1 /*
2 * Copyright (c) 2003, 2006, 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
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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
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20 *
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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.
127 * <br>
128 * Each potential service provider is required to implement the method
129 * {@link #isObjectModelSupported(String objectModel)}.
130 * The first service provider found that supports the specified object
131 * model is returned.
132 * <br>
133 * In case of {@link java.util.ServiceConfigurationError} an
134 * {@link XPathFactoryConfigurationException} will be thrown.
135 * </li>
136 * <li>
137 * Platform default <code>XPathFactory</code> is located in a platform specific way.
138 * There must be a platform default XPathFactory for the W3C DOM, i.e. {@link #DEFAULT_OBJECT_MODEL_URI}.
139 * </li>
140 * </ol>
141 * <p>If everything fails, an <code>XPathFactoryConfigurationException</code> will be thrown.</p>
142 *
143 * <p>Tip for Trouble-shooting:</p>
144 * <p>See {@link java.util.Properties#load(java.io.InputStream)} for exactly how a property file is parsed.
145 * In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it.
146 * For example:</p>
147 * <pre>
148 * http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
149 * </pre>
150 *
151 * @param uri Identifies the underlying object model.
152 * The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI},
153 * <code>http://java.sun.com/jaxp/xpath/dom</code> for the W3C DOM,
154 * the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
155 *
156 * @return Instance of an <code>XPathFactory</code>.
157 *
158 * @throws XPathFactoryConfigurationException If the specified object model
159 * is unavailable, or if there is a configuration error.
160 * @throws NullPointerException If <code>uri</code> is <code>null</code>.
161 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
162 * or <code>uri.length() == 0</code>.
163 */
164 public static XPathFactory newInstance(final String uri)
165 throws XPathFactoryConfigurationException {
166
167 if (uri == null) {
168 throw new NullPointerException(
169 "XPathFactory#newInstance(String uri) cannot be called with uri == null");
170 }
171
172 if (uri.length() == 0) {
173 throw new IllegalArgumentException(
174 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\"");
175 }
176
177 ClassLoader classLoader = ss.getContextClassLoader();
178
179 if (classLoader == null) {
180 //use the current class loader
181 classLoader = XPathFactory.class.getClassLoader();
182 }
183
184 XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri);
185
186 if (xpathFactory == null) {
187 throw new XPathFactoryConfigurationException(
188 "No XPathFactory implementation found for the object model: "
189 + uri);
190 }
191
192 return xpathFactory;
193 }
194
195 /**
196 * <p>Obtain a new instance of a <code>XPathFactory</code> from a factory class name. <code>XPathFactory</code>
197 * is returned if specified factory class supports the specified object model.
198 * This function is useful when there are multiple providers in the classpath.
199 * It gives more control to the application as it can specify which provider
200 * should be loaded.</p>
201 *
202 *
203 * <h2>Tip for Trouble-shooting</h2>
204 * <p>Setting the <code>jaxp.debug</code> system property will cause
205 * this method to print a lot of debug messages
206 * to <code>System.err</code> about what it is doing and where it is looking at.</p>
207 *
208 * <p> If you have problems try:</p>
209 * <pre>
210 * java -Djaxp.debug=1 YourProgram ....
211 * </pre>
212 *
213 * @param uri Identifies the underlying object model. The specification only defines the URI
214 * {@link #DEFAULT_OBJECT_MODEL_URI},<code>http://java.sun.com/jaxp/xpath/dom</code>
215 * for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce
216 * other URIs for other object models.
217 *
218 * @param factoryClassName fully qualified factory class name that provides implementation of <code>javax.xml.xpath.XPathFactory</code>.
219 *
220 * @param classLoader <code>ClassLoader</code> used to load the factory class. If <code>null</code>
221 * current <code>Thread</code>'s context classLoader is used to load the factory class.
222 *
223 *
224 * @return New instance of a <code>XPathFactory</code>
225 *
226 * @throws XPathFactoryConfigurationException
227 * if <code>factoryClassName</code> is <code>null</code>, or
228 * the factory class cannot be loaded, instantiated
229 * or the factory class does not support the object model specified
230 * in the <code>uri</code> parameter.
231 *
232 * @throws NullPointerException If <code>uri</code> is <code>null</code>.
233 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
234 * or <code>uri.length() == 0</code>.
235 *
236 * @see #newInstance()
237 * @see #newInstance(String uri)
238 *
239 * @since 1.6
240 */
241 public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader)
242 throws XPathFactoryConfigurationException{
243 ClassLoader cl = classLoader;
244
245 if (uri == null) {
246 throw new NullPointerException(
247 "XPathFactory#newInstance(String uri) cannot be called with uri == null");
248 }
249
250 if (uri.length() == 0) {
251 throw new IllegalArgumentException(
252 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\"");
253 }
254
255 if (cl == null) {
256 cl = ss.getContextClassLoader();
257 }
258
259 XPathFactory f = new XPathFactoryFinder(cl).createInstance(factoryClassName);
260
261 if (f == null) {
262 throw new XPathFactoryConfigurationException(
263 "No XPathFactory implementation found for the object model: "
264 + uri);
265 }
266 //if this factory supports the given schemalanguage return this factory else thrown exception
267 if (f.isObjectModelSupported(uri)) {
268 return f;
269 } else {
270 throw new XPathFactoryConfigurationException("Factory "
271 + factoryClassName + " doesn't support given " + uri
272 + " object model");
273 }
274
275 }
276
277 /**
278 * <p>Is specified object model supported by this <code>XPathFactory</code>?</p>
279 *
280 * @param objectModel Specifies the object model which the returned <code>XPathFactory</code> will understand.
281 *
282 * @return <code>true</code> if <code>XPathFactory</code> supports <code>objectModel</code>, else <code>false</code>.
283 *
284 * @throws NullPointerException If <code>objectModel</code> is <code>null</code>.
285 * @throws IllegalArgumentException If <code>objectModel.length() == 0</code>.
286 */
287 public abstract boolean isObjectModelSupported(String objectModel);
288
289 /**
290 * <p>Set a feature for this <code>XPathFactory</code> and
291 * <code>XPath</code>s created by this factory.</p>
292 *
293 * <p>
294 * Feature names are fully qualified {@link java.net.URI}s.
295 * Implementations may define their own features.
296 * An {@link XPathFactoryConfigurationException} is thrown if this
297 * <code>XPathFactory</code> or the <code>XPath</code>s
298 * it creates cannot support the feature.
299 * It is possible for an <code>XPathFactory</code> to expose a feature value
300 * but be unable to change its state.
301 * </p>
302 *
303 * <p>
304 * All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature.
305 * When the feature is <code>true</code>, any reference to an external function is an error.
306 * Under these conditions, the implementation must not call the {@link XPathFunctionResolver}
307 * and must throw an {@link XPathFunctionException}.
308 * </p>
309 *
310 * @param name Feature name.
311 * @param value Is feature state <code>true</code> or <code>false</code>.
312 *
313 * @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s
314 * it creates cannot support this feature.
315 * @throws NullPointerException if <code>name</code> is <code>null</code>.
316 */
317 public abstract void setFeature(String name, boolean value)
318 throws XPathFactoryConfigurationException;
319
320 /**
321 * <p>Get the state of the named feature.</p>
322 *
323 * <p>
324 * Feature names are fully qualified {@link java.net.URI}s.
325 * Implementations may define their own features.
326 * An {@link XPathFactoryConfigurationException} is thrown if this
327 * <code>XPathFactory</code> or the <code>XPath</code>s
328 * it creates cannot support the feature.
329 * It is possible for an <code>XPathFactory</code> to expose a feature value
330 * but be unable to change its state.
331 * </p>
332 *
333 * @param name Feature name.
334 *
335 * @return State of the named feature.
336 *
337 * @throws XPathFactoryConfigurationException if this
338 * <code>XPathFactory</code> or the <code>XPath</code>s
339 * it creates cannot support this feature.
340 * @throws NullPointerException if <code>name</code> is <code>null</code>.
341 */
342 public abstract boolean getFeature(String name)
343 throws XPathFactoryConfigurationException;
344
345 /**
346 * <p>Establish a default variable resolver.</p>
347 *
348 * <p>Any <code>XPath</code> objects constructed from this factory will use
349 * the specified resolver by default.</p>
350 *
351 * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code>
352 * is <code>null</code>.</p>
353 *
354 * @param resolver Variable resolver.
355 *
356 * @throws NullPointerException If <code>resolver</code> is
357 * <code>null</code>.
358 */
359 public abstract void setXPathVariableResolver(XPathVariableResolver resolver);
360
361 /**
362 * <p>Establish a default function resolver.</p>
363 *
364 * <p>Any <code>XPath</code> objects constructed from this factory will
365 * use the specified resolver by default.</p>
366 *
367 * <p>A <code>NullPointerException</code> is thrown if
368 * <code>resolver</code> is <code>null</code>.</p>
369 *
370 * @param resolver XPath function resolver.
371 *
372 * @throws NullPointerException If <code>resolver</code> is
373 * <code>null</code>.
374 */
375 public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver);
376
377 /**
378 * <p>Return a new <code>XPath</code> using the underlying object
379 * model determined when the <code>XPathFactory</code> was instantiated.</p>
380 *
381 * @return New instance of an <code>XPath</code>.
382 */
383 public abstract XPath newXPath();
384 }