265 <h3>4. XPath Context</h3>
 266 
 267 <p>XPath location paths may be relative to a particular node in the
 268 document, known as the <code>context</code>. A context consists of:
 269 <ul>
 270     <li>a node (the context node)</li>
 271     <li>a pair of non-zero positive integers (the context position and the context size)</li>
 272     <li>a set of variable bindings</li>
 273     <li>a function library</li>
 274     <li>the set of namespace declarations in scope for the expression</li>    
 275 </ul>
 276 
 277 <p>
 278 It is an XML document tree represented as a hierarchy of nodes, a 
 279 {@link org.w3c.dom.Node} for example, in the JDK implementation.
 280 
 281 <a name="XPath.Use"></a>
 282 <h3>5. Using the XPath API</h3>
 283 
 284 Consider the following XML document:
 285 <p>
 286 <blockquote>
 287 <pre>
 288 &lt;widgets&gt;
 289 &lt;widget&gt;
 290 &lt;manufacturer/&gt;
 291 &lt;dimensions/&gt;
 292 &lt;/widget&gt;
 293 &lt;/widgets&gt;
 294 </pre>
 295 </blockquote>
 296 
 297 <p>
 298 The <code>&lt;widget&gt;</code> element can be selected with the following process:
 299 
 300 <blockquote>
 301 <pre>
 302 // parse the XML as a W3C Document
 303 DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
 304 Document document = builder.parse(new File("/widgets.xml"));
 305 

 349 In the above cases, the type of the expected results are known. In case where
 350 the result type is unknown or any type, the {@link javax.xml.xpath.XPathEvaluationResult}
 351 may be used to determine the return type. The following code demonstrates the usage:
 352 <blockquote>
 353 <pre>
 354 XPathEvaluationResult&lt;?&gt; result = xpath.evaluateExpression(expression, document);
 355 switch (result.type()) {
 356     case NODESET:
 357         XPathNodes nodes = (XPathNodes)result.value();
 358         ...
 359         break;
 360 }
 361 </pre>
 362 </blockquote>
 363 
 364 <p>
 365 The XPath 1.0 Number data type is defined as a double. However, the XPath 
 366 specification also provides functions that returns Integer type. To facilitate
 367 such operations, the XPath API allows Integer and Long to be used in 
 368 {@code evaluateExpression} method such as the following code: 
 369 <p>
 370 <blockquote>
 371 <pre>
 372 int count = xpath.evaluate("count(/widgets/widget)", document, Integer.class);
 373 </pre>
 374 </blockquote>
 375 
 376 @since 1.5
 377 
 378 </body>
 379 </html>

 265 <h3>4. XPath Context</h3>
 266 
 267 <p>XPath location paths may be relative to a particular node in the
 268 document, known as the <code>context</code>. A context consists of:
 269 <ul>
 270     <li>a node (the context node)</li>
 271     <li>a pair of non-zero positive integers (the context position and the context size)</li>
 272     <li>a set of variable bindings</li>
 273     <li>a function library</li>
 274     <li>the set of namespace declarations in scope for the expression</li>    
 275 </ul>
 276 
 277 <p>
 278 It is an XML document tree represented as a hierarchy of nodes, a 
 279 {@link org.w3c.dom.Node} for example, in the JDK implementation.
 280 
 281 <a name="XPath.Use"></a>
 282 <h3>5. Using the XPath API</h3>
 283 
 284 Consider the following XML document:

 285 <blockquote>
 286 <pre>
 287 &lt;widgets&gt;
 288 &lt;widget&gt;
 289 &lt;manufacturer/&gt;
 290 &lt;dimensions/&gt;
 291 &lt;/widget&gt;
 292 &lt;/widgets&gt;
 293 </pre>
 294 </blockquote>
 295 
 296 <p>
 297 The <code>&lt;widget&gt;</code> element can be selected with the following process:
 298 
 299 <blockquote>
 300 <pre>
 301 // parse the XML as a W3C Document
 302 DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
 303 Document document = builder.parse(new File("/widgets.xml"));
 304 

 348 In the above cases, the type of the expected results are known. In case where
 349 the result type is unknown or any type, the {@link javax.xml.xpath.XPathEvaluationResult}
 350 may be used to determine the return type. The following code demonstrates the usage:
 351 <blockquote>
 352 <pre>
 353 XPathEvaluationResult&lt;?&gt; result = xpath.evaluateExpression(expression, document);
 354 switch (result.type()) {
 355     case NODESET:
 356         XPathNodes nodes = (XPathNodes)result.value();
 357         ...
 358         break;
 359 }
 360 </pre>
 361 </blockquote>
 362 
 363 <p>
 364 The XPath 1.0 Number data type is defined as a double. However, the XPath 
 365 specification also provides functions that returns Integer type. To facilitate
 366 such operations, the XPath API allows Integer and Long to be used in 
 367 {@code evaluateExpression} method such as the following code: 

 368 <blockquote>
 369 <pre>
 370 int count = xpath.evaluate("count(/widgets/widget)", document, Integer.class);
 371 </pre>
 372 </blockquote>
 373 
 374 @since 1.5
 375 
 376 </body>
 377 </html>