XPath


1   // $Id: XPath.java,v 1.12.14.2.2.3 2004/07/01 17:49:22 ndw Exp $
2   
3   /*
4    * @(#)XPath.java   1.10 04/07/26
5    * 
6    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
7    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
8    */
9   
10  package javax.xml.xpath;
11  
12  import org.xml.sax.InputSource  ;
13  import javax.xml.namespace.QName  ;
14  import javax.xml.namespace.NamespaceContext  ;
15  
16  /**
17   * <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
18   *
19   * <table id="XPath-evaluation" border="1" cellpadding="2">
20   *   <thead>
21   *     <tr>
22   *       <th colspan="2">Evaluation of XPath Expressions.</th>
23   *     </tr>
24   *   </thead>
25   *   <tbody>
26   *     <tr>
27   *       <td>context</td>
28   *       <td>
29   *         If a request is made to evaluate the expression in the absence
30   * of a context item, an empty document node will be used for the context.
31   * For the purposes of evaluating XPath expressions, a DocumentFragment
32   * is treated like a Document node.
33   *      </td>
34   *    </tr>
35   *    <tr>
36   *      <td>variables</td>
37   *      <td>
38   *        If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}
39   *        set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}.
40   *        An {@link XPathExpressionException} is raised if the variable resolver is undefined or
41   *        the resolver returns <code>null</code> for the variable.
42   *        The value of a variable must be immutable through the course of any single evaluation.</p>
43   *      </td>
44   *    </tr>
45   *    <tr>
46   *      <td>functions</td>
47   *      <td>
48   *        If the expression contains a function reference, the function will be found through the {@link XPathFunctionResolver}
49   *        set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}.
50   *        An {@link XPathExpressionException} is raised if the function resolver is undefined or
51   *        the function resolver returns <code>null</code> for the function.</p>
52   *      </td>
53   *    </tr>
54   *    <tr>
55   *      <td>QNames</td>
56   *      <td>
57   *        QNames in the expression are resolved against the XPath namespace context
58   *        set with {@link #setNamespaceContext(NamespaceContext nsContext)}.
59   *      </td>
60   *    </tr>
61   *    <tr>
62   *      <td>result</td>
63   *      <td>
64   *        This result of evaluating an expression is converted to an instance of the desired return type.
65   *        Valid return types are defined in {@link XPathConstants}.
66   *        Conversion to the return type follows XPath conversion rules.</p>
67   *      </td>
68   *    </tr>
69   * </table>
70   * 
71   * @author  <a HREF="Norman.Walsh@Sun.com">Norman Walsh</a>
72   * @author  <a HREF="Jeff.Suttor@Sun.com">Jeff Suttor</a>
73   * @version $Revision: 1.12.14.2.2.3 $, $Date: 2004/07/01 17:49:22 $
74   * @see <a HREF="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>
75   * @since 1.5
76   */
77  public interface XPath {
78      
79      /**
80       * <p>Reset this <code>XPath</code> to its original configuration.</p>
81       * 
82       * <p><code>XPath</code> is reset to the same state as when it was created with
83       * {@link XPathFactory#newXPath()}.
84       * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s
85       * thus saving resources associated with the creation of new <code>XPath</code>s.</p>
86       * 
87       * <p>The reset <code>XPath</code> is not guaranteed to have the same {@link XPathFunctionResolver}, {@link XPathVariableResolver}
88       * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.
89       * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>, <code>XPathVariableResolver</code>
90       * and <code>NamespaceContext</code>.</p>
91       */
92      public void reset();
93  
94      /**
95       * <p>Establish a variable resolver.</p>
96       * 
97       * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
98       * 
99       * @param resolver Variable resolver.
100      * 
101      *  @throws NullPointerException If <code>resolver</code> is <code>null</code>.
102      */
103     public void setXPathVariableResolver(XPathVariableResolver   resolver);
104 
105     /**
106        * <p>Return the current variable resolver.</p>
107        * 
108        * <p><code>null</code> is returned in no variable resolver is in effect.</p>
109        *  
110        * @return Current variable resolver.
111        */
112     public XPathVariableResolver   getXPathVariableResolver();
113 
114     /**
115        * <p>Establish a function resolver.</p>
116        * 
117        * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
118        * 
119        * @param resolver XPath function resolver.
120        * 
121        * @throws NullPointerException If <code>resolver</code> is <code>null</code>.
122        */
123     public void setXPathFunctionResolver(XPathFunctionResolver   resolver);
124 
125     /**
126        * <p>Return the current function resolver.</p>
127        * 
128        * <p><code>null</code> is returned in no function resolver is in effect.</p>
129        * 
130        * @return Current function resolver.
131        */
132     public XPathFunctionResolver   getXPathFunctionResolver();
133 
134     /**
135        * <p>Establish a namespace context.</p>
136        * 
137        * <p>A <code>NullPointerException</code> is thrown if <code>nsContext</code> is <code>null</code>.</p>
138        * 
139        * @param nsContext Namespace context to use.
140        * 
141        * @throws NullPointerException If <code>nsContext</code> is <code>null</code>.
142        */
143     public void setNamespaceContext(NamespaceContext   nsContext);
144 
145     /**
146        * <p>Return the current namespace context.</p>
147        * 
148        * <p><code>null</code> is returned in no namespace context is in effect.</p>
149        * 
150        * @return Current Namespace context.
151        */
152     public NamespaceContext   getNamespaceContext();
153 
154     /** 
155        * <p>Compile an XPath expression for later evaluation.</p>
156        * 
157        * <p>If <code>expression</code> contains any {@link XPathFunction}s,
158        * they must be available via the {@link XPathFunctionResolver}.
159        * An {@link XPathExpressionException} will be thrown if the <code>XPathFunction</code>
160        * cannot be resovled with the <code>XPathFunctionResolver</code>.</p>
161        *  
162        * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is thrown.</p> 
163        *
164        * @param expression The XPath expression.
165        * 
166        * @return Compiled XPath expression.
167     
168        * @throws XPathExpressionException If <code>expression</code> cannot be compiled.
169        * @throws NullPointerException If <code>expression</code> is <code>null</code>.
170        */
171     public XPathExpression   compile(String   expression)
172         throws XPathExpressionException  ;
173 
174     /**
175      * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as the specified type.</p>
176      *
177      * <p>See <a HREF="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
178      * variable, function and <code>QName</code> resolution and return type conversion.</p>
179      * 
180      * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (
181      * {@link XPathConstants#NUMBER NUMBER},
182      * {@link XPathConstants#STRING STRING},
183      * {@link XPathConstants#BOOLEAN BOOLEAN},
184      * {@link XPathConstants#NODE NODE} or
185      * {@link XPathConstants#NODESET NODESET})
186      * then an <code>IllegalArgumentException</code> is thrown.</p>
187      * 
188      * <p>If a <code>null</code> value is provided for 
189      * <code>item</code>, an empty document will be used for the
190      * context.
191      * If <code>expression</code> or <code>returnType</code> is <code>null</code>, then a
192      * <code>NullPointerException</code> is thrown.</p>
193      *
194      * @param expression The XPath expression.
195      * @param item The starting context (node or node list, for example).
196      * @param returnType The desired return type.
197      * 
198      * @return Result of evaluating an XPath expression as an <code>Object</code> of <code>returnType</code>.
199      * 
200      * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
201      * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
202      * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is <code>null</code>.
203      */
204     public Object   evaluate(String   expression, Object   item, QName   returnType)
205         throws XPathExpressionException  ;
206 
207     /**
208      * <p>Evaluate an XPath expression in the specified context and return the result as a <code>String</code>.</p>
209      *
210      * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a <code>returnType</code> of
211      * {@link XPathConstants#STRING}.</p>
212      * 
213      * <p>See <a HREF="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
214      * variable, function and QName resolution and return type conversion.</p>
215      *
216      * <p>If a <code>null</code> value is provided for 
217      * <code>item</code>, an empty document will be used for the
218      * context.
219      * If <code>expression</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>
220      * 
221      * @param expression The XPath expression.
222      * @param item The starting context (node or node list, for example).
223      * 
224      * @return The <code>String</code> that is the result of evaluating the expression and
225      *   converting the result to a <code>String</code>.
226      * 
227      * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.
228      * @throws NullPointerException If <code>expression</code> is <code>null</code>.
229      */
230     public String   evaluate(String   expression, Object   item)
231         throws XPathExpressionException  ;
232 
233     /**
234      * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
235      * and return the result as the specified type.</p>
236      *
237      * <p>This method builds a data model for the {@link InputSource} and calls
238      * {@link #evaluate(String expression, Object item, QName returnType)} on the resulting document object.</p>
239      *
240      * <p>See <a HREF="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
241      * variable, function and QName resolution and return type conversion.</p>
242      * 
243      * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},
244      * then an <code>IllegalArgumentException</code> is thrown.</p>
245      * 
246      * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is <code>null</code>,
247      * then a <code>NullPointerException</code> is thrown.</p>
248      * 
249      * @param expression The XPath expression.
250      * @param source The input source of the document to evaluate over.
251      * @param returnType The desired return type.
252      * 
253      * @return The <code>Object</code> that encapsulates the result of evaluating the expression.
254      * 
255      * @throws XPathExpressionException If expression cannot be evaluated.
256      * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.
257      * @throws NullPointerException If <code>expression</code>, <code>source</code> or <code>returnType</code>
258      *   is <code>null</code>.
259      */
260     public Object   evaluate(
261         String   expression,
262         InputSource   source,
263         QName   returnType)
264         throws XPathExpressionException  ;
265 
266     /**
267      * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>
268      * and return the result as a <code>String</code>.</p>
269      *
270      * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)} with a
271      * <code>returnType</code> of {@link XPathConstants#STRING}.</p>
272      *
273      * <p>See <a HREF="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,
274      * variable, function and QName resolution and return type conversion.</p>
275      * 
276      * <p>If <code>expression</code> or <code>source</code> is <code>null</code>,
277      * then a <code>NullPointerException</code> is thrown.</p>
278      * 
279      * @param expression The XPath expression.
280      * @param source The <code>InputSource</code> of the document to evaluate over.
281      * 
282      * @return The <code>String</code> that is the result of evaluating the expression and
283      *   converting the result to a <code>String</code>.
284      * 
285      * @throws XPathExpressionException If expression cannot be evaluated.
286      * @throws NullPointerException If <code>expression</code> or <code>source</code> is <code>null</code>.
287      */
288     public String   evaluate(String   expression, InputSource   source)
289         throws XPathExpressionException  ;
290 }
291
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