1 /*
2 * Copyright (c) 2003, 2005, 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
6 * under the terms of the GNU General Public License version 2 only, as
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).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.xml.xpath;
27
28 import org.xml.sax.InputSource;
29 import javax.xml.namespace.QName;
30 import javax.xml.namespace.NamespaceContext;
31
32 /**
33 * <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
34 *
35 * <a name="XPath-evaluation"/>
36 * <table border="1" cellpadding="2">
37 * <thead>
38 * <tr>
39 * <th colspan="2">Evaluation of XPath Expressions.</th>
40 * </tr>
41 * </thead>
42 * <tbody>
43 * <tr>
44 * <td>context</td>
45 * <td>
46 * If a request is made to evaluate the expression in the absence
47 * of a context item, an empty document node will be used for the context.
48 * For the purposes of evaluating XPath expressions, a DocumentFragment
49 * is treated like a Document node.
50 * </td>
51 * </tr>
52 * <tr>
53 * <td>variables</td>
54 * <td>
55 * If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}
56 * set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}.
57 * An {@link XPathExpressionException} is raised if the variable resolver is undefined or
58 * the resolver returns <code>null</code> for the variable.
59 * The value of a variable must be immutable through the course of any single evaluation.</p>
60 * </td>
61 * </tr>
62 * <tr>
63 * <td>functions</td>
64 * <td>
65 * If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}
66 * set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}.
67 * An {@link XPathExpressionException} is raised if the function resolver is undefined or
68 * the function resolver returns <code>null</code> for the function.</p>
69 * </td>
70 * </tr>
71 * <tr>
72 * <td>QNames</td>
73 * <td>
74 * QNames in the expression are resolved against the XPath namespace context
75 * set with {@link #setNamespaceContext(NamespaceContext nsContext)}.
76 * </td>
77 * </tr>
78 * <tr>
79 * <td>result</td>
80 * <td>
81 * This result of evaluating an expression is converted to an instance of the desired return type.
82 * Valid return types are defined in {@link XPathConstants}.
83 * Conversion to the return type follows XPath conversion rules.</p>
84 * </td>
85 * </tr>
86 * </table>
87 *
88 * <p>An XPath object is not thread-safe and not reentrant.
89 * In other words, it is the application's responsibility to make
90 * sure that one {@link XPath} object is not used from
91 * more than one thread at any given time, and while the <code>evaluate</code>
92 * method is invoked, applications may not recursively call
93 * the <code>evaluate</code> method.
94 * <p>
95 *
96 * @author <a href="Norman.Walsh@Sun.com">Norman Walsh</a>
97 * @author <a href="Jeff.Suttor@Sun.com">Jeff Suttor</a>
98 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>
99 * @since 1.5
100 */
101 public interface XPath {
102
103 /**
104 * <p>Reset this <code>XPath</code> to its original configuration.</p>
105 *
106 * <p><code>XPath</code> is reset to the same state as when it was created with
107 * {@link XPathFactory#newXPath()}.
108 * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s
109 * thus saving resources associated with the creation of new <code>XPath</code>s.</p>
110 *
111 * <p>The reset <code>XPath</code> is not guaranteed to have the same {@link XPathFunctionResolver}, {@link XPathVariableResolver}
112 * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.
113 * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>, <code>XPathVariableResolver</code>
114 * and <code>NamespaceContext</code>.</p>
115 */
116 public void reset();
117
118 /**
119 * <p>Establish a variable resolver.</p>
120 *
121 * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
122 *
123 * @param resolver Variable resolver.
124 *
125 * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
126 */
127 public void setXPathVariableResolver(XPathVariableResolver resolver);
128
129 /**
130 * <p>Return the current variable resolver.</p>
131 *
132 * <p><code>null</code> is returned in no variable resolver is in effect.</p>
133 *
134 * @return Current variable resolver.
135 */
136 public XPathVariableResolver getXPathVariableResolver();
137
138 /**
139 * <p>Establish a function resolver.</p>
140 *
141 * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
142 *
143 * @param resolver XPath function resolver.
144 *
145 * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
146 */
147 public void setXPathFunctionResolver(XPathFunctionResolver resolver);
148
149 /**
150 * <p>Return the current function resolver.</p>
151 *
152 * <p><code>null</code> is returned in no function resolver is in effect.</p>
153 *
154 * @return Current function resolver.
155 */
156 public XPathFunctionResolver getXPathFunctionResolver();
157
158 /**
159 * <p>Establish a namespace context.</p>
160 *
161 * <p>A <code>NullPointerException</code> is thrown if <code>nsContext</code> is <code>null</code>.</p>
162 *
163 * @param nsContext Namespace context to use.
164 *
165 * @throws NullPointerException If <code>nsContext</code> is <code>null</code>.
166 */
167 public void setNamespaceContext(NamespaceContext nsContext);
168
169 /**
170 * <p>Return the current namespace context.</p>
171 *
172 * <p><code>null</code> is returned in no namespace context is in effect.</p>
173 *
174 * @return Current Namespace context.
175 */
176 public NamespaceContext getNamespaceContext();
177
178 /**
179 * <p>Compile an XPath expression for later evaluation.</p>
180 *
181 * <p>If <code>expression</code> contains any {@link XPathFunction}s,
182 * they must be available via the {@link XPathFunctionResolver}.
183 * An {@link XPathExpressionException} will be thrown if the
184 * <code>XPathFunction</code>
185 * cannot be resovled with the <code>XPathFunctionResolver</code>.</p>
186 *
187 * <p>If <code>expression</code> contains any variables, the
188 * {@link XPathVariableResolver} in effect
189 * <strong>at compile time</strong> will be used to resolve them.</p>
190 *
191 * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is thrown.</p>
192 *
193 * @param expression The XPath expression.
194 *
195 * @return Compiled XPath expression.
196
197 * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
198 * @throws NullPointerException If <code>expression</code> is <code>null</code>.
199 */
200 public XPathExpression compile(String expression)
201 throws XPathExpressionException;
202
203 /**
204 * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as the specified type.</p>
205 *
206 * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
207 * variable, function and <code>QName</code> resolution and return type conversion.</p>
208 *
209 * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (
210 * {@link XPathConstants#NUMBER NUMBER},
211 * {@link XPathConstants#STRING STRING},
212 * {@link XPathConstants#BOOLEAN BOOLEAN},
213 * {@link XPathConstants#NODE NODE} or
214 * {@link XPathConstants#NODESET NODESET})
215 * then an <code>IllegalArgumentException</code> is thrown.</p>
216 *
217 * <p>If a <code>null</code> value is provided for
218 * <code>item</code>, an empty document will be used for the
219 * context.
220 * If <code>expression</code> or <code>returnType</code> is <code>null</code>, then a
221 * <code>NullPointerException</code> is thrown.</p>
222 *
223 * @param expression The XPath expression.
224 * @param item The starting context (a node, for example).
225 * @param returnType The desired return type.
226 *
227 * @return Result of evaluating an XPath expression as an <code>Object</code> of <code>returnType</code>.
228 *
229 * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
230 * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
231 * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is <code>null</code>.
232 */
233 public Object evaluate(String expression, Object item, QName returnType)
234 throws XPathExpressionException;
235
236 /**
237 * <p>Evaluate an XPath expression in the specified context and return the result as a <code>String</code>.</p>
238 *
239 * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a <code>returnType</code> of
240 * {@link XPathConstants#STRING}.</p>
241 *
242 * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
243 * variable, function and QName resolution and return type conversion.</p>
244 *
245 * <p>If a <code>null</code> value is provided for
246 * <code>item</code>, an empty document will be used for the
247 * context.
248 * If <code>expression</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
249 *
250 * @param expression The XPath expression.
251 * @param item The starting context (a node, for example).
252 *
253 * @return The <code>String</code> that is the result of evaluating the expression and
254 * converting the result to a <code>String</code>.
255 *
256 * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
257 * @throws NullPointerException If <code>expression</code> is <code>null</code>.
258 */
259 public String evaluate(String expression, Object item)
260 throws XPathExpressionException;
261
262 /**
263 * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
264 * and return the result as the specified type.</p>
265 *
266 * <p>This method builds a data model for the {@link InputSource} and calls
267 * {@link #evaluate(String expression, Object item, QName returnType)} on the resulting document object.</p>
268 *
269 * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
270 * variable, function and QName resolution and return type conversion.</p>
271 *
272 * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
273 * then an <code>IllegalArgumentException</code> is thrown.</p>
274 *
275 * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is <code>null</code>,
276 * then a <code>NullPointerException</code> is thrown.</p>
277 *
278 * @param expression The XPath expression.
279 * @param source The input source of the document to evaluate over.
280 * @param returnType The desired return type.
281 *
282 * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
283 *
284 * @throws XPathExpressionException If expression cannot be evaluated.
285 * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
286 * @throws NullPointerException If <code>expression</code>, <code>source</code> or <code>returnType</code>
287 * is <code>null</code>.
288 */
289 public Object evaluate(
290 String expression,
291 InputSource source,
292 QName returnType)
293 throws XPathExpressionException;
294
295 /**
296 * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
297 * and return the result as a <code>String</code>.</p>
298 *
299 * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)} with a
300 * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
301 *
302 * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
303 * variable, function and QName resolution and return type conversion.</p>
304 *
305 * <p>If <code>expression</code> or <code>source</code> is <code>null</code>,
306 * then a <code>NullPointerException</code> is thrown.</p>
307 *
308 * @param expression The XPath expression.
309 * @param source The <code>InputSource</code> of the document to evaluate over.
310 *
311 * @return The <code>String</code> that is the result of evaluating the expression and
312 * converting the result to a <code>String</code>.
313 *
314 * @throws XPathExpressionException If expression cannot be evaluated.
315 * @throws NullPointerException If <code>expression</code> or <code>source</code> is <code>null</code>.
316 */
317 public String evaluate(String expression, InputSource source)
318 throws XPathExpressionException;
319 }