luni/src/main/java/javax/xml/xpath/package.html - platform/libcore-snapshot - Git at Google

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- $Id: package.html 570107 2007-08-27 13:30:19Z mrglavas $ -->

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
                       "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml">
 <head>
 <title>javax.xml.xpath</title>
 <meta name="@author" content="mailto:Ben@galbraiths.org" />
 <meta name="@author" content="mailto:Norman.Walsh@Sun.com" />
 <meta name="@author" content="mailto:Jeff.Suttor@Sun.com" />
 <meta name="@version" content="$Revision: 570107 $, $Date: 2007-08-27 06:30:19 -0700 (Mon, 27 Aug 2007) $" />
 <meta name="@see" content="http://www.w3.org/TR/xpath" />
 <meta name="@since" content="1.5" />
 </head>

 <body>

 <p>This package provides an <em>object-model neutral</em> API for the
 evaluation of XPath expressions and access to the evaluation
 environment.
 </p>

 <p>The following XML standards apply:</p>

 <ul>
 <li><a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a></li>
 </ul>

 <hr />

 <h2>XPath Overview</h2>

 <p>The XPath language provides a simple, concise syntax for selecting
 nodes from an XML document. XPath also provides rules for converting a
 node in an XML document object model (DOM) tree to a boolean, double,
 or string value. XPath is a W3C-defined language and an official W3C
 recommendation; the W3C hosts the XML Path Language (XPath) Version
 1.0 specification.
 </p>

 <p>XPath started in life in 1999 as a supplement to the XSLT and
 XPointer languages, but has more recently become popular as a
 stand-alone language, as a single XPath expression can be used to
 replace many lines of DOM API code.
 </p>

 <h3>XPath Expressions</h3>

 <p>An XPath <em>expression</em> is composed of a <em>location
 path</em> and one or more optional <em>predicates</em>. Expressions
 may also include XPath variables.
 </p>

 <p>The following is an example of a simple XPath expression:</p>

 <pre>
 /foo/bar
 </pre>

 <p>This example would select the <code>&lt;bar&gt;</code> element in
 an XML document such as the following:</p>

 <pre>
 &lt;foo&gt;
 &lt;bar/&gt;
 &lt;/foo&gt;
 </pre>

 <p>The expression <code>/foo/bar</code> is an example of a location
 path. While XPath location paths resemble Unix-style file system
 paths, an important distinction is that XPath expressions return
 <em>all</em> nodes that match the expression. Thus, all three
 <code>&lt;bar&gt;</code> elements in the following document would be
 selected by the <code>/foo/bar</code> expression:</p>

 <pre>
 &lt;foo&gt;
 &lt;bar/&gt;
 &lt;bar/&gt;
 &lt;bar/&gt;
 &lt;/foo&gt;
 </pre>

 <p>A special location path operator, <code>//</code>, selects nodes at
 any depth in an XML document. The following example selects all
 <code>&lt;bar&gt;</code> elements regardless of their location in a
 document:</p>

 <pre>
 //bar
 </pre>

 <p>A wildcard operator, *, causes all element nodes to be selected.
 The following example selects all children elements of a
 <code>&lt;foo&gt;</code> element:</p>

 <pre>
 /foo/*
 </pre>

 <p>In addition to element nodes, XPath location paths may also address
 attribute nodes, text nodes, comment nodes, and processing instruction
 nodes. The following table gives examples of location paths for each
 of these node types:</p>

 <table border="1">
 <tr>
 <td>Location Path</td>
 <td>Description</td>
 </tr>
 <tr>
 <td>
 <code>/foo/bar/<strong>@id</strong></code>
 </td>
 <td>Selects the attribute <code>id</code> of the <code>&lt;bar&gt;</code> element
 </td>
 </tr>
 <tr>
 <td><code>/foo/bar/<strong>text()</strong></code>
 </td>
 <td>Selects the text nodes of the <code>&lt;bar&gt;</code> element. No
 distinction is made between escaped and non-escaped character data.
 </td>
 </tr>
 <tr>
 <td><code>/foo/bar/<strong>comment()</strong></code>
 </td>
 <td>Selects all comment nodes contained in the <code>&lt;bar&gt;</code> element.
 </td>
 </tr>
 <tr>
 <td><code>/foo/bar/<strong>processing-instruction()</strong></code>
 </td>
 <td>Selects all processing-instruction nodes contained in the
 <code>&lt;bar&gt;</code> element.
 </td>
 </tr>
 </table>

 <p>Predicates allow for refining the nodes selected by an XPath
 location path. Predicates are of the form
 <code>[<em>expression</em>]</code>. The following example selects all
 <code>&lt;foo&gt;</code> elements that contain an <code>include</code>
 attribute with the value of <code>true</code>:</p>

 <pre>
 //foo[@include='true']
 </pre>

 <p>Predicates may be appended to each other to further refine an
 expression, such as:</p>

 <pre>
 //foo[@include='true'][@mode='bar']
 </pre>

 <h3>Using the XPath API</h3>

 <p>
 The following example demonstrates using the XPath API to select one
 or more nodes from an XML document:</p>

 <pre>
 XPath xpath = XPathFactory.newInstance().newXPath();
 String expression = "/widgets/widget";
 InputSource inputSource = new InputSource("widgets.xml");
 NodeSet nodes = (NodeSet) xpath.evaluate(expression, inputSource, XPathConstants.NODESET);
 </pre>

 <h3>XPath Expressions and Types</h3>

 <p>While XPath expressions select nodes in the XML document, the XPath
 API allows the selected nodes to be coalesced into one of the
 following other data types:</p>

 <ul>
 <li><code>Boolean</code></li>
 <li><code>Number</code></li>
 <li><code>String</code></li>
 </ul>

 <p>The desired return type is specified by a {@link
 javax.xml.namespace.QName} parameter in method call used to evaluate
 the expression, which is either a call to
 <code>XPathExpression.evaluate(...)</code> or to one of the
 <code>XPath.evaluate(...)</code> convenience methods. The allowed
 QName values are specified as constants in the {@link
 javax.xml.xpath.XPathConstants} class; they are:</p>

 <ul>
 <li>{@link javax.xml.xpath.XPathConstants#NODESET}</li>
 <li>{@link javax.xml.xpath.XPathConstants#NODE}</li>
 <li>{@link javax.xml.xpath.XPathConstants#STRING}</li>
 <li>{@link javax.xml.xpath.XPathConstants#BOOLEAN}</li>
 <li>{@link javax.xml.xpath.XPathConstants#NUMBER}</li>
 </ul>

 <p>When a <code>Boolean</code> return type is requested,
 <code>Boolean.TRUE</code> is returned if one or more nodes were
 selected; otherwise, <code>Boolean.FALSE</code> is returned.</p>

 <p>The <code>String</code> return type is a convenience for retrieving
 the character data from a text node, attribute node, comment node, or
 processing-instruction node. When used on an element node, the value
 of the child text nodes is returned.
 </p>

 <p>The <code>Number</code> return type attempts to coalesce the text
 of a node to a <code>double</code> data type.
 </p>

 <h3>XPath Context</h3>

 <p>XPath location paths may be relative to a particular node in the
 document, known as the <code>context</code>. Consider the following
 XML document:</p>

 <pre>
 &lt;widgets&gt;
 &lt;widget&gt;
 &lt;manufacturer/&gt;
 &lt;dimensions/&gt;
 &lt;/widget&gt;
 &lt;/widgets&gt;
 </pre>

 <p>The <code>&lt;widget&gt;</code> element can be selected with the
 following XPath API code:</p>

 <pre>
 // parse the XML as a W3C Document
 DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
 builderFactory.setNamespaceAware(true);
 DocumentBuilder builder = builderFactory.newDocumentBuilder();
 Document document = builder.parse(new File("/widgets.xml"));

 XPath xpath = XPathFactory.newInstance().newXPath();
 String expression = "/widgets/widget";
 Node widgetNode = (Node) xpath.evaluate(expression, document, XPathConstants.NODE);
 </pre>

 <p>With a reference to the <code>&lt;widget&gt;</code> element, a
 relative XPath expression can now written to select the
 <code>&lt;manufacturer&gt;</code> child element:</p>

 <pre>
 XPath xpath = XPathFactory.newInstance().newXPath();
 <strong>String expression = "manufacturer";</strong>
 Node manufacturerNode = (Node) xpath.evaluate(expression, <strong>widgetNode</strong>, XPathConstants.NODE);
 </pre>

 <ul>
 <li>Author <a href="mailto:Ben@galbraiths.org">Ben Galbraith</a></li>
 <li>Author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a></li>
 <li>Author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a></li>
 <li>See <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a></li>
 <li>Since 1.5</li>
 </ul>
 </body>
 </html>
	<?xml version="1.0" encoding="UTF-8"?>
	<!-- $Id: package.html 570107 2007-08-27 13:30:19Z mrglavas $ -->

	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
	"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<title>javax.xml.xpath</title>
	<meta name="@author" content="mailto:Ben@galbraiths.org" />
	<meta name="@author" content="mailto:Norman.Walsh@Sun.com" />
	<meta name="@author" content="mailto:Jeff.Suttor@Sun.com" />
	<meta name="@version" content="$Revision: 570107 $, $Date: 2007-08-27 06:30:19 -0700 (Mon, 27 Aug 2007) $" />
	<meta name="@see" content="http://www.w3.org/TR/xpath" />
	<meta name="@since" content="1.5" />
	</head>

	<body>

	<p>This package provides an <em>object-model neutral</em> API for the
	evaluation of XPath expressions and access to the evaluation
	environment.
	</p>

	<p>The following XML standards apply:</p>

	<ul>
	<li><a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a></li>
	</ul>

	<hr />

	<h2>XPath Overview</h2>

	<p>The XPath language provides a simple, concise syntax for selecting
	nodes from an XML document. XPath also provides rules for converting a
	node in an XML document object model (DOM) tree to a boolean, double,
	or string value. XPath is a W3C-defined language and an official W3C
	recommendation; the W3C hosts the XML Path Language (XPath) Version
	1.0 specification.
	</p>

	<p>XPath started in life in 1999 as a supplement to the XSLT and
	XPointer languages, but has more recently become popular as a
	stand-alone language, as a single XPath expression can be used to
	replace many lines of DOM API code.
	</p>

	<h3>XPath Expressions</h3>

	<p>An XPath <em>expression</em> is composed of a <em>location
	path</em> and one or more optional <em>predicates</em>. Expressions
	may also include XPath variables.
	</p>

	<p>The following is an example of a simple XPath expression:</p>

	<pre>
	/foo/bar
	</pre>

	<p>This example would select the <code><bar></code> element in
	an XML document such as the following:</p>

	<pre>
	<foo>
	<bar/>
	</foo>
	</pre>

	<p>The expression <code>/foo/bar</code> is an example of a location
	path. While XPath location paths resemble Unix-style file system
	paths, an important distinction is that XPath expressions return
	<em>all</em> nodes that match the expression. Thus, all three
	<code><bar></code> elements in the following document would be
	selected by the <code>/foo/bar</code> expression:</p>

	<pre>
	<foo>
	<bar/>
	<bar/>
	<bar/>
	</foo>
	</pre>

	<p>A special location path operator, <code>//</code>, selects nodes at
	any depth in an XML document. The following example selects all
	<code><bar></code> elements regardless of their location in a
	document:</p>

	<pre>
	//bar
	</pre>

	<p>A wildcard operator, *, causes all element nodes to be selected.
	The following example selects all children elements of a
	<code><foo></code> element:</p>

	<pre>
	/foo/*
	</pre>

	<p>In addition to element nodes, XPath location paths may also address
	attribute nodes, text nodes, comment nodes, and processing instruction
	nodes. The following table gives examples of location paths for each
	of these node types:</p>

	<table border="1">
	<tr>
	<td>Location Path</td>
	<td>Description</td>
	</tr>
	<tr>
	<td>
	<code>/foo/bar/<strong>@id</strong></code>
	</td>
	<td>Selects the attribute <code>id</code> of the <code><bar></code> element
	</td>
	</tr>
	<tr>
	<td><code>/foo/bar/<strong>text()</strong></code>
	</td>
	<td>Selects the text nodes of the <code><bar></code> element. No
	distinction is made between escaped and non-escaped character data.
	</td>
	</tr>
	<tr>
	<td><code>/foo/bar/<strong>comment()</strong></code>
	</td>
	<td>Selects all comment nodes contained in the <code><bar></code> element.
	</td>
	</tr>
	<tr>
	<td><code>/foo/bar/<strong>processing-instruction()</strong></code>
	</td>
	<td>Selects all processing-instruction nodes contained in the
	<code><bar></code> element.
	</td>
	</tr>
	</table>

	<p>Predicates allow for refining the nodes selected by an XPath
	location path. Predicates are of the form
	<code>[<em>expression</em>]</code>. The following example selects all
	<code><foo></code> elements that contain an <code>include</code>
	attribute with the value of <code>true</code>:</p>

	<pre>
	//foo[@include='true']
	</pre>

	<p>Predicates may be appended to each other to further refine an
	expression, such as:</p>

	<pre>
	//foo[@include='true'][@mode='bar']
	</pre>

	<h3>Using the XPath API</h3>

	<p>
	The following example demonstrates using the XPath API to select one
	or more nodes from an XML document:</p>

	<pre>
	XPath xpath = XPathFactory.newInstance().newXPath();
	String expression = "/widgets/widget";
	InputSource inputSource = new InputSource("widgets.xml");
	NodeSet nodes = (NodeSet) xpath.evaluate(expression, inputSource, XPathConstants.NODESET);
	</pre>

	<h3>XPath Expressions and Types</h3>

	<p>While XPath expressions select nodes in the XML document, the XPath
	API allows the selected nodes to be coalesced into one of the
	following other data types:</p>

	<ul>
	<li><code>Boolean</code></li>
	<li><code>Number</code></li>
	<li><code>String</code></li>
	</ul>

	<p>The desired return type is specified by a {@link
	javax.xml.namespace.QName} parameter in method call used to evaluate
	the expression, which is either a call to
	<code>XPathExpression.evaluate(...)</code> or to one of the
	<code>XPath.evaluate(...)</code> convenience methods. The allowed
	QName values are specified as constants in the {@link
	javax.xml.xpath.XPathConstants} class; they are:</p>

	<ul>
	<li>{@link javax.xml.xpath.XPathConstants#NODESET}</li>
	<li>{@link javax.xml.xpath.XPathConstants#NODE}</li>
	<li>{@link javax.xml.xpath.XPathConstants#STRING}</li>
	<li>{@link javax.xml.xpath.XPathConstants#BOOLEAN}</li>
	<li>{@link javax.xml.xpath.XPathConstants#NUMBER}</li>
	</ul>

	<p>When a <code>Boolean</code> return type is requested,
	<code>Boolean.TRUE</code> is returned if one or more nodes were
	selected; otherwise, <code>Boolean.FALSE</code> is returned.</p>

	<p>The <code>String</code> return type is a convenience for retrieving
	the character data from a text node, attribute node, comment node, or
	processing-instruction node. When used on an element node, the value
	of the child text nodes is returned.
	</p>

	<p>The <code>Number</code> return type attempts to coalesce the text
	of a node to a <code>double</code> data type.
	</p>

	<h3>XPath Context</h3>

	<p>XPath location paths may be relative to a particular node in the
	document, known as the <code>context</code>. Consider the following
	XML document:</p>

	<pre>
	<widgets>
	<widget>
	<manufacturer/>
	<dimensions/>
	</widget>
	</widgets>
	</pre>

	<p>The <code><widget></code> element can be selected with the
	following XPath API code:</p>

	<pre>
	// parse the XML as a W3C Document
	DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
	builderFactory.setNamespaceAware(true);
	DocumentBuilder builder = builderFactory.newDocumentBuilder();
	Document document = builder.parse(new File("/widgets.xml"));

	XPath xpath = XPathFactory.newInstance().newXPath();
	String expression = "/widgets/widget";
	Node widgetNode = (Node) xpath.evaluate(expression, document, XPathConstants.NODE);
	</pre>

	<p>With a reference to the <code><widget></code> element, a
	relative XPath expression can now written to select the
	<code><manufacturer></code> child element:</p>

	<pre>
	XPath xpath = XPathFactory.newInstance().newXPath();
	<strong>String expression = "manufacturer";</strong>
	Node manufacturerNode = (Node) xpath.evaluate(expression, <strong>widgetNode</strong>, XPathConstants.NODE);
	</pre>

	<ul>
	<li>Author <a href="mailto:Ben@galbraiths.org">Ben Galbraith</a></li>
	<li>Author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a></li>
	<li>Author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a></li>
	<li>See <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a></li>
	<li>Since 1.5</li>
	</ul>
	</body>
	</html>