| /* |
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| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
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| * |
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| |
| /** |
| * |
| * 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> |
| * <h2>1. 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> |
| * 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. |
| * |
| * |
| * <a id="XPath.Expressions"></a> |
| * <h2>2. XPath Expressions</h2> |
| * |
| * <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> |
| * The following is an example of a simple XPath expression: |
| * |
| * <blockquote> |
| * <pre> |
| * /foo/bar |
| * </pre> |
| * </blockquote> |
| * |
| * <p> |
| * This example would select the <code><bar></code> element in |
| * an XML document such as the following: |
| * |
| * <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: |
| * |
| * <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: |
| * |
| * <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: |
| * |
| * <table class="striped"> |
| * <caption>Examples of Location Path</caption> |
| * <thead> |
| * <tr> |
| * <th scope="col">Location Path</th> |
| * <th scope="col">Description</th> |
| * </tr> |
| * </thead> |
| * <tbody> |
| * <tr> |
| * <th scope="row"> |
| * <code>/foo/bar/<strong>@id</strong></code> |
| * </th> |
| * <td> |
| * Selects the attribute <code>id</code> of the <code><bar></code> element |
| * </td> |
| * </tr> |
| * <tr> |
| * <th scope="row"><code>/foo/bar/<strong>text()</strong></code> |
| * </th> |
| * <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> |
| * <th scope="row"><code>/foo/bar/<strong>comment()</strong></code> |
| * </th> |
| * <td> |
| * Selects all comment nodes contained in the <code><bar></code> element. |
| * </td> |
| * </tr> |
| * <tr> |
| * <th scope="row"><code>/foo/bar/<strong>processing-instruction()</strong></code> |
| * </th> |
| * <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>: |
| * |
| * <blockquote> |
| * <pre> |
| * //foo[@include='true'] |
| * </pre> |
| * </blockquote> |
| * |
| * <p> |
| * Predicates may be appended to each other to further refine an |
| * expression, such as: |
| * |
| * <blockquote> |
| * <pre> |
| * //foo[@include='true'][@mode='bar'] |
| * </pre> |
| * </blockquote> |
| * |
| * <a id="XPath.Datatypes"></a> |
| * <h2>3. XPath Data Types</h2> |
| * |
| * <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: |
| * |
| * <ul> |
| * <li><code>Boolean</code></li> |
| * <li><code>Number</code></li> |
| * <li><code>String</code></li> |
| * </ul> |
| * |
| * <a id="XPath.Datatypes.QName"></a> |
| * <h2>3.1 QName types</h2> |
| * 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> |
| * <h2>3.2 Class types</h2> |
| * 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> |
| * <h2>3.3 Enum types</h2> |
| * 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> |
| * <h2>4. XPath Context</h2> |
| * |
| * <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> |
| * <h2>5. Using the XPath API</h2> |
| * |
| * 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: |
| * |
| * <blockquote> |
| * <pre> |
| * XPath xpath = XPathFactory.newInstance().newXPath(); |
| * String expression = <b>"manufacturer";</b> |
| * Node manufacturerNode = (Node) xpath.evaluate(expression, <b>widgetNode</b>, XPathConstants.NODE); |
| * |
| * //or using the evaluateExpression method |
| * Node manufacturerNode = xpath.evaluateExpression(expression, <b>widgetNode</b>, 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 |
| * |
| */ |
| |
| package javax.xml.xpath; |
