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
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
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 final 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 * The class loader is asked for service provider provider-configuration files matching <code>javax.xml.xpath.XPathFactory</code>
125 * in the resource directory META-INF/services.
126 * See the JAR File Specification for file format and parsing rules.
127 * Each potential service provider is required to implement the method:
128 * <pre>
129 * {@link #isObjectModelSupported(String objectModel)}
130 * </pre>
131 * The first service provider found in class loader order that supports the specified object model is returned.
132 * </li>
133 * <li>
134 * Platform default <code>XPathFactory</code> is located in a platform specific way.
135 * There must be a platform default XPathFactory for the W3C DOM, i.e. {@link #DEFAULT_OBJECT_MODEL_URI}.
136 * </li>
137 * </ol>
138 * <p>If everything fails, an <code>XPathFactoryConfigurationException</code> will be thrown.</p>
139 *
140 * <p>Tip for Trouble-shooting:</p>
141 * <p>See {@link java.util.Properties#load(java.io.InputStream)} for exactly how a property file is parsed.
142 * In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it.
143 * For example:</p>
144 * <pre>
145 * http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
146 * </pre>
147 *
148 * @param uri Identifies the underlying object model.
149 * The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI},
150 * <code>http://java.sun.com/jaxp/xpath/dom</code> for the W3C DOM,
151 * the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
152 *
153 * @return Instance of an <code>XPathFactory</code>.
154 *
155 * @throws XPathFactoryConfigurationException If the specified object model is unavailable.
156 * @throws NullPointerException If <code>uri</code> is <code>null</code>.
157 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
158 * or <code>uri.length() == 0</code>.
159 */
160 public static final XPathFactory newInstance(final String uri)
161 throws XPathFactoryConfigurationException {
162
163 if (uri == null) {
164 throw new NullPointerException(
165 "XPathFactory#newInstance(String uri) cannot be called with uri == null"
166 );
167 }
168
169 if (uri.length() == 0) {
170 throw new IllegalArgumentException(
171 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
172 );
173 }
174
175 ClassLoader classLoader = ss.getContextClassLoader();
176
177 if (classLoader == null) {
178 //use the current class loader
179 classLoader = XPathFactory.class.getClassLoader();
180 }
181
182 XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri);
183
184 if (xpathFactory == null) {
185 throw new XPathFactoryConfigurationException(
186 "No XPathFactory implementation found for the object model: "
187 + uri
188 );
189 }
190
191 return xpathFactory;
192 }
193
194 /**
195 * <p>Obtain a new instance of a <code>XPathFactory</code> from a factory class name. <code>XPathFactory</code>
196 * is returned if specified factory class supports the specified object model.
197 * This function is useful when there are multiple providers in the classpath.
198 * It gives more control to the application as it can specify which provider
199 * should be loaded.</p>
200 *
201 *
202 * <h2>Tip for Trouble-shooting</h2>
203 * <p>Setting the <code>jaxp.debug</code> system property will cause
204 * this method to print a lot of debug messages
205 * to <code>System.err</code> about what it is doing and where it is looking at.</p>
206 *
207 * <p> If you have problems try:</p>
208 * <pre>
209 * java -Djaxp.debug=1 YourProgram ....
210 * </pre>
211 *
212 * @param uri Identifies the underlying object model. The specification only defines the URI
213 * {@link #DEFAULT_OBJECT_MODEL_URI},<code>http://java.sun.com/jaxp/xpath/dom</code>
214 * for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce
215 * other URIs for other object models.
216 *
217 * @param factoryClassName fully qualified factory class name that provides implementation of <code>javax.xml.xpath.XPathFactory</code>.
218 *
219 * @param classLoader <code>ClassLoader</code> used to load the factory class. If <code>null</code>
220 * current <code>Thread</code>'s context classLoader is used to load the factory class.
221 *
222 *
223 * @return New instance of a <code>XPathFactory</code>
224 *
225 * @throws XPathFactoryConfigurationException
226 * if <code>factoryClassName</code> is <code>null</code>, or
227 * the factory class cannot be loaded, instantiated
228 * or the factory class does not support the object model specified
229 * in the <code>uri</code> parameter.
230 *
231 * @throws NullPointerException If <code>uri</code> is <code>null</code>.
232 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
233 * or <code>uri.length() == 0</code>.
234 *
235 * @see #newInstance()
236 * @see #newInstance(String uri)
237 *
238 * @since 1.6
239 */
240 public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader)
241 throws XPathFactoryConfigurationException{
242 ClassLoader cl = classLoader;
243
244 if (uri == null) {
245 throw new NullPointerException(
246 "XPathFactory#newInstance(String uri) cannot be called with uri == null"
247 );
248 }
249
250 if (uri.length() == 0) {
251 throw new IllegalArgumentException(
252 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
253 );
254 }
255
256 if (cl == null) {
257 cl = ss.getContextClassLoader();
258 }
259
260 XPathFactory f = new XPathFactoryFinder(cl).createInstance(factoryClassName);
261
262 if (f == null) {
263 throw new XPathFactoryConfigurationException(
264 "No XPathFactory implementation found for the object model: "
265 + uri
266 );
267 }
268 //if this factory supports the given schemalanguage return this factory else thrown exception
269 if(f.isObjectModelSupported(uri)){
270 return f;
271 }else{
272 throw new XPathFactoryConfigurationException("Factory " + factoryClassName + " doesn't support given " + uri + " 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 }