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-</head>
-<body>
-
-This package provides an <em>object-model neutral</em> API for the
-evaluation of XPath expressions and access to the evaluation
-environment.
-
-<p>
-The XPath API supports <a href="http://www.w3.org/TR/xpath">
- XML Path Language (XPath) Version 1.0</a>
-
-<hr>
-
-<ul>
- <li><a href='#XPath.Overview'>1. XPath Overview</a></li>
- <li><a href='#XPath.Expressions'>2. XPath Expressions</a></li>
- <li><a href='#XPath.Datatypes'>3. XPath Data Types</a>
- <ul>
- <li><a href='#XPath.Datatypes.QName'>3.1 QName Types</a>
- <li><a href='#XPath.Datatypes.Class'>3.2 Class Types</a>
- <li><a href='#XPath.Datatypes.Enum'>3.3 Enum Types</a>
- </ul>
- </li>
- <li><a href='#XPath.Context'>4. XPath Context</a></li>
- <li><a href='#XPath.Use'>5. Using the XPath API</a></li>
-</ul>
-<p>
-<a id="XPath.Overview"></a>
-<h3>1. XPath Overview</h3>
-
-<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>
-
-<a id="XPath.Expressions"></a>
-<h3>2. 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>
-
-<blockquote>
-<pre>
-/foo/bar
-</pre>
-</blockquote>
-
-<p>This example would select the <code><bar></code> element in
-an XML document such as the following:</p>
-
-<blockquote>
-<pre>
-<foo>
- <bar/>
-</foo>
-</pre>
-</blockquote>
-
-<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>
-
-<blockquote>
-<pre>
-<foo>
- <bar/>
- <bar/>
- <bar/>
-</foo>
-</pre>
-</blockquote>
-
-<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>
-
-<blockquote>
-<pre>
-//bar
-</pre>
-</blockquote>
-
-<p>A wildcard operator, *, causes all element nodes to be selected.
-The following example selects all children elements of a
-<code><foo></code> element:
-
-<blockquote>
-<pre>
-/foo/*
-</pre>
-</blockquote>
-
-<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 class="striped">
-<caption>Examples of Location Path</caption>
-<thead>
-<tr>
-<th>Location Path</th>
-<th>Description</th>
-</tr>
-</thead>
-<tbody>
-<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>
-</tbody>
-</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>
-
-<blockquote>
-<pre>
-//foo[@include='true']
-</pre>
-</blockquote>
-
-<p>Predicates may be appended to each other to further refine an
-expression, such as:</p>
-
-<blockquote>
-<pre>
-//foo[@include='true'][@mode='bar']
-</pre>
-</blockquote>
-
-<a id="XPath.Datatypes"></a>
-<h3>3. XPath Data 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 data types:</p>
-
-<ul>
-<li><code>Boolean</code></li>
-<li><code>Number</code></li>
-<li><code>String</code></li>
-</ul>
-
-<a id="XPath.Datatypes.QName"></a>
-<h3>3.1 QName types</h3>
-The XPath API defines the following {@link javax.xml.namespace.QName} types to
-represent return types of an XPath evaluation:
-<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>The 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.evalute(...)</code> or <code>XPath.evaluate(...)</code>
-methods.
-
-<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>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>The <code>Number</code> return type attempts to coalesce the text
-of a node to a <code>double</code> data type.
-
-<a id="XPath.Datatypes.Class"></a>
-<h3>3.2 Class types</h3>
-In addition to the QName types, the XPath API supports the use of Class types
-through the <code>XPathExpression.evaluteExpression(...)</code> or
-<code>XPath.evaluateExpression(...)</code> methods.
-
-The XPath data types are mapped to Class types as follows:
-<ul>
-<li><code>Boolean</code> -- <code>Boolean.class</code></li>
-<li><code>Number</code> -- <code>Number.class</code></li>
-<li><code>String</code> -- <code>String.class</code></li>
-<li><code>Nodeset</code> -- <code>XPathNodes.class</code></li>
-<li><code>Node</code> -- <code>Node.class</code></li>
-</ul>
-
-<p>
-Of the subtypes of Number, only Double, Integer and Long are supported.
-
-<a id="XPath.Datatypes.Enum"></a>
-<h3>3.3 Enum types</h3>
-Enum types are defined in {@link javax.xml.xpath.XPathEvaluationResult.XPathResultType}
-that provide mappings between the QName and Class types above. The result of
-evaluating an expression using the <code>XPathExpression.evaluteExpression(...)</code>
-or <code>XPath.evaluateExpression(...)</code> methods will be of one of these types.
-
-<a id="XPath.Context"></a>
-<h3>4. XPath Context</h3>
-
-<p>XPath location paths may be relative to a particular node in the
-document, known as the <code>context</code>. A context consists of:
-<ul>
- <li>a node (the context node)</li>
- <li>a pair of non-zero positive integers (the context position and the context size)</li>
- <li>a set of variable bindings</li>
- <li>a function library</li>
- <li>the set of namespace declarations in scope for the expression</li>
-</ul>
-
-<p>
-It is an XML document tree represented as a hierarchy of nodes, a
-{@link org.w3c.dom.Node} for example, in the JDK implementation.
-
-<a id="XPath.Use"></a>
-<h3>5. Using the XPath API</h3>
-
-Consider the following XML document:
-<blockquote>
-<pre>
-<widgets>
-<widget>
-<manufacturer/>
-<dimensions/>
-</widget>
-</widgets>
-</pre>
-</blockquote>
-
-<p>
-The <code><widget></code> element can be selected with the following process:
-
-<blockquote>
-<pre>
-// parse the XML as a W3C Document
-DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
-Document document = builder.parse(new File("/widgets.xml"));
-
-//Get an XPath object and evaluate the expression
-XPath xpath = XPathFactory.newInstance().newXPath();
-String expression = "/widgets/widget";
-Node widgetNode = (Node) xpath.evaluate(expression, document, XPathConstants.NODE);
-
-//or using the evaluateExpression method
-Node widgetNode = xpath.evaluateExpression(expression, document, Node.class);
-</pre>
-</blockquote>
-
-<p>With a reference to the <code><widget></code> element, a
-relative XPath expression can be written to select the
-<code><manufacturer></code> child element:</p>
-
-<blockquote>
-<pre>
-XPath xpath = XPathFactory.newInstance().newXPath();
-<strong>String expression = "manufacturer";</strong>
-Node manufacturerNode = (Node) xpath.evaluate(expression, <strong>widgetNode</strong>, XPathConstants.NODE);
-
-//or using the evaluateExpression method
-Node manufacturerNode = xpath.evaluateExpression(expression, <strong>widgetNode</strong>, Node.class);
-</pre>
-</blockquote>
-
-<p>
-In the above example, the XML file is read into a DOM Document before being passed
-to the XPath API. The following code demonstrates the use of InputSource to
-leave it to the XPath implementation to process it:
-
-<blockquote>
-<pre>
-XPath xpath = XPathFactory.newInstance().newXPath();
-String expression = "/widgets/widget";
-InputSource inputSource = new InputSource("widgets.xml");
-NodeList nodes = (NodeList) xpath.evaluate(expression, inputSource, XPathConstants.NODESET);
-
-//or using the evaluateExpression method
-XPathNodes nodes = xpath.evaluate(expression, inputSource, XPathNodes.class);
-</pre>
-</blockquote>
-
-<p>
-In the above cases, the type of the expected results are known. In case where
-the result type is unknown or any type, the {@link javax.xml.xpath.XPathEvaluationResult}
-may be used to determine the return type. The following code demonstrates the usage:
-<blockquote>
-<pre>
-XPathEvaluationResult<?> result = xpath.evaluateExpression(expression, document);
-switch (result.type()) {
- case NODESET:
- XPathNodes nodes = (XPathNodes)result.value();
- ...
- break;
-}
-</pre>
-</blockquote>
-
-<p>
-The XPath 1.0 Number data type is defined as a double. However, the XPath
-specification also provides functions that returns Integer type. To facilitate
-such operations, the XPath API allows Integer and Long to be used in
-{@code evaluateExpression} method such as the following code:
-<blockquote>
-<pre>
-int count = xpath.evaluate("count(/widgets/widget)", document, Integer.class);
-</pre>
-</blockquote>
-
-@since 1.5
-
-</body>
-</html>