1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> 2 <html> 3 <head> 4 <!-- 5 Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved. 6 DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 8 This code is free software; you can redistribute it and/or modify it 9 under the terms of the GNU General Public License version 2 only, as 10 published by the Free Software Foundation. Oracle designates this 11 particular file as subject to the "Classpath" exception as provided 12 by Oracle in the LICENSE file that accompanied this code. 13 14 This code is distributed in the hope that it will be useful, but WITHOUT 15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 version 2 for more details (a copy is included in the LICENSE file that 18 accompanied this code). 19 20 You should have received a copy of the GNU General Public License version 21 2 along with this work; if not, write to the Free Software Foundation, 22 Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 23 24 Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 25 or visit www.oracle.com if you need additional information or have any 26 questions. 27 --> 28 </head> 29 <body bgcolor="white"> 30 31 This package provides an <em>object-model neutral</em> API for the 32 evaluation of XPath expressions and access to the evaluation 33 environment. 34 35 <p> 36 The XPath API supports <a href="http://www.w3.org/TR/xpath"> 37 XML Path Language (XPath) Version 1.0</a> 38 39 <hr /> 40 41 <ul> 42 <li><a href='#XPath.Overview'>1. XPath Overview</a></li> 43 <li><a href='#XPath.Expressions'>2. XPath Expressions</a></li> 44 <li><a href='#XPath.Datatypes'>3. XPath Data Types</a> 45 <ul> 46 <li><a href='#XPath.Datatypes.QName'>3.1 QName Types</a> 47 <li><a href='#XPath.Datatypes.Class'>3.2 Class Types</a> 48 <li><a href='#XPath.Datatypes.Enum'>3.3 Enum Types</a> 49 </ul> 50 </li> 51 <li><a href='#XPath.Context'>4. XPath Context</a></li> 52 <li><a href='#XPath.Use'>5. Using the XPath API</a></li> 53 </ul> 54 <p> 55 <a name="XPath.Overview"></a> 56 <h3>1. XPath Overview</h3> 57 58 <p>The XPath language provides a simple, concise syntax for selecting 59 nodes from an XML document. XPath also provides rules for converting a 60 node in an XML document object model (DOM) tree to a boolean, double, 61 or string value. XPath is a W3C-defined language and an official W3C 62 recommendation; the W3C hosts the XML Path Language (XPath) Version 63 1.0 specification. 64 </p> 65 66 <p>XPath started in life in 1999 as a supplement to the XSLT and 67 XPointer languages, but has more recently become popular as a 68 stand-alone language, as a single XPath expression can be used to 69 replace many lines of DOM API code. 70 </p> 71 72 <a name="XPath.Expressions"></a> 73 <h3>2. XPath Expressions</h3> 74 75 <p>An XPath <em>expression</em> is composed of a <em>location 76 path</em> and one or more optional <em>predicates</em>. Expressions 77 may also include XPath variables. 78 </p> 79 80 <p>The following is an example of a simple XPath expression:</p> 81 82 <blockquote> 83 <pre> 84 /foo/bar 85 </pre> 86 </blockquote> 87 88 <p>This example would select the <code><bar></code> element in 89 an XML document such as the following:</p> 90 91 <blockquote> 92 <pre> 122 <pre> 123 //bar 124 </pre> 125 </blockquote> 126 127 <p>A wildcard operator, *, causes all element nodes to be selected. 128 The following example selects all children elements of a 129 <code><foo></code> element: 130 131 <blockquote> 132 <pre> 133 /foo/* 134 </pre> 135 </blockquote> 136 137 <p>In addition to element nodes, XPath location paths may also address 138 attribute nodes, text nodes, comment nodes, and processing instruction 139 nodes. The following table gives examples of location paths for each 140 of these node types:</p> 141 142 <table border="1"> 143 <tr> 144 <td>Location Path</td> 145 <td>Description</td> 146 </tr> 147 <tr> 148 <td> 149 <code>/foo/bar/<strong>@id</strong></code> 150 </td> 151 <td>Selects the attribute <code>id</code> of the <code><bar></code> element 152 </td> 153 </tr> 154 <tr> 155 <td><code>/foo/bar/<strong>text()</strong></code> 156 </td> 157 <td>Selects the text nodes of the <code><bar></code> element. No 158 distinction is made between escaped and non-escaped character data. 159 </td> 160 </tr> 161 <tr> 162 <td><code>/foo/bar/<strong>comment()</strong></code> 163 </td> 164 <td>Selects all comment nodes contained in the <code><bar></code> element. 165 </td> 166 </tr> 167 <tr> 168 <td><code>/foo/bar/<strong>processing-instruction()</strong></code> 169 </td> 170 <td>Selects all processing-instruction nodes contained in the 171 <code><bar></code> element. 172 </td> 173 </tr> 174 </table> 175 176 <p>Predicates allow for refining the nodes selected by an XPath 177 location path. Predicates are of the form 178 <code>[<em>expression</em>]</code>. The following example selects all 179 <code><foo></code> elements that contain an <code>include</code> 180 attribute with the value of <code>true</code>:</p> 181 182 <blockquote> 183 <pre> 184 //foo[@include='true'] 185 </pre> 186 </blockquote> 187 188 <p>Predicates may be appended to each other to further refine an 189 expression, such as:</p> 190 191 <blockquote> 192 <pre> 193 //foo[@include='true'][@mode='bar'] 194 </pre> 195 </blockquote> 196 197 <a name="XPath.Datatypes"></a> 198 <h3>3. XPath Data Types</h3> 199 200 <p>While XPath expressions select nodes in the XML document, the XPath 201 API allows the selected nodes to be coalesced into one of the 202 following data types:</p> 203 204 <ul> 205 <li><code>Boolean</code></li> 206 <li><code>Number</code></li> 207 <li><code>String</code></li> 208 </ul> 209 210 <a name="XPath.Datatypes.QName"></a> 211 <h3>3.1 QName types</h3> 212 The XPath API defines the following {@link javax.xml.namespace.QName} types to 213 represent return types of an XPath evaluation: 214 <ul> 215 <li>{@link javax.xml.xpath.XPathConstants#NODESET}</li> 216 <li>{@link javax.xml.xpath.XPathConstants#NODE}</li> 217 <li>{@link javax.xml.xpath.XPathConstants#STRING}</li> 218 <li>{@link javax.xml.xpath.XPathConstants#BOOLEAN}</li> 219 <li>{@link javax.xml.xpath.XPathConstants#NUMBER}</li> 220 </ul> 221 222 <p>The return type is specified by a {@link javax.xml.namespace.QName} parameter 223 in method call used to evaluate the expression, which is either a call to 224 <code>XPathExpression.evalute(...)</code> or <code>XPath.evaluate(...)</code> 225 methods. 226 227 <p>When a <code>Boolean</code> return type is requested, 228 <code>Boolean.TRUE</code> is returned if one or more nodes were 229 selected; otherwise, <code>Boolean.FALSE</code> is returned. 230 231 <p>The <code>String</code> return type is a convenience for retrieving 232 the character data from a text node, attribute node, comment node, or 233 processing-instruction node. When used on an element node, the value 234 of the child text nodes is returned. 235 236 <p>The <code>Number</code> return type attempts to coalesce the text 237 of a node to a <code>double</code> data type. 238 239 <a name="XPath.Datatypes.Class"></a> 240 <h3>3.2 Class types</h3> 241 In addition to the QName types, the XPath API supports the use of Class types 242 through the <code>XPathExpression.evaluteExpression(...)</code> or 243 <code>XPath.evaluateExpression(...)</code> methods. 244 245 The XPath data types are mapped to Class types as follows: 246 <ul> 247 <li><code>Boolean</code> -- <code>Boolean.class</code></li> 248 <li><code>Number</code> -- <code>Number.class</code></li> 249 <li><code>String</code> -- <code>String.class</code></li> 250 <li><code>Nodeset</code> -- <code>XPathNodes.class</code></li> 251 <li><code>Node</code> -- <code>Node.class</code></li> 252 </ul> 253 254 <p> 255 Of the subtypes of Number, only Double, Integer and Long are supported. 256 257 <a name="XPath.Datatypes.Enum"></a> 258 <h3>3.3 Enum types</h3> 259 Enum types are defined in {@link javax.xml.xpath.XPathEvaluationResult.XPathResultType} 260 that provide mappings between the QName and Class types above. The result of 261 evaluating an expression using the <code>XPathExpression.evaluteExpression(...)</code> 262 or <code>XPath.evaluateExpression(...)</code> methods will be of one of these types. 263 264 <a name="XPath.Context"></a> 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 <widgets> 288 <widget> 289 <manufacturer/> 290 <dimensions/> 291 </widget> 292 </widgets> 293 </pre> 294 </blockquote> 295 296 <p> 297 The <code><widget></code> element can be selected with the following process: 298 299 <blockquote> 300 <pre> 301 // parse the XML as a W3C Document | 1 <!doctype html> 2 <html> 3 <head> 4 <!-- 5 Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved. 6 DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 8 This code is free software; you can redistribute it and/or modify it 9 under the terms of the GNU General Public License version 2 only, as 10 published by the Free Software Foundation. Oracle designates this 11 particular file as subject to the "Classpath" exception as provided 12 by Oracle in the LICENSE file that accompanied this code. 13 14 This code is distributed in the hope that it will be useful, but WITHOUT 15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 version 2 for more details (a copy is included in the LICENSE file that 18 accompanied this code). 19 20 You should have received a copy of the GNU General Public License version 21 2 along with this work; if not, write to the Free Software Foundation, 22 Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 23 24 Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 25 or visit www.oracle.com if you need additional information or have any 26 questions. 27 --> 28 </head> 29 <body> 30 31 This package provides an <em>object-model neutral</em> API for the 32 evaluation of XPath expressions and access to the evaluation 33 environment. 34 35 <p> 36 The XPath API supports <a href="http://www.w3.org/TR/xpath"> 37 XML Path Language (XPath) Version 1.0</a> 38 39 <hr> 40 41 <ul> 42 <li><a href='#XPath.Overview'>1. XPath Overview</a></li> 43 <li><a href='#XPath.Expressions'>2. XPath Expressions</a></li> 44 <li><a href='#XPath.Datatypes'>3. XPath Data Types</a> 45 <ul> 46 <li><a href='#XPath.Datatypes.QName'>3.1 QName Types</a> 47 <li><a href='#XPath.Datatypes.Class'>3.2 Class Types</a> 48 <li><a href='#XPath.Datatypes.Enum'>3.3 Enum Types</a> 49 </ul> 50 </li> 51 <li><a href='#XPath.Context'>4. XPath Context</a></li> 52 <li><a href='#XPath.Use'>5. Using the XPath API</a></li> 53 </ul> 54 <p> 55 <a id="XPath.Overview"></a> 56 <h3>1. XPath Overview</h3> 57 58 <p>The XPath language provides a simple, concise syntax for selecting 59 nodes from an XML document. XPath also provides rules for converting a 60 node in an XML document object model (DOM) tree to a boolean, double, 61 or string value. XPath is a W3C-defined language and an official W3C 62 recommendation; the W3C hosts the XML Path Language (XPath) Version 63 1.0 specification. 64 </p> 65 66 <p>XPath started in life in 1999 as a supplement to the XSLT and 67 XPointer languages, but has more recently become popular as a 68 stand-alone language, as a single XPath expression can be used to 69 replace many lines of DOM API code. 70 </p> 71 72 <a id="XPath.Expressions"></a> 73 <h3>2. XPath Expressions</h3> 74 75 <p>An XPath <em>expression</em> is composed of a <em>location 76 path</em> and one or more optional <em>predicates</em>. Expressions 77 may also include XPath variables. 78 </p> 79 80 <p>The following is an example of a simple XPath expression:</p> 81 82 <blockquote> 83 <pre> 84 /foo/bar 85 </pre> 86 </blockquote> 87 88 <p>This example would select the <code><bar></code> element in 89 an XML document such as the following:</p> 90 91 <blockquote> 92 <pre> 122 <pre> 123 //bar 124 </pre> 125 </blockquote> 126 127 <p>A wildcard operator, *, causes all element nodes to be selected. 128 The following example selects all children elements of a 129 <code><foo></code> element: 130 131 <blockquote> 132 <pre> 133 /foo/* 134 </pre> 135 </blockquote> 136 137 <p>In addition to element nodes, XPath location paths may also address 138 attribute nodes, text nodes, comment nodes, and processing instruction 139 nodes. The following table gives examples of location paths for each 140 of these node types:</p> 141 142 <table class="striped"> 143 <caption>Examples of Location Path</caption> 144 <thead> 145 <tr> 146 <th>Location Path</th> 147 <th>Description</th> 148 </tr> 149 </thead> 150 <tbody> 151 <tr> 152 <td> 153 <code>/foo/bar/<strong>@id</strong></code> 154 </td> 155 <td>Selects the attribute <code>id</code> of the <code><bar></code> element 156 </td> 157 </tr> 158 <tr> 159 <td><code>/foo/bar/<strong>text()</strong></code> 160 </td> 161 <td>Selects the text nodes of the <code><bar></code> element. No 162 distinction is made between escaped and non-escaped character data. 163 </td> 164 </tr> 165 <tr> 166 <td><code>/foo/bar/<strong>comment()</strong></code> 167 </td> 168 <td>Selects all comment nodes contained in the <code><bar></code> element. 169 </td> 170 </tr> 171 <tr> 172 <td><code>/foo/bar/<strong>processing-instruction()</strong></code> 173 </td> 174 <td>Selects all processing-instruction nodes contained in the 175 <code><bar></code> element. 176 </td> 177 </tr> 178 </tbody> 179 </table> 180 181 <p>Predicates allow for refining the nodes selected by an XPath 182 location path. Predicates are of the form 183 <code>[<em>expression</em>]</code>. The following example selects all 184 <code><foo></code> elements that contain an <code>include</code> 185 attribute with the value of <code>true</code>:</p> 186 187 <blockquote> 188 <pre> 189 //foo[@include='true'] 190 </pre> 191 </blockquote> 192 193 <p>Predicates may be appended to each other to further refine an 194 expression, such as:</p> 195 196 <blockquote> 197 <pre> 198 //foo[@include='true'][@mode='bar'] 199 </pre> 200 </blockquote> 201 202 <a id="XPath.Datatypes"></a> 203 <h3>3. XPath Data Types</h3> 204 205 <p>While XPath expressions select nodes in the XML document, the XPath 206 API allows the selected nodes to be coalesced into one of the 207 following data types:</p> 208 209 <ul> 210 <li><code>Boolean</code></li> 211 <li><code>Number</code></li> 212 <li><code>String</code></li> 213 </ul> 214 215 <a id="XPath.Datatypes.QName"></a> 216 <h3>3.1 QName types</h3> 217 The XPath API defines the following {@link javax.xml.namespace.QName} types to 218 represent return types of an XPath evaluation: 219 <ul> 220 <li>{@link javax.xml.xpath.XPathConstants#NODESET}</li> 221 <li>{@link javax.xml.xpath.XPathConstants#NODE}</li> 222 <li>{@link javax.xml.xpath.XPathConstants#STRING}</li> 223 <li>{@link javax.xml.xpath.XPathConstants#BOOLEAN}</li> 224 <li>{@link javax.xml.xpath.XPathConstants#NUMBER}</li> 225 </ul> 226 227 <p>The return type is specified by a {@link javax.xml.namespace.QName} parameter 228 in method call used to evaluate the expression, which is either a call to 229 <code>XPathExpression.evalute(...)</code> or <code>XPath.evaluate(...)</code> 230 methods. 231 232 <p>When a <code>Boolean</code> return type is requested, 233 <code>Boolean.TRUE</code> is returned if one or more nodes were 234 selected; otherwise, <code>Boolean.FALSE</code> is returned. 235 236 <p>The <code>String</code> return type is a convenience for retrieving 237 the character data from a text node, attribute node, comment node, or 238 processing-instruction node. When used on an element node, the value 239 of the child text nodes is returned. 240 241 <p>The <code>Number</code> return type attempts to coalesce the text 242 of a node to a <code>double</code> data type. 243 244 <a id="XPath.Datatypes.Class"></a> 245 <h3>3.2 Class types</h3> 246 In addition to the QName types, the XPath API supports the use of Class types 247 through the <code>XPathExpression.evaluteExpression(...)</code> or 248 <code>XPath.evaluateExpression(...)</code> methods. 249 250 The XPath data types are mapped to Class types as follows: 251 <ul> 252 <li><code>Boolean</code> -- <code>Boolean.class</code></li> 253 <li><code>Number</code> -- <code>Number.class</code></li> 254 <li><code>String</code> -- <code>String.class</code></li> 255 <li><code>Nodeset</code> -- <code>XPathNodes.class</code></li> 256 <li><code>Node</code> -- <code>Node.class</code></li> 257 </ul> 258 259 <p> 260 Of the subtypes of Number, only Double, Integer and Long are supported. 261 262 <a id="XPath.Datatypes.Enum"></a> 263 <h3>3.3 Enum types</h3> 264 Enum types are defined in {@link javax.xml.xpath.XPathEvaluationResult.XPathResultType} 265 that provide mappings between the QName and Class types above. The result of 266 evaluating an expression using the <code>XPathExpression.evaluteExpression(...)</code> 267 or <code>XPath.evaluateExpression(...)</code> methods will be of one of these types. 268 269 <a id="XPath.Context"></a> 270 <h3>4. XPath Context</h3> 271 272 <p>XPath location paths may be relative to a particular node in the 273 document, known as the <code>context</code>. A context consists of: 274 <ul> 275 <li>a node (the context node)</li> 276 <li>a pair of non-zero positive integers (the context position and the context size)</li> 277 <li>a set of variable bindings</li> 278 <li>a function library</li> 279 <li>the set of namespace declarations in scope for the expression</li> 280 </ul> 281 282 <p> 283 It is an XML document tree represented as a hierarchy of nodes, a 284 {@link org.w3c.dom.Node} for example, in the JDK implementation. 285 286 <a id="XPath.Use"></a> 287 <h3>5. Using the XPath API</h3> 288 289 Consider the following XML document: 290 <blockquote> 291 <pre> 292 <widgets> 293 <widget> 294 <manufacturer/> 295 <dimensions/> 296 </widget> 297 </widgets> 298 </pre> 299 </blockquote> 300 301 <p> 302 The <code><widget></code> element can be selected with the following process: 303 304 <blockquote> 305 <pre> 306 // parse the XML as a W3C Document |