1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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7 * published by the Free Software Foundation. Oracle designates this
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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 *
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24 */
25
26 package javax.xml.xpath;
27
28 import com.sun.org.apache.xpath.internal.jaxp.XPathFactoryImpl;
29 import jdk.xml.internal.SecuritySupport;
30
31 /**
32 * <p>An {@code XPathFactory} instance can be used to create
33 * {@link javax.xml.xpath.XPath} objects.</p>
34 *
35 *<p>See {@link #newInstance(String uri)} for lookup mechanism.</p>
36 *
37 * <p>The {@link XPathFactory} class is not thread-safe. In other words,
38 * it is the application's responsibility to ensure that at most
39 * one thread is using a {@link XPathFactory} object at any
40 * given moment. Implementations are encouraged to mark methods
41 * as <code>synchronized</code> to protect themselves from broken clients.
42 *
43 * <p>{@link XPathFactory} is not re-entrant. While one of the
44 * <code>newInstance</code> methods is being invoked, applications
45 * may not attempt to recursively invoke a <code>newInstance</code> method,
46 * even from the same thread.
47 *
48 * @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
49 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
50 *
51 * @since 1.5
52 */
53 public abstract class XPathFactory {
54
55
56 /**
57 * <p>The default property name according to the JAXP spec.</p>
58 */
59 public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory";
60
61 /**
62 * <p>Default Object Model URI.</p>
63 */
64 public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom";
65
66 /**
67 * <p>Protected constructor as {@link #newInstance()} or {@link #newInstance(String uri)}
68 * or {@link #newInstance(String uri, String factoryClassName, ClassLoader classLoader)}
69 * should be used to create a new instance of an {@code XPathFactory}.</p>
70 */
71 protected XPathFactory() {
72 }
73
74 /**
75 * Creates a new instance of the {@code XPathFactory} builtin
76 * system-default implementation.
77 *
78 * @implSpec The {@code XPathFactory} builtin
79 * system-default implementation is only required to support the
80 * {@link #DEFAULT_OBJECT_MODEL_URI default object model}, the
81 * {@linkplain org.w3c.dom W3C DOM}, but may support additional
82 * object models.
83 *
84 * @return A new instance of the {@code XPathFactory} builtin
85 * system-default implementation.
86 *
87 * @since 9
88 */
89 public static XPathFactory newDefaultInstance() {
90 return XPathFactoryImpl.newXPathFactoryNoServiceLoader();
91 }
92
93 /**
94 * <p>Get a new {@code XPathFactory} instance using the default object model,
95 * {@link #DEFAULT_OBJECT_MODEL_URI},
96 * the W3C DOM.</p>
97 *
98 * <p>This method is functionally equivalent to:</p>
99 * <pre>
100 * newInstance(DEFAULT_OBJECT_MODEL_URI)
101 * </pre>
102 *
103 * <p>Since the implementation for the W3C DOM is always available, this method will never fail.</p>
104 *
105 * @return Instance of an {@code XPathFactory}.
106 *
107 * @throws RuntimeException When there is a failure in creating an
108 * {@code XPathFactory} for the default object model.
109 */
110 public static XPathFactory newInstance() {
111
112 try {
113 return newInstance(DEFAULT_OBJECT_MODEL_URI);
114 } catch (XPathFactoryConfigurationException e) {
115 throw new RuntimeException(
116 "XPathFactory#newInstance() failed to create an XPathFactory for the default object model: "
117 + DEFAULT_OBJECT_MODEL_URI
118 + " with the XPathFactoryConfigurationException: "
119 + e.getMessage(), e
120 );
121 }
122 }
123
124 /**
125 * <p>Get a new {@code XPathFactory} instance using the specified object model.</p>
126 *
127 * <p>To find a {@code XPathFactory} object,
128 * this method looks the following places in the following order where "the class loader" refers to the context class loader:</p>
129 * <ol>
130 * <li>
131 * <p>
132 * If the system property {@link #DEFAULT_PROPERTY_NAME} + ":uri" is present,
133 * where uri is the parameter to this method, then its value is read as a class name.
134 * The method will try to create a new instance of this class by using the class loader,
135 * and returns it if it is successfully created.
136 * </li>
137 * <li>
138 * <p>
139 * Use the configuration file "jaxp.properties". The file is in standard
140 * {@link java.util.Properties} format and typically located in the
141 * conf directory of the Java installation. It contains the fully qualified
142 * name of the implementation class with the key being the system property
143 * defined above.
144 * <p>
145 * The jaxp.properties file is read only once by the JAXP implementation
146 * and its values are then cached for future use. If the file does not exist
147 * when the first attempt is made to read from it, no further attempts are
148 * made to check for its existence. It is not possible to change the value
149 * of any property in jaxp.properties after it has been read for the first time.
150 * </li>
151 * <li>
152 * <p>
153 * Use the service-provider loading facility, defined by the
154 * {@link java.util.ServiceLoader} class, to attempt to locate and load an
155 * implementation of the service using the {@linkplain
156 * java.util.ServiceLoader#load(java.lang.Class) default loading mechanism}:
157 * the service-provider loading facility will use the {@linkplain
158 * java.lang.Thread#getContextClassLoader() current thread's context class loader}
159 * to attempt to load the service. If the context class
160 * loader is null, the {@linkplain
161 * ClassLoader#getSystemClassLoader() system class loader} will be used.
162 * <br>
163 * Each potential service provider is required to implement the method
164 * {@link #isObjectModelSupported(String objectModel)}.
165 * The first service provider found that supports the specified object
166 * model is returned.
167 * <br>
168 * In case of {@link java.util.ServiceConfigurationError} an
169 * {@link XPathFactoryConfigurationException} will be thrown.
170 * </li>
171 * <li>
172 * <p>
173 * Platform default {@code XPathFactory} is located in a platform
174 * specific way.
175 * There must be a {@linkplain #newDefaultInstance() platform default}
176 * {@code XPathFactory} for the W3C DOM, i.e.
177 * {@link #DEFAULT_OBJECT_MODEL_URI}.
178 * </li>
179 * </ol>
180 * <p>If everything fails, an {@code XPathFactoryConfigurationException} will be thrown.
181 *
182 * <p>Tip for Trouble-shooting:
183 * <p>See {@link java.util.Properties#load(java.io.InputStream)} for exactly how a property file is parsed.
184 * In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it.
185 * For example:
186 * <pre>
187 * http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
188 * </pre>
189 *
190 * @param uri Identifies the underlying object model.
191 * The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI},
192 * <code>http://java.sun.com/jaxp/xpath/dom</code> for the W3C DOM,
193 * the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
194 *
195 * @return Instance of an {@code XPathFactory}.
196 *
197 * @throws XPathFactoryConfigurationException If the specified object model
198 * is unavailable, or if there is a configuration error.
199 * @throws NullPointerException If <code>uri</code> is <code>null</code>.
200 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
201 * or <code>uri.length() == 0</code>.
202 */
203 public static XPathFactory newInstance(final String uri)
204 throws XPathFactoryConfigurationException {
205
206 if (uri == null) {
207 throw new NullPointerException(
208 "XPathFactory#newInstance(String uri) cannot be called with uri == null");
209 }
210
211 if (uri.length() == 0) {
212 throw new IllegalArgumentException(
213 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\"");
214 }
215
216 ClassLoader classLoader = SecuritySupport.getContextClassLoader();
217
218 if (classLoader == null) {
219 //use the current class loader
220 classLoader = XPathFactory.class.getClassLoader();
221 }
222
223 XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri);
224
225 if (xpathFactory == null) {
226 throw new XPathFactoryConfigurationException(
227 "No XPathFactory implementation found for the object model: "
228 + uri);
229 }
230
231 return xpathFactory;
232 }
233
234 /**
235 * <p>Obtain a new instance of a {@code XPathFactory} from a factory class name. {@code XPathFactory}
236 * is returned if specified factory class supports the specified object model.
237 * This function is useful when there are multiple providers in the classpath.
238 * It gives more control to the application as it can specify which provider
239 * should be loaded.</p>
240 *
241 *
242 * <h2>Tip for Trouble-shooting</h2>
243 * <p>Setting the <code>jaxp.debug</code> system property will cause
244 * this method to print a lot of debug messages
245 * to <code>System.err</code> about what it is doing and where it is looking at.</p>
246 *
247 * <p> If you have problems try:</p>
248 * <pre>
249 * java -Djaxp.debug=1 YourProgram ....
250 * </pre>
251 *
252 * @param uri Identifies the underlying object model. The specification only defines the URI
253 * {@link #DEFAULT_OBJECT_MODEL_URI},<code>http://java.sun.com/jaxp/xpath/dom</code>
254 * for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce
255 * other URIs for other object models.
256 *
257 * @param factoryClassName fully qualified factory class name that provides implementation of <code>javax.xml.xpath.XPathFactory</code>.
258 *
259 * @param classLoader <code>ClassLoader</code> used to load the factory class. If <code>null</code>
260 * current <code>Thread</code>'s context classLoader is used to load the factory class.
261 *
262 *
263 * @return New instance of a {@code XPathFactory}
264 *
265 * @throws XPathFactoryConfigurationException
266 * if <code>factoryClassName</code> is <code>null</code>, or
267 * the factory class cannot be loaded, instantiated
268 * or the factory class does not support the object model specified
269 * in the <code>uri</code> parameter.
270 *
271 * @throws NullPointerException If <code>uri</code> is <code>null</code>.
272 * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
273 * or <code>uri.length() == 0</code>.
274 *
275 * @see #newInstance()
276 * @see #newInstance(String uri)
277 *
278 * @since 1.6
279 */
280 public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader)
281 throws XPathFactoryConfigurationException{
282 ClassLoader cl = classLoader;
283
284 if (uri == null) {
285 throw new NullPointerException(
286 "XPathFactory#newInstance(String uri) cannot be called with uri == null");
287 }
288
289 if (uri.length() == 0) {
290 throw new IllegalArgumentException(
291 "XPathFactory#newInstance(String uri) cannot be called with uri == \"\"");
292 }
293
294 if (cl == null) {
295 cl = SecuritySupport.getContextClassLoader();
296 }
297
298 XPathFactory f = new XPathFactoryFinder(cl).createInstance(factoryClassName);
299
300 if (f == null) {
301 throw new XPathFactoryConfigurationException(
302 "No XPathFactory implementation found for the object model: "
303 + uri);
304 }
305 //if this factory supports the given schemalanguage return this factory else thrown exception
306 if (f.isObjectModelSupported(uri)) {
307 return f;
308 } else {
309 throw new XPathFactoryConfigurationException("Factory "
310 + factoryClassName + " doesn't support given " + uri
311 + " object model");
312 }
313
314 }
315
316 /**
317 * <p>Is specified object model supported by this {@code XPathFactory}?</p>
318 *
319 * @param objectModel Specifies the object model which the returned {@code XPathFactory} will understand.
320 *
321 * @return <code>true</code> if {@code XPathFactory} supports <code>objectModel</code>, else <code>false</code>.
322 *
323 * @throws NullPointerException If <code>objectModel</code> is <code>null</code>.
324 * @throws IllegalArgumentException If <code>objectModel.length() == 0</code>.
325 */
326 public abstract boolean isObjectModelSupported(String objectModel);
327
328 /**
329 * <p>Set a feature for this {@code XPathFactory} and
330 * <code>XPath</code>s created by this factory.</p>
331 *
332 * <p>
333 * Feature names are fully qualified {@link java.net.URI}s.
334 * Implementations may define their own features.
335 * An {@link XPathFactoryConfigurationException} is thrown if this
336 * {@code XPathFactory} or the <code>XPath</code>s
337 * it creates cannot support the feature.
338 * It is possible for an {@code XPathFactory} to expose a feature value
339 * but be unable to change its state.
340 * </p>
341 *
342 * <p>
343 * All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature.
344 * When the feature is <code>true</code>, any reference to an external function is an error.
345 * Under these conditions, the implementation must not call the {@link XPathFunctionResolver}
346 * and must throw an {@link XPathFunctionException}.
347 * </p>
348 *
349 * @param name Feature name.
350 * @param value Is feature state <code>true</code> or <code>false</code>.
351 *
352 * @throws XPathFactoryConfigurationException if this {@code XPathFactory} or the <code>XPath</code>s
353 * it creates cannot support this feature.
354 * @throws NullPointerException if <code>name</code> is <code>null</code>.
355 */
356 public abstract void setFeature(String name, boolean value)
357 throws XPathFactoryConfigurationException;
358
359 /**
360 * <p>Get the state of the named feature.</p>
361 *
362 * <p>
363 * Feature names are fully qualified {@link java.net.URI}s.
364 * Implementations may define their own features.
365 * An {@link XPathFactoryConfigurationException} is thrown if this
366 * {@code XPathFactory} or the <code>XPath</code>s
367 * it creates cannot support the feature.
368 * It is possible for an {@code XPathFactory} to expose a feature value
369 * but be unable to change its state.
370 * </p>
371 *
372 * @param name Feature name.
373 *
374 * @return State of the named feature.
375 *
376 * @throws XPathFactoryConfigurationException if this
377 * {@code XPathFactory} or the <code>XPath</code>s
378 * it creates cannot support this feature.
379 * @throws NullPointerException if <code>name</code> is <code>null</code>.
380 */
381 public abstract boolean getFeature(String name)
382 throws XPathFactoryConfigurationException;
383
384 /**
385 * <p>Establish a default variable resolver.</p>
386 *
387 * <p>Any <code>XPath</code> objects constructed from this factory will use
388 * the specified resolver by default.</p>
389 *
390 * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code>
391 * is <code>null</code>.</p>
392 *
393 * @param resolver Variable resolver.
394 *
395 * @throws NullPointerException If <code>resolver</code> is
396 * <code>null</code>.
397 */
398 public abstract void setXPathVariableResolver(XPathVariableResolver resolver);
399
400 /**
401 * <p>Establish a default function resolver.</p>
402 *
403 * <p>Any <code>XPath</code> objects constructed from this factory will
404 * use the specified resolver by default.</p>
405 *
406 * <p>A <code>NullPointerException</code> is thrown if
407 * <code>resolver</code> is <code>null</code>.</p>
408 *
409 * @param resolver XPath function resolver.
410 *
411 * @throws NullPointerException If <code>resolver</code> is
412 * <code>null</code>.
413 */
414 public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver);
415
416 /**
417 * <p>Return a new <code>XPath</code> using the underlying object
418 * model determined when the {@code XPathFactory} was instantiated.</p>
419 *
420 * @return New instance of an <code>XPath</code>.
421 */
422 public abstract XPath newXPath();
423 }