XPathExpression.java revision 692:b13f7d2000cf 
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25
26package javax.xml.xpath;
27
28import javax.xml.namespace.QName;
29import org.xml.sax.InputSource;
30
31/**
32 * <p>{@code XPathExpression} provides access to compiled XPath expressions.</p>
33 *
34 * <a name="XPathExpression-evaluation"/>
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.</p>
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.</p>
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.</p>
80 *      </td>
81 *    </tr>
82 * </table>
83 *
84 * <p>An XPath expression is not thread-safe and not reentrant.
85 * In other words, it is the application's responsibility to make
86 * sure that one {@link XPathExpression} object is not used from
87 * more than one thread at any given time, and while the {@code evaluate}
88 * method is invoked, applications may not recursively call
89 * the {@code evaluate} method.
90 * <p>
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 */
97public interface XPathExpression {
98
99
100    /**
101     * <p>Evaluate the compiled XPath expression in the specified context and return the result as the specified type.</p>
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.</p>
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     * <p>Evaluate the compiled XPath expression in the specified context and return the result as a {@code String}.</p>
130     *
131     * <p>This method calls {@link #evaluate(Object item, QName returnType)} with a {@code returnType} of
132     * {@link XPathConstants#STRING}.</p>
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.</p>
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     * <p>Evaluate the compiled XPath expression in the context of the specified {@code InputSource} and return the result as the
157     * specified type.</p>
158     *
159     * <p>This method builds a data model for the {@link InputSource} and calls
160     * {@link #evaluate(Object item, QName returnType)} on the resulting document object.</p>
161     *
162     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
163     * variable, function and QName resolution and return type conversion.</p>
164     *
165     * <p>If {@code returnType} is not one of the types defined in {@link XPathConstants},
166     * then an {@code IllegalArgumentException} is thrown.</p>
167     *
168     * <p>If {@code source} or {@code returnType} is {@code null},
169     * then a {@code NullPointerException} is thrown.</p>
170     *
171     * @param source The {@code InputSource} of the document to evaluate over.
172     * @param returnType The desired return type.
173     *
174     * @return The {@code Object} that is the result of evaluating the expression and converting the result to
175     *   {@code returnType}.
176     *
177     * @throws XPathExpressionException If the expression cannot be evaluated.
178     * @throws IllegalArgumentException If {@code returnType} is not one of the types defined in {@link XPathConstants}.
179     * @throws NullPointerException If {@code source or returnType} is {@code null}.
180     */
181    public Object evaluate(InputSource source, QName returnType)
182        throws XPathExpressionException;
183
184    /**
185     * <p>Evaluate the compiled XPath expression in the context of the specified {@code InputSource} and return the result as a
186     * {@code String}.</p>
187     *
188     * <p>This method calls {@link #evaluate(InputSource source, QName returnType)} with a {@code returnType} of
189     * {@link XPathConstants#STRING}.</p>
190     *
191     * <p>See <a href="#XPathExpression-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
192     * variable, function and QName resolution and return type conversion.</p>
193     *
194     * <p>If {@code source} is {@code null}, then a {@code NullPointerException} is thrown.</p>
195     *
196     * @param source The {@code InputSource} of the document to evaluate over.
197     *
198     * @return The {@code String} that is the result of evaluating the expression and converting the result to a
199     *   {@code String}.
200     *
201     * @throws XPathExpressionException If the expression cannot be evaluated.
202     * @throws NullPointerException If {@code source} is {@code null}.
203     */
204    public String evaluate(InputSource source)
205        throws XPathExpressionException;
206
207    /**
208     * Evaluate the compiled XPath expression in the specified context, and return
209     * the result with the type specified through the {@code class type}.
210     *
211     * <p>
212     * The parameter {@code item} represents the context the XPath expression
213     * will be operated on. The type of the context is implementation-dependent.
214     * If the value is {@code null}, the operation must have no dependency on
215     * the context, otherwise an XPathExpressionException will be thrown.
216     *
217     * @implNote
218     * The type of the context is usually {@link org.w3c.dom.Node}.
219     *
220     * @implSpec
221     * The default implementation in the XPath API is equivalent to:
222     * <pre> {@code
223     *     (T)evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type));
224     * }</pre>
225     *
226     * Since the {@code evaluate} method does not support the
227     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
228     * XPathEvaluationResult as the type will result in IllegalArgumentException.
229     * Any implementation supporting the
230     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
231     * this method.
232     *
233     * @param <T> The class type that will be returned by the XPath expression.
234     * @param item The context the XPath expression will be evaluated in.
235     * @param type The class type expected to be returned by the XPath expression.
236     *
237     * @return The result of evaluating the expression.
238     *
239     * @throws XPathExpressionException If the expression cannot be evaluated.
240     * @throws IllegalArgumentException If {@code type} is not of the types
241     * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType
242     * XPathResultType}, or XPathEvaluationResult is specified as the type but an
243     * implementation supporting the
244     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type is not available.
245     * @throws NullPointerException If {@code type} is {@code null}.
246     *
247     * @since 1.9
248     */
249    default <T>T evaluateExpression(Object item, Class<T> type)
250        throws XPathExpressionException
251    {
252        return type.cast(evaluate(item, XPathEvaluationResult.XPathResultType.getQNameType(type)));
253    }
254
255    /**
256     * Evaluate the compiled XPath expression in the specified context. This is
257     * equivalent to calling {@link #evaluateExpression(Object item, Class type)}
258     * with type {@link XPathEvaluationResult}:
259     * <pre> {@code
260     *     evaluateExpression(item, XPathEvaluationResult.class);
261     * }</pre>
262     * <p>
263     * The parameter {@code item} represents the context the XPath expression
264     * will be operated on. The type of the context is implementation-dependent.
265     * If the value is {@code null}, the operation must have no dependency on
266     * the context, otherwise an XPathExpressionException will be thrown.
267     *
268     * @implNote
269     * The type of the context is usually {@link org.w3c.dom.Node}.
270     *
271     * @implSpec
272     * The default implementation in the XPath API is equivalent to:
273     * <pre> {@code
274     *     evaluateExpression(item, XPathEvaluationResult.class);
275     * }</pre>
276     *
277     * Since the {@code evaluate} method does not support the
278     * {@link XPathEvaluationResult.XPathResultType#ANY ANY}
279     * type, the default implementation of this method will always throw an
280     * IllegalArgumentException. Any implementation supporting the
281     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
282     * override this method.
283     *
284     * @param item The context the XPath expression will be evaluated in.
285     *
286     * @return The result of evaluating the expression.
287     *
288     * @throws XPathExpressionException If the expression cannot be evaluated.
289     * @throws IllegalArgumentException If the implementation of this method
290     * does not support the
291     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
292     *
293     * @since 1.9
294     */
295    default XPathEvaluationResult<?> evaluateExpression(Object item)
296        throws XPathExpressionException
297    {
298        return evaluateExpression(item, XPathEvaluationResult.class);
299    }
300
301    /**
302     * Evaluate the compiled XPath expression in the specified context,
303     * and return the result with the type specified through the {@code class type}
304     * <p>
305     * This method builds a data model for the {@link InputSource} and calls
306     * {@link #evaluateExpression(Object item, Class type)} on the resulting
307     * document object.
308     * <P>
309     * By default, the JDK's data model is {@link org.w3c.dom.Document}.
310     *
311     * @implSpec
312     * The default implementation in the XPath API is equivalent to:
313     * <pre> {@code
314           (T)evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type));
315     * }</pre>
316     *
317     * Since the {@code evaluate} method does not support the
318     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying
319     * XPathEvaluationResult as the type will result in IllegalArgumentException.
320     * Any implementation supporting the
321     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override
322     * this method.
323     *
324     * @param <T> The class type that will be returned by the XPath expression.
325     * @param source The {@code InputSource} of the document to evaluate over.
326     * @param type The class type expected to be returned by the XPath expression.
327     *
328     * @return The result of evaluating the expression.
329     *
330     * @throws XPathExpressionException If the expression cannot be evaluated.
331     * @throws IllegalArgumentException If {@code type} is not of the types
332     * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType
333     * XPathResultType}, or XPathEvaluationResult is specified as the type but an
334     * implementation supporting the
335     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type
336     * is not available.
337     * @throws NullPointerException If {@code source or type} is {@code null}.
338     *
339     * @since 1.9
340     */
341    default <T>T evaluateExpression(InputSource source, Class<T> type)
342        throws XPathExpressionException
343    {
344        return type.cast(evaluate(source, XPathEvaluationResult.XPathResultType.getQNameType(type)));
345    }
346
347    /**
348     * Evaluate the compiled XPath expression in the specified context. This is
349     * equivalent to calling {@link #evaluateExpression(InputSource source, Class type)}
350     * with type {@link XPathEvaluationResult}:
351     * <pre> {@code
352     *     evaluateExpression(source, XPathEvaluationResult.class);
353     * }</pre>
354     * <p>
355     *
356     * @implSpec
357     * The default implementation in the XPath API is equivalent to:
358     * <pre> {@code
359     *     (XPathEvaluationResult)evaluateExpression(source, XPathEvaluationResult.class);
360     * }</pre>
361     *
362     * Since the {@code evaluate} method does not support the
363     * {@link XPathEvaluationResult.XPathResultType#ANY ANY}
364     * type, the default implementation of this method will always throw an
365     * IllegalArgumentException. Any implementation supporting the
366     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore
367     * override this method.
368     *
369     * @param source The {@code InputSource} of the document to evaluate over.
370     *
371     * @return The result of evaluating the expression.
372     *
373     * @throws XPathExpressionException If the expression cannot be evaluated.
374     * @throws IllegalArgumentException If the implementation of this method
375     * does not support the
376     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.
377     * @throws NullPointerException If {@code source} is {@code null}.
378     *
379     * @since 1.9
380     */
381    default XPathEvaluationResult<?> evaluateExpression(InputSource source)
382        throws XPathExpressionException
383    {
384        return evaluateExpression(source, XPathEvaluationResult.class);
385    }
386}
387