1 /* 2 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package javax.xml.xpath; 27 28 /** 29 * <p>An <code>XPathFactory</code> instance can be used to create 30 * {@link javax.xml.xpath.XPath} objects.</p> 31 * 32 *<p>See {@link #newInstance(String uri)} for lookup mechanism.</p> 33 * 34 * <p>The {@link XPathFactory} class is not thread-safe. In other words, 35 * it is the application's responsibility to ensure that at most 36 * one thread is using a {@link XPathFactory} object at any 37 * given moment. Implementations are encouraged to mark methods 38 * as <code>synchronized</code> to protect themselves from broken clients. 39 * 40 * <p>{@link XPathFactory} is not re-entrant. While one of the 41 * <code>newInstance</code> methods is being invoked, applications 42 * may not attempt to recursively invoke a <code>newInstance</code> method, 43 * even from the same thread. 44 * 45 * @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a> 46 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a> 47 * 48 * @since 1.5 49 */ 50 public abstract class XPathFactory { 51 52 53 /** 54 * <p>The default property name according to the JAXP spec.</p> 55 */ 56 public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory"; 57 58 /** 59 * <p>Default Object Model URI.</p> 60 */ 61 public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom"; 62 63 /** 64 *<p> Take care of restrictions imposed by java security model </p> 65 */ 66 private static SecuritySupport ss = new SecuritySupport() ; 67 68 /** 69 * <p>Protected constructor as {@link #newInstance()} or {@link #newInstance(String uri)} 70 * or {@link #newInstance(String uri, String factoryClassName, ClassLoader classLoader)} 71 * should be used to create a new instance of an <code>XPathFactory</code>.</p> 72 */ 73 protected XPathFactory() { 74 } 75 76 /** 77 * <p>Get a new <code>XPathFactory</code> instance using the default object model, 78 * {@link #DEFAULT_OBJECT_MODEL_URI}, 79 * the W3C DOM.</p> 80 * 81 * <p>This method is functionally equivalent to:</p> 82 * <pre> 83 * newInstance(DEFAULT_OBJECT_MODEL_URI) 84 * </pre> 85 * 86 * <p>Since the implementation for the W3C DOM is always available, this method will never fail.</p> 87 * 88 * @return Instance of an <code>XPathFactory</code>. 89 * 90 * @throws RuntimeException When there is a failure in creating an 91 * <code>XPathFactory</code> for the default object model. 92 */ 93 public static XPathFactory newInstance() { 94 95 try { 96 return newInstance(DEFAULT_OBJECT_MODEL_URI); 97 } catch (XPathFactoryConfigurationException xpathFactoryConfigurationException) { 98 throw new RuntimeException( 99 "XPathFactory#newInstance() failed to create an XPathFactory for the default object model: " 100 + DEFAULT_OBJECT_MODEL_URI 101 + " with the XPathFactoryConfigurationException: " 102 + xpathFactoryConfigurationException.toString() 103 ); 104 } 105 } 106 107 /** 108 * <p>Get a new <code>XPathFactory</code> instance using the specified object model.</p> 109 * 110 * <p>To find a <code>XPathFactory</code> object, 111 * this method looks the following places in the following order where "the class loader" refers to the context class loader:</p> 112 * <ol> 113 * <li> 114 * If the system property {@link #DEFAULT_PROPERTY_NAME} + ":uri" is present, 115 * where uri is the parameter to this method, then its value is read as a class name. 116 * The method will try to create a new instance of this class by using the class loader, 117 * and returns it if it is successfully created. 118 * </li> 119 * <li> 120 * ${java.home}/lib/jaxp.properties is read and the value associated with the key being the system property above is looked for. 121 * If present, the value is processed just like above. 122 * </li> 123 * <li> 124 * Use the service-provider loading facilities, defined by the 125 * {@link java.util.ServiceLoader} class, to attempt to locate and load an 126 * implementation of the service using the {@linkplain 127 * java.util.ServiceLoader#load(java.lang.Class) default loading mechanism}: 128 * the service-provider loading facility will use the {@linkplain 129 * java.lang.Thread#getContextClassLoader() current thread's context class loader} 130 * to attempt to load the service. If the context class 131 * loader is null, the {@linkplain 132 * ClassLoader#getSystemClassLoader() system class loader} will be used. 133 * <br> 134 * Each potential service provider is required to implement the method 135 * {@link #isObjectModelSupported(String objectModel)}. 136 * The first service provider found that supports the specified object 137 * model is returned. 138 * <br> 139 * In case of {@link java.util.ServiceConfigurationError} an 140 * {@link XPathFactoryConfigurationException} will be thrown. 141 * </li> 142 * <li> 143 * Platform default <code>XPathFactory</code> is located in a platform specific way. 144 * There must be a platform default XPathFactory for the W3C DOM, i.e. {@link #DEFAULT_OBJECT_MODEL_URI}. 145 * </li> 146 * </ol> 147 * <p>If everything fails, an <code>XPathFactoryConfigurationException</code> will be thrown.</p> 148 * 149 * <p>Tip for Trouble-shooting:</p> 150 * <p>See {@link java.util.Properties#load(java.io.InputStream)} for exactly how a property file is parsed. 151 * In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it. 152 * For example:</p> 153 * <pre> 154 * http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory 155 * </pre> 156 * 157 * @param uri Identifies the underlying object model. 158 * The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI}, 159 * <code>http://java.sun.com/jaxp/xpath/dom</code> for the W3C DOM, 160 * the org.w3c.dom package, and implementations are free to introduce other URIs for other object models. 161 * 162 * @return Instance of an <code>XPathFactory</code>. 163 * 164 * @throws XPathFactoryConfigurationException If the specified object model 165 * is unavailable, or if there is a configuration error. 166 * @throws NullPointerException If <code>uri</code> is <code>null</code>. 167 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code> 168 * or <code>uri.length() == 0</code>. 169 */ 170 public static XPathFactory newInstance(final String uri) 171 throws XPathFactoryConfigurationException { 172 173 if (uri == null) { 174 throw new NullPointerException( 175 "XPathFactory#newInstance(String uri) cannot be called with uri == null"); 176 } 177 178 if (uri.length() == 0) { 179 throw new IllegalArgumentException( 180 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\""); 181 } 182 183 ClassLoader classLoader = ss.getContextClassLoader(); 184 185 if (classLoader == null) { 186 //use the current class loader 187 classLoader = XPathFactory.class.getClassLoader(); 188 } 189 190 XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri); 191 192 if (xpathFactory == null) { 193 throw new XPathFactoryConfigurationException( 194 "No XPathFactory implementation found for the object model: " 195 + uri); 196 } 197 198 return xpathFactory; 199 } 200 201 /** 202 * <p>Obtain a new instance of a <code>XPathFactory</code> from a factory class name. <code>XPathFactory</code> 203 * is returned if specified factory class supports the specified object model. 204 * This function is useful when there are multiple providers in the classpath. 205 * It gives more control to the application as it can specify which provider 206 * should be loaded.</p> 207 * 208 * 209 * <h2>Tip for Trouble-shooting</h2> 210 * <p>Setting the <code>jaxp.debug</code> system property will cause 211 * this method to print a lot of debug messages 212 * to <code>System.err</code> about what it is doing and where it is looking at.</p> 213 * 214 * <p> If you have problems try:</p> 215 * <pre> 216 * java -Djaxp.debug=1 YourProgram .... 217 * </pre> 218 * 219 * @param uri Identifies the underlying object model. The specification only defines the URI 220 * {@link #DEFAULT_OBJECT_MODEL_URI},<code>http://java.sun.com/jaxp/xpath/dom</code> 221 * for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce 222 * other URIs for other object models. 223 * 224 * @param factoryClassName fully qualified factory class name that provides implementation of <code>javax.xml.xpath.XPathFactory</code>. 225 * 226 * @param classLoader <code>ClassLoader</code> used to load the factory class. If <code>null</code> 227 * current <code>Thread</code>'s context classLoader is used to load the factory class. 228 * 229 * 230 * @return New instance of a <code>XPathFactory</code> 231 * 232 * @throws XPathFactoryConfigurationException 233 * if <code>factoryClassName</code> is <code>null</code>, or 234 * the factory class cannot be loaded, instantiated 235 * or the factory class does not support the object model specified 236 * in the <code>uri</code> parameter. 237 * 238 * @throws NullPointerException If <code>uri</code> is <code>null</code>. 239 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code> 240 * or <code>uri.length() == 0</code>. 241 * 242 * @see #newInstance() 243 * @see #newInstance(String uri) 244 * 245 * @since 1.6 246 */ 247 public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader) 248 throws XPathFactoryConfigurationException{ 249 ClassLoader cl = classLoader; 250 251 if (uri == null) { 252 throw new NullPointerException( 253 "XPathFactory#newInstance(String uri) cannot be called with uri == null"); 254 } 255 256 if (uri.length() == 0) { 257 throw new IllegalArgumentException( 258 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\""); 259 } 260 261 if (cl == null) { 262 cl = ss.getContextClassLoader(); 263 } 264 265 XPathFactory f = new XPathFactoryFinder(cl).createInstance(factoryClassName); 266 267 if (f == null) { 268 throw new XPathFactoryConfigurationException( 269 "No XPathFactory implementation found for the object model: " 270 + uri); 271 } 272 //if this factory supports the given schemalanguage return this factory else thrown exception 273 if (f.isObjectModelSupported(uri)) { 274 return f; 275 } else { 276 throw new XPathFactoryConfigurationException("Factory " 277 + factoryClassName + " doesn't support given " + uri 278 + " object model"); 279 } 280 281 } 282 283 /** 284 * <p>Is specified object model supported by this <code>XPathFactory</code>?</p> 285 * 286 * @param objectModel Specifies the object model which the returned <code>XPathFactory</code> will understand. 287 * 288 * @return <code>true</code> if <code>XPathFactory</code> supports <code>objectModel</code>, else <code>false</code>. 289 * 290 * @throws NullPointerException If <code>objectModel</code> is <code>null</code>. 291 * @throws IllegalArgumentException If <code>objectModel.length() == 0</code>. 292 */ 293 public abstract boolean isObjectModelSupported(String objectModel); 294 295 /** 296 * <p>Set a feature for this <code>XPathFactory</code> and 297 * <code>XPath</code>s created by this factory.</p> 298 * 299 * <p> 300 * Feature names are fully qualified {@link java.net.URI}s. 301 * Implementations may define their own features. 302 * An {@link XPathFactoryConfigurationException} is thrown if this 303 * <code>XPathFactory</code> or the <code>XPath</code>s 304 * it creates cannot support the feature. 305 * It is possible for an <code>XPathFactory</code> to expose a feature value 306 * but be unable to change its state. 307 * </p> 308 * 309 * <p> 310 * All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature. 311 * When the feature is <code>true</code>, any reference to an external function is an error. 312 * Under these conditions, the implementation must not call the {@link XPathFunctionResolver} 313 * and must throw an {@link XPathFunctionException}. 314 * </p> 315 * 316 * @param name Feature name. 317 * @param value Is feature state <code>true</code> or <code>false</code>. 318 * 319 * @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s 320 * it creates cannot support this feature. 321 * @throws NullPointerException if <code>name</code> is <code>null</code>. 322 */ 323 public abstract void setFeature(String name, boolean value) 324 throws XPathFactoryConfigurationException; 325 326 /** 327 * <p>Get the state of the named feature.</p> 328 * 329 * <p> 330 * Feature names are fully qualified {@link java.net.URI}s. 331 * Implementations may define their own features. 332 * An {@link XPathFactoryConfigurationException} is thrown if this 333 * <code>XPathFactory</code> or the <code>XPath</code>s 334 * it creates cannot support the feature. 335 * It is possible for an <code>XPathFactory</code> to expose a feature value 336 * but be unable to change its state. 337 * </p> 338 * 339 * @param name Feature name. 340 * 341 * @return State of the named feature. 342 * 343 * @throws XPathFactoryConfigurationException if this 344 * <code>XPathFactory</code> or the <code>XPath</code>s 345 * it creates cannot support this feature. 346 * @throws NullPointerException if <code>name</code> is <code>null</code>. 347 */ 348 public abstract boolean getFeature(String name) 349 throws XPathFactoryConfigurationException; 350 351 /** 352 * <p>Establish a default variable resolver.</p> 353 * 354 * <p>Any <code>XPath</code> objects constructed from this factory will use 355 * the specified resolver by default.</p> 356 * 357 * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> 358 * is <code>null</code>.</p> 359 * 360 * @param resolver Variable resolver. 361 * 362 * @throws NullPointerException If <code>resolver</code> is 363 * <code>null</code>. 364 */ 365 public abstract void setXPathVariableResolver(XPathVariableResolver resolver); 366 367 /** 368 * <p>Establish a default function resolver.</p> 369 * 370 * <p>Any <code>XPath</code> objects constructed from this factory will 371 * use the specified resolver by default.</p> 372 * 373 * <p>A <code>NullPointerException</code> is thrown if 374 * <code>resolver</code> is <code>null</code>.</p> 375 * 376 * @param resolver XPath function resolver. 377 * 378 * @throws NullPointerException If <code>resolver</code> is 379 * <code>null</code>. 380 */ 381 public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver); 382 383 /** 384 * <p>Return a new <code>XPath</code> using the underlying object 385 * model determined when the <code>XPathFactory</code> was instantiated.</p> 386 * 387 * @return New instance of an <code>XPath</code>. 388 */ 389 public abstract XPath newXPath(); 390 }