Primitive."); | |
123 | } | |
124 | ||
125 | /** | |
126 | * convenience method to get this element as a {@link JsonNull}. If the element is of some | |
127 | * other type, a {@link ClassCastException} will result. Hence it is best to use this method | |
128 | * after ensuring that this element is of the desired type by calling {@link #isJsonNull()} | |
129 | * first. | |
130 | * | |
131 | * @return get this element as a {@link JsonNull}. | |
132 | * @throws IllegalStateException if the element is of another type. | |
133 | * @since 1.2 | |
134 | */ | |
135 | public JsonNull getAsJsonNull() { | |
136 | if (isJsonNull()) { | |
137 | return (JsonNull) this; | |
138 | } | |
139 | throw new IllegalStateException("This is not a JSON Null."); | |
140 | } | |
141 | ||
142 | /** | |
143 | * convenience method to get this element as a boolean value. | |
144 | * | |
145 | * @return get this element as a primitive boolean value. | |
146 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
147 | * boolean value. | |
148 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
149 | * more than a single element. | |
150 | */ | |
151 | public boolean getAsBoolean() { | |
152 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
153 | } | |
154 | ||
155 | /** | |
156 | * convenience method to get this element as a {@link Boolean} value. | |
157 | * | |
158 | * @return get this element as a {@link Boolean} value. | |
159 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
160 | * boolean value. | |
161 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
162 | * more than a single element. | |
163 | */ | |
164 | Boolean getAsBooleanWrapper() { | |
165 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
166 | } | |
167 | ||
168 | /** | |
169 | * convenience method to get this element as a {@link Number}. | |
170 | * | |
171 | * @return get this element as a {@link Number}. | |
172 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
173 | * number. | |
174 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
175 | * more than a single element. | |
176 | */ | |
177 | public Number getAsNumber() { | |
178 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
179 | } | |
180 | ||
181 | /** | |
182 | * convenience method to get this element as a string value. | |
183 | * | |
184 | * @return get this element as a string value. | |
185 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
186 | * string value. | |
187 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
188 | * more than a single element. | |
189 | */ | |
190 | public String getAsString() { | |
191 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
192 | } | |
193 | ||
194 | /** | |
195 | * convenience method to get this element as a primitive double value. | |
196 | * | |
197 | * @return get this element as a primitive double value. | |
198 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
199 | * double value. | |
200 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
201 | * more than a single element. | |
202 | */ | |
203 | public double getAsDouble() { | |
204 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
205 | } | |
206 | ||
207 | /** | |
208 | * convenience method to get this element as a primitive float value. | |
209 | * | |
210 | * @return get this element as a primitive float value. | |
211 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
212 | * float value. | |
213 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
214 | * more than a single element. | |
215 | */ | |
216 | public float getAsFloat() { | |
217 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
218 | } | |
219 | ||
220 | /** | |
221 | * convenience method to get this element as a primitive long value. | |
222 | * | |
223 | * @return get this element as a primitive long value. | |
224 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
225 | * long value. | |
226 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
227 | * more than a single element. | |
228 | */ | |
229 | public long getAsLong() { | |
230 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
231 | } | |
232 | ||
233 | /** | |
234 | * convenience method to get this element as a primitive integer value. | |
235 | * | |
236 | * @return get this element as a primitive integer value. | |
237 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
238 | * integer value. | |
239 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
240 | * more than a single element. | |
241 | */ | |
242 | public int getAsInt() { | |
243 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
244 | } | |
245 | ||
246 | /** | |
247 | * convenience method to get this element as a primitive byte value. | |
248 | * | |
249 | * @return get this element as a primitive byte value. | |
250 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
251 | * byte value. | |
252 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
253 | * more than a single element. | |
254 | * @since 1.3 | |
255 | */ | |
256 | public byte getAsByte() { | |
257 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
258 | } | |
259 | ||
260 | /** | |
261 | * convenience method to get this element as a primitive character value. | |
262 | * | |
263 | * @return get this element as a primitive char value. | |
264 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
265 | * char value. | |
266 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
267 | * more than a single element. | |
268 | * @since 1.3 | |
269 | */ | |
270 | public char getAsCharacter() { | |
271 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
272 | } | |
273 | ||
274 | /** | |
275 | * convenience method to get this element as a {@link BigDecimal}. | |
276 | * | |
277 | * @return get this element as a {@link BigDecimal}. | |
278 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive}. | |
279 | * * @throws NumberFormatException if the element is not a valid {@link BigDecimal}. | |
280 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
281 | * more than a single element. | |
282 | * @since 1.2 | |
283 | */ | |
284 | public BigDecimal getAsBigDecimal() { | |
285 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
286 | } | |
287 | ||
288 | /** | |
289 | * convenience method to get this element as a {@link BigInteger}. | |
290 | * | |
291 | * @return get this element as a {@link BigInteger}. | |
292 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive}. | |
293 | * @throws NumberFormatException if the element is not a valid {@link BigInteger}. | |
294 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
295 | * more than a single element. | |
296 | * @since 1.2 | |
297 | */ | |
298 | public BigInteger getAsBigInteger() { | |
299 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
300 | } | |
301 | ||
302 | /** | |
303 | * convenience method to get this element as a primitive short value. | |
304 | * | |
305 | * @return get this element as a primitive short value. | |
306 | * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid | |
307 | * short value. | |
308 | * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains | |
309 | * more than a single element. | |
310 | */ | |
311 | public short getAsShort() { | |
312 | throw new UnsupportedOperationException(getClass().getSimpleName()); | |
313 | } | |
314 | ||
315 | /** | |
316 | * Returns a String representation of this element. | |
317 | */ | |
318 | @Override | |
319 | public String toString() { | |
320 | try { | |
321 | StringWriter stringWriter = new StringWriter(); | |
322 | JsonWriter jsonWriter = new JsonWriter(stringWriter); | |
323 | jsonWriter.setLenient(true); | |
324 | Streams.write(this, jsonWriter); | |
325 | return stringWriter.toString(); | |
326 | } catch (IOException e) { | |
327 | throw new AssertionError(e); | |
328 | } | |
329 | } | |
330 | } |