1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17// $Id: XPath.java 569998 2007-08-27 04:40:02Z mrglavas $
18
19package javax.xml.xpath;
20
21import javax.xml.namespace.NamespaceContext;
22import javax.xml.namespace.QName;
23import org.xml.sax.InputSource;
24
25/**
26 * <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
27 *
28 * <table id="XPath-evaluation" border="1" cellpadding="2">
29 *   <thead>
30 *     <tr>
31 *       <th colspan="2">Evaluation of XPath Expressions.</th>
32 *     </tr>
33 *   </thead>
34 *   <tbody>
35 *     <tr>
36 *       <td>context</td>
37 *       <td>
38 *         If a request is made to evaluate the expression in the absence
39 * of a context item, an empty document node will be used for the context.
40 * For the purposes of evaluating XPath expressions, a DocumentFragment
41 * is treated like a Document node.
42 *      </td>
43 *    </tr>
44 *    <tr>
45 *      <td>variables</td>
46 *      <td>
47 *        If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}
48 *        set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}.
49 *        An {@link XPathExpressionException} is raised if the variable resolver is undefined or
50 *        the resolver returns <code>null</code> for the variable.
51 *        The value of a variable must be immutable through the course of any single evaluation.</p>
52 *      </td>
53 *    </tr>
54 *    <tr>
55 *      <td>functions</td>
56 *      <td>
57 *        If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}
58 *        set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}.
59 *        An {@link XPathExpressionException} is raised if the function resolver is undefined or
60 *        the function resolver returns <code>null</code> for the function.</p>
61 *      </td>
62 *    </tr>
63 *    <tr>
64 *      <td>QNames</td>
65 *      <td>
66 *        QNames in the expression are resolved against the XPath namespace context
67 *        set with {@link #setNamespaceContext(NamespaceContext nsContext)}.
68 *      </td>
69 *    </tr>
70 *    <tr>
71 *      <td>result</td>
72 *      <td>
73 *        This result of evaluating an expression is converted to an instance of the desired return type.
74 *        Valid return types are defined in {@link XPathConstants}.
75 *        Conversion to the return type follows XPath conversion rules.</p>
76 *      </td>
77 *    </tr>
78 * </table>
79 *
80 * @author  <a href="Norman.Walsh@Sun.com">Norman Walsh</a>
81 * @author  <a href="Jeff.Suttor@Sun.com">Jeff Suttor</a>
82 * @version $Revision: 569998 $, $Date: 2007-08-26 21:40:02 -0700 (Sun, 26 Aug 2007) $
83 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>
84 * @since 1.5
85 */
86public interface XPath {
87
88    /**
89     * <p>Reset this <code>XPath</code> to its original configuration.</p>
90     *
91     * <p><code>XPath</code> is reset to the same state as when it was created with
92     * {@link XPathFactory#newXPath()}.
93     * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s
94     * thus saving resources associated with the creation of new <code>XPath</code>s.</p>
95     *
96     * <p>The reset <code>XPath</code> is not guaranteed to have the same {@link XPathFunctionResolver}, {@link XPathVariableResolver}
97     * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.
98     * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>, <code>XPathVariableResolver</code>
99     * and <code>NamespaceContext</code>.</p>
100     */
101    public void reset();
102
103    /**
104     * <p>Establish a variable resolver.</p>
105     *
106     * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
107     *
108     * @param resolver Variable resolver.
109     *
110     *  @throws NullPointerException If <code>resolver</code> is <code>null</code>.
111     */
112    public void setXPathVariableResolver(XPathVariableResolver resolver);
113
114    /**
115       * <p>Return the current variable resolver.</p>
116       *
117       * <p><code>null</code> is returned in no variable resolver is in effect.</p>
118       *
119       * @return Current variable resolver.
120       */
121    public XPathVariableResolver getXPathVariableResolver();
122
123    /**
124       * <p>Establish a function resolver.</p>
125       *
126       * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
127       *
128       * @param resolver XPath function resolver.
129       *
130       * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
131       */
132    public void setXPathFunctionResolver(XPathFunctionResolver resolver);
133
134    /**
135       * <p>Return the current function resolver.</p>
136       *
137       * <p><code>null</code> is returned in no function resolver is in effect.</p>
138       *
139       * @return Current function resolver.
140       */
141    public XPathFunctionResolver getXPathFunctionResolver();
142
143    /**
144       * <p>Establish a namespace context.</p>
145       *
146       * <p>A <code>NullPointerException</code> is thrown if <code>nsContext</code> is <code>null</code>.</p>
147       *
148       * @param nsContext Namespace context to use.
149       *
150       * @throws NullPointerException If <code>nsContext</code> is <code>null</code>.
151       */
152    public void setNamespaceContext(NamespaceContext nsContext);
153
154    /**
155       * <p>Return the current namespace context.</p>
156       *
157       * <p><code>null</code> is returned in no namespace context is in effect.</p>
158       *
159       * @return Current Namespace context.
160       */
161    public NamespaceContext getNamespaceContext();
162
163    /**
164       * <p>Compile an XPath expression for later evaluation.</p>
165       *
166       * <p>If <code>expression</code> contains any {@link XPathFunction}s,
167       * they must be available via the {@link XPathFunctionResolver}.
168       * An {@link XPathExpressionException} will be thrown if the <code>XPathFunction</code>
169       * cannot be resolved with the <code>XPathFunctionResolver</code>.</p>
170       *
171       * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is thrown.</p>
172       *
173       * @param expression The XPath expression.
174       *
175       * @return Compiled XPath expression.
176
177       * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
178       * @throws NullPointerException If <code>expression</code> is <code>null</code>.
179       */
180    public XPathExpression compile(String expression)
181        throws XPathExpressionException;
182
183    /**
184     * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as the specified type.</p>
185     *
186     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
187     * variable, function and <code>QName</code> resolution and return type conversion.</p>
188     *
189     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (
190     * {@link XPathConstants#NUMBER NUMBER},
191     * {@link XPathConstants#STRING STRING},
192     * {@link XPathConstants#BOOLEAN BOOLEAN},
193     * {@link XPathConstants#NODE NODE} or
194     * {@link XPathConstants#NODESET NODESET})
195     * then an <code>IllegalArgumentException</code> is thrown.</p>
196     *
197     * <p>If a <code>null</code> value is provided for
198     * <code>item</code>, an empty document will be used for the
199     * context.
200     * If <code>expression</code> or <code>returnType</code> is <code>null</code>, then a
201     * <code>NullPointerException</code> is thrown.</p>
202     *
203     * @param expression The XPath expression.
204     * @param item The starting context (node or node list, for example).
205     * @param returnType The desired return type.
206     *
207     * @return Result of evaluating an XPath expression as an <code>Object</code> of <code>returnType</code>.
208     *
209     * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
210     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
211     * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is <code>null</code>.
212     */
213    public Object evaluate(String expression, Object item, QName returnType)
214        throws XPathExpressionException;
215
216    /**
217     * <p>Evaluate an XPath expression in the specified context and return the result as a <code>String</code>.</p>
218     *
219     * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a <code>returnType</code> of
220     * {@link XPathConstants#STRING}.</p>
221     *
222     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
223     * variable, function and QName resolution and return type conversion.</p>
224     *
225     * <p>If a <code>null</code> value is provided for
226     * <code>item</code>, an empty document will be used for the
227     * context.
228     * If <code>expression</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
229     *
230     * @param expression The XPath expression.
231     * @param item The starting context (node or node list, for example).
232     *
233     * @return The <code>String</code> that is the result of evaluating the expression and
234     *   converting the result to a <code>String</code>.
235     *
236     * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
237     * @throws NullPointerException If <code>expression</code> is <code>null</code>.
238     */
239    public String evaluate(String expression, Object item)
240        throws XPathExpressionException;
241
242    /**
243     * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
244     * and return the result as the specified type.</p>
245     *
246     * <p>This method builds a data model for the {@link InputSource} and calls
247     * {@link #evaluate(String expression, Object item, QName returnType)} on the resulting document object.</p>
248     *
249     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
250     * variable, function and QName resolution and return type conversion.</p>
251     *
252     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
253     * then an <code>IllegalArgumentException</code> is thrown.</p>
254     *
255     * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is <code>null</code>,
256     * then a <code>NullPointerException</code> is thrown.</p>
257     *
258     * @param expression The XPath expression.
259     * @param source The input source of the document to evaluate over.
260     * @param returnType The desired return type.
261     *
262     * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
263     *
264     * @throws XPathExpressionException If expression cannot be evaluated.
265     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
266     * @throws NullPointerException If <code>expression</code>, <code>source</code> or <code>returnType</code>
267     *   is <code>null</code>.
268     */
269    public Object evaluate(
270        String expression,
271        InputSource source,
272        QName returnType)
273        throws XPathExpressionException;
274
275    /**
276     * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
277     * and return the result as a <code>String</code>.</p>
278     *
279     * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)} with a
280     * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
281     *
282     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
283     * variable, function and QName resolution and return type conversion.</p>
284     *
285     * <p>If <code>expression</code> or <code>source</code> is <code>null</code>,
286     * then a <code>NullPointerException</code> is thrown.</p>
287     *
288     * @param expression The XPath expression.
289     * @param source The <code>InputSource</code> of the document to evaluate over.
290     *
291     * @return The <code>String</code> that is the result of evaluating the expression and
292     *   converting the result to a <code>String</code>.
293     *
294     * @throws XPathExpressionException If expression cannot be evaluated.
295     * @throws NullPointerException If <code>expression</code> or <code>source</code> is <code>null</code>.
296     */
297    public String evaluate(String expression, InputSource source)
298        throws XPathExpressionException;
299}
300