1 /*
2 * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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24 */
25
26 package javax.xml.xpath;
27
28 import javax.xml.namespace.QName;
29 import org.xml.sax.InputSource;
30
31 /**
32 * {@code XPathExpression} provides access to compiled XPath expressions.
33 *
34 * <a name="XPathExpression-evaluation"></a>
35 * <table border="1" cellpadding="2">
36 * <thead>
37 * <tr>
38 * <th colspan="2">Evaluation of XPath Expressions.</th>
39 * </tr>
40 * </thead>
41 * <tbody>
42 * <tr>
43 * <td>context</td>
44 * <td>
45 * If a request is made to evaluate the expression in the absence
46 * of a context item, an empty document node will be used for the context.
47 * For the purposes of evaluating XPath expressions, a DocumentFragment
48 * is treated like a Document node.
49 * </td>
50 * </tr>
51 * <tr>
52 * <td>variables</td>
53 * <td>
54 * If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}.
55 * An {@link XPathExpressionException} is raised if the variable resolver is undefined or
56 * the resolver returns {@code null} for the variable.
57 * The value of a variable must be immutable through the course of any single evaluation.
58 * </td>
59 * </tr>
60 * <tr>
61 * <td>functions</td>
62 * <td>
63 * If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}.
64 * An {@link XPathExpressionException} is raised if the function resolver is undefined or
65 * the function resolver returns {@code null} for the function.
66 * </td>
67 * </tr>
68 * <tr>
69 * <td>QNames</td>
70 * <td>
71 * QNames in the expression are resolved against the XPath namespace context.
72 * </td>
73 * </tr>
74 * <tr>
75 * <td>result</td>
76 * <td>
77 * This result of evaluating an expression is converted to an instance of the desired return type.
78 * Valid return types are defined in {@link XPathConstants}.
79 * Conversion to the return type follows XPath conversion rules.
80 * </td>
81 * </tr>
82 * </tbody>
83 * </table>
84 *
85 * <p>An XPath expression is not thread-safe and not reentrant.
86 * In other words, it is the application's responsibility to make
87 * sure that one {@link XPathExpression} object is not used from
88 * more than one thread at any given time, and while the {@code evaluate}
89 * method is invoked, applications may not recursively call
90 * the {@code evaluate} method.
91 *
92 * @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
93 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
94 * @see <a href="http://www.w3.org/TR/xpath#section-Expressions">XML Path Language (XPath) Version 1.0, Expressions</a>
95 * @since 1.5
96 */
97 public interface XPathExpression {
98
99
100 /**
101 * Evaluate the compiled XPath expression in the specified context and return the result as the specified type.
102 *
103 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
104 * variable, function and QName resolution and return type conversion.
105 *
106 * <p>
107 * The parameter {@code item} represents the context the XPath expression
108 * will be operated on. The type of the context is implementation-dependent.
109 * If the value is {@code null}, the operation must have no dependency on
110 * the context, otherwise an XPathExpressionException will be thrown.
111 *
112 * @implNote
113 * The type of the context is usually {@link org.w3c.dom.Node}.
114 *
115 * @param item The context the XPath expression will be evaluated in.
116 * @param returnType The result type expected to be returned by the XPath expression.
117 *
118 * @return The {@code Object} that is the result of evaluating the expression and converting the result to
119 * {@code returnType}.
120 *
121 * @throws XPathExpressionException If the expression cannot be evaluated.
122 * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.
123 * @throws NullPointerException If {@code returnType} is {@code null}.
124 */
125 public Object evaluate(Object item, QName returnType)
126 throws XPathExpressionException;
127
128 /**
129 * Evaluate the compiled XPath expression in the specified context and return the result as a {@code String}.
130 *
131 * <p>This method calls {@link #evaluate(Object item, QName returnType)} with a {@code returnType} of
132 * {@link XPathConstants#STRING}.
133 *
134 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
135 * variable, function and QName resolution and return type conversion.
136 *
137 * <p>
138 * The parameter {@code item} represents the context the XPath expression
139 * will be operated on. The type of the context is implementation-dependent.
140 * If the value is {@code null}, the operation must have no dependency on
141 * the context, otherwise an XPathExpressionException will be thrown.
142 *
143 * @implNote
144 * The type of the context is usually {@link org.w3c.dom.Node}.
145 *
146 * @param item The context the XPath expression will be evaluated in.
147 *
148 * @return The result of evaluating an XPath expression as a {@code String}.
149 *
150 * @throws XPathExpressionException If the expression cannot be evaluated.
151 */
152 public String evaluate(Object item)
153 throws XPathExpressionException;
154
155 /**
156 * Evaluate the compiled XPath expression in the context
157 * of the specified {@code InputSource} and return the result as the
158 * specified type.
159 *
160 * <p>This method builds a data model for the {@link InputSource} and calls
161 * {@link #evaluate(Object item, QName returnType)} on the resulting document object.
162 *
163 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
164 * variable, function and QName resolution and return type conversion.
165 *
166 * <p>If {@code returnType} is not one of the types defined in {@link XPathConstants},
167 * then an {@code IllegalArgumentException} is thrown.
168 *
169 * <p>If {@code source} or {@code returnType} is {@code null},
170 * then a {@code NullPointerException} is thrown.
171 *
172 * @param source The {@code InputSource} of the document to evaluate over.
173 * @param returnType The desired return type.
174 *
175 * @return The {@code Object} that is the result of evaluating the expression and converting the result to
176 * {@code returnType}.
177 *
178 * @throws XPathExpressionException If the expression cannot be evaluated.
179 * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.
180 * @throws NullPointerException If {@code source or returnType} is {@code null}.
181 */
182 public Object evaluate(InputSource source, QName returnType)
183 throws XPathExpressionException;
184
185 /**
186 * Evaluate the compiled XPath expression in the context
187 * of the specified {@code InputSource} and return the result as a
188 * {@code String}.
189 *
190 * <p>This method calls {@link #evaluate(InputSource source, QName returnType)} with a {@code returnType} of
191 * {@link XPathConstants#STRING}.
192 *
193 * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
194 * variable, function and QName resolution and return type conversion.
195 *
196 * <p>If {@code source} is {@code null}, then a {@code NullPointerException} is thrown.
197 *
198 * @param source The {@code InputSource} of the document to evaluate over.
199 *
200 * @return The {@code String} that is the result of evaluating the expression and converting the result to a
201 * {@code String}.
202 *
203 * @throws XPathExpressionException If the expression cannot be evaluated.
204 * @throws NullPointerException If {@code source} is {@code null}.
205 */
206 public String evaluate(InputSource source)
207 throws XPathExpressionException;
208
209 /**
210 * Evaluate the compiled XPath expression in the specified context, and return
211 * the result with the type specified through the {@code class type}.
212 *
213 * <p>
214 * The parameter {@code item} represents the context the XPath expression
215 * will be operated on. The type of the context is implementation-dependent.
216 * If the value is {@code null}, the operation must have no dependency on
217 * the context, otherwise an XPathExpressionException will be thrown.
218 *
219 * @implNote
220 * The type of the context is usually {@link org.w3c.dom.Node}.
221 *
222 * @implSpec
223 * The default implementation in the XPath API is equivalent to:
224 * <pre> {@code
225 * (T)evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type));
226 * }</pre>
227 *
228 * Since the {@code evaluate} method does not support the
229 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
230 * XPathEvaluationResult as the type will result in IllegalArgumentException.
231 * Any implementation supporting the
232 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
233 * this method.
234 *
235 * @param <T> The class type that will be returned by the XPath expression.
236 * @param item The context the XPath expression will be evaluated in.
237 * @param type The class type expected to be returned by the XPath expression.
238 *
239 * @return The result of evaluating the expression.
240 *
241 * @throws XPathExpressionException If the expression cannot be evaluated.
242 * @throws IllegalArgumentException If {@code type} is not of the types
243 * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType
244 * XPathResultType}, or XPathEvaluationResult is specified as the type but an
245 * implementation supporting the
246 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type is not available.
247 * @throws NullPointerException If {@code type} is {@code null}.
248 *
249 * @since 1.9
250 */
251 default <T>T evaluateExpression(Object item, Class<T> type)
252 throws XPathExpressionException
253 {
254 return type.cast(evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type)));
255 }
256
257 /**
258 * Evaluate the compiled XPath expression in the specified context. This is
259 * equivalent to calling {@link #evaluateExpression(Object item, Class type)}
260 * with type {@link XPathEvaluationResult}:
261 * <pre> {@code
262 * evaluateExpression(item, XPathEvaluationResult.class);
263 * }</pre>
264 * <p>
265 * The parameter {@code item} represents the context the XPath expression
266 * will be operated on. The type of the context is implementation-dependent.
267 * If the value is {@code null}, the operation must have no dependency on
268 * the context, otherwise an XPathExpressionException will be thrown.
269 *
270 * @implNote
271 * The type of the context is usually {@link org.w3c.dom.Node}.
272 *
273 * @implSpec
274 * The default implementation in the XPath API is equivalent to:
275 * <pre> {@code
276 * evaluateExpression(item, XPathEvaluationResult.class);
277 * }</pre>
278 *
279 * Since the {@code evaluate} method does not support the
280 * {@link XPathEvaluationResult.XPathResultType#ANY ANY}
281 * type, the default implementation of this method will always throw an
282 * IllegalArgumentException. Any implementation supporting the
283 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
284 * override this method.
285 *
286 * @param item The context the XPath expression will be evaluated in.
287 *
288 * @return The result of evaluating the expression.
289 *
290 * @throws XPathExpressionException If the expression cannot be evaluated.
291 * @throws IllegalArgumentException If the implementation of this method
292 * does not support the
293 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
294 *
295 * @since 1.9
296 */
297 default XPathEvaluationResult<?> evaluateExpression(Object item)
298 throws XPathExpressionException
299 {
300 return evaluateExpression(item, XPathEvaluationResult.class);
301 }
302
303 /**
304 * Evaluate the compiled XPath expression in the specified context,
305 * and return the result with the type specified through the {@code class type}
306 * <p>
307 * This method builds a data model for the {@link InputSource} and calls
308 * {@link #evaluateExpression(Object item, Class type)} on the resulting
309 * document object.
310 * <P>
311 * By default, the JDK's data model is {@link org.w3c.dom.Document}.
312 *
313 * @implSpec
314 * The default implementation in the XPath API is equivalent to:
315 * <pre> {@code
316 (T)evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type));
317 * }</pre>
318 *
319 * Since the {@code evaluate} method does not support the
320 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
321 * XPathEvaluationResult as the type will result in IllegalArgumentException.
322 * Any implementation supporting the
323 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
324 * this method.
325 *
326 * @param <T> The class type that will be returned by the XPath expression.
327 * @param source The {@code InputSource} of the document to evaluate over.
328 * @param type The class type expected to be returned by the XPath expression.
329 *
330 * @return The result of evaluating the expression.
331 *
332 * @throws XPathExpressionException If the expression cannot be evaluated.
333 * @throws IllegalArgumentException If {@code type} is not of the types
334 * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType
335 * XPathResultType}, or XPathEvaluationResult is specified as the type but an
336 * implementation supporting the
337 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type
338 * is not available.
339 * @throws NullPointerException If {@code source or type} is {@code null}.
340 *
341 * @since 1.9
342 */
343 default <T>T evaluateExpression(InputSource source, Class<T> type)
344 throws XPathExpressionException
345 {
346 return type.cast(evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type)));
347 }
348
349 /**
350 * Evaluate the compiled XPath expression in the specified context. This is
351 * equivalent to calling {@link #evaluateExpression(InputSource source, Class type)}
352 * with type {@link XPathEvaluationResult}:
353 * <pre> {@code
354 * evaluateExpression(source, XPathEvaluationResult.class);
355 * }</pre>
356 *
357 * @implSpec
358 * The default implementation in the XPath API is equivalent to:
359 * <pre> {@code
360 * (XPathEvaluationResult)evaluateExpression(source, XPathEvaluationResult.class);
361 * }</pre>
362 *
363 * Since the {@code evaluate} method does not support the
364 * {@link XPathEvaluationResult.XPathResultType#ANY ANY}
365 * type, the default implementation of this method will always throw an
366 * IllegalArgumentException. Any implementation supporting the
367 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
368 * override this method.
369 *
370 * @param source The {@code InputSource} of the document to evaluate over.
371 *
372 * @return The result of evaluating the expression.
373 *
374 * @throws XPathExpressionException If the expression cannot be evaluated.
375 * @throws IllegalArgumentException If the implementation of this method
376 * does not support the
377 * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
378 * @throws NullPointerException If {@code source} is {@code null}.
379 *
380 * @since 1.9
381 */
382 default XPathEvaluationResult<?> evaluateExpression(InputSource source)
383 throws XPathExpressionException
384 {
385 return evaluateExpression(source, XPathEvaluationResult.class);
386 }
387 }