/* * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.xml.xpath; /** *

An XPathFactory instance can be used to create * {@link javax.xml.xpath.XPath} objects.

* *

See {@link #newInstance(String uri)} for lookup mechanism.

* *

The {@link XPathFactory} class is not thread-safe. In other words, * it is the application's responsibility to ensure that at most * one thread is using a {@link XPathFactory} object at any * given moment. Implementations are encouraged to mark methods * as synchronized to protect themselves from broken clients. * *

{@link XPathFactory} is not re-entrant. While one of the * newInstance methods is being invoked, applications * may not attempt to recursively invoke a newInstance method, * even from the same thread. * * @author Norman Walsh * @author Jeff Suttor * * @since 1.5 */ public abstract class XPathFactory { /** *

The default property name according to the JAXP spec.

*/ public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory"; /** *

Default Object Model URI.

*/ public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom"; /** *

Take care of restrictions imposed by java security model

*/ private static SecuritySupport ss = new SecuritySupport() ; /** *

Protected constructor as {@link #newInstance()} or {@link #newInstance(String uri)} * or {@link #newInstance(String uri, String factoryClassName, ClassLoader classLoader)} * should be used to create a new instance of an XPathFactory.

*/ protected XPathFactory() { } /** *

Get a new XPathFactory instance using the default object model, * {@link #DEFAULT_OBJECT_MODEL_URI}, * the W3C DOM.

* *

This method is functionally equivalent to:

* 
     *   newInstance(DEFAULT_OBJECT_MODEL_URI)
     *
* *

Since the implementation for the W3C DOM is always available, this method will never fail.

* * @return Instance of an XPathFactory. * * @throws RuntimeException When there is a failure in creating an * XPathFactory for the default object model. */ public static XPathFactory newInstance() { try { return newInstance(DEFAULT_OBJECT_MODEL_URI); } catch (XPathFactoryConfigurationException xpathFactoryConfigurationException) { throw new RuntimeException( "XPathFactory#newInstance() failed to create an XPathFactory for the default object model: " + DEFAULT_OBJECT_MODEL_URI + " with the XPathFactoryConfigurationException: " + xpathFactoryConfigurationException.toString() ); } } /** *

Get a new XPathFactory instance using the specified object model.

* *

To find a XPathFactory object, * this method looks the following places in the following order where "the class loader" refers to the context class loader:

*
    *
  1. * If the system property {@link #DEFAULT_PROPERTY_NAME} + ":uri" is present, * where uri is the parameter to this method, then its value is read as a class name. * The method will try to create a new instance of this class by using the class loader, * and returns it if it is successfully created. *
    2. *
  2. * ${java.home}/lib/jaxp.properties is read and the value associated with the key being the system property above is looked for. * If present, the value is processed just like above. *
    3. *
  3. * Use the service-provider loading facilities, defined by the * {@link java.util.ServiceLoader} class, to attempt to locate and load an * implementation of the service using the {@linkplain * java.util.ServiceLoader#load(java.lang.Class) default loading mechanism}: * the service-provider loading facility will use the {@linkplain * java.lang.Thread#getContextClassLoader() current thread's context class loader} * to attempt to load the service. If the context class * loader is null, the {@linkplain * ClassLoader#getSystemClassLoader() system class loader} will be used. *
    * Each potential service provider is required to implement the method * {@link #isObjectModelSupported(String objectModel)}. * The first service provider found that supports the specified object * model is returned. *
    * In case of {@link java.util.ServiceConfigurationError} an * {@link XPathFactoryConfigurationException} will be thrown. *
    4. *
  4. * Platform default XPathFactory is located in a platform specific way. * There must be a platform default XPathFactory for the W3C DOM, i.e. {@link #DEFAULT_OBJECT_MODEL_URI}. *
    5. *
*

If everything fails, an XPathFactoryConfigurationException will be thrown.

* *

Tip for Trouble-shooting:

*

See {@link java.util.Properties#load(java.io.InputStream)} for exactly how a property file is parsed. * In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it. * For example:

* 
    *   http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
    *
* * @param uri Identifies the underlying object model. * The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI}, * http://java.sun.com/jaxp/xpath/dom for the W3C DOM, * the org.w3c.dom package, and implementations are free to introduce other URIs for other object models. * * @return Instance of an XPathFactory. * * @throws XPathFactoryConfigurationException If the specified object model * is unavailable, or if there is a configuration error. * @throws NullPointerException If uri is null. * @throws IllegalArgumentException If uri is null * or uri.length() == 0. */ public static XPathFactory newInstance(final String uri) throws XPathFactoryConfigurationException { if (uri == null) { throw new NullPointerException( "XPathFactory#newInstance(String uri) cannot be called with uri == null"); } if (uri.length() == 0) { throw new IllegalArgumentException( "XPathFactory#newInstance(String uri) cannot be called with uri == \"\""); } ClassLoader classLoader = ss.getContextClassLoader(); if (classLoader == null) { //use the current class loader classLoader = XPathFactory.class.getClassLoader(); } XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri); if (xpathFactory == null) { throw new XPathFactoryConfigurationException( "No XPathFactory implementation found for the object model: " + uri); } return xpathFactory; } /** *

Obtain a new instance of a XPathFactory from a factory class name. XPathFactory * is returned if specified factory class supports the specified object model. * This function is useful when there are multiple providers in the classpath. * It gives more control to the application as it can specify which provider * should be loaded.

* * *

Tip for Trouble-shooting

*

Setting the jaxp.debug system property will cause * this method to print a lot of debug messages * to System.err about what it is doing and where it is looking at.

* *

If you have problems try:

* 
     * java -Djaxp.debug=1 YourProgram ....
     *
* * @param uri Identifies the underlying object model. The specification only defines the URI * {@link #DEFAULT_OBJECT_MODEL_URI},http://java.sun.com/jaxp/xpath/dom * for the W3C DOM, the org.w3c.dom package, and implementations are free to introduce * other URIs for other object models. * * @param factoryClassName fully qualified factory class name that provides implementation of javax.xml.xpath.XPathFactory. * * @param classLoader ClassLoader used to load the factory class. If null * current Thread's context classLoader is used to load the factory class. * * * @return New instance of a XPathFactory * * @throws XPathFactoryConfigurationException * if factoryClassName is null, or * the factory class cannot be loaded, instantiated * or the factory class does not support the object model specified * in the uri parameter. * * @throws NullPointerException If uri is null. * @throws IllegalArgumentException If uri is null * or uri.length() == 0. * * @see #newInstance() * @see #newInstance(String uri) * * @since 1.6 */ public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader) throws XPathFactoryConfigurationException{ ClassLoader cl = classLoader; if (uri == null) { throw new NullPointerException( "XPathFactory#newInstance(String uri) cannot be called with uri == null"); } if (uri.length() == 0) { throw new IllegalArgumentException( "XPathFactory#newInstance(String uri) cannot be called with uri == \"\""); } if (cl == null) { cl = ss.getContextClassLoader(); } XPathFactory f = new XPathFactoryFinder(cl).createInstance(factoryClassName); if (f == null) { throw new XPathFactoryConfigurationException( "No XPathFactory implementation found for the object model: " + uri); } //if this factory supports the given schemalanguage return this factory else thrown exception if (f.isObjectModelSupported(uri)) { return f; } else { throw new XPathFactoryConfigurationException("Factory " + factoryClassName + " doesn't support given " + uri + " object model"); } } /** *

Is specified object model supported by this XPathFactory?

* * @param objectModel Specifies the object model which the returned XPathFactory will understand. * * @return true if XPathFactory supports objectModel, else false. * * @throws NullPointerException If objectModel is null. * @throws IllegalArgumentException If objectModel.length() == 0. */ public abstract boolean isObjectModelSupported(String objectModel); /** *

Set a feature for this XPathFactory and * XPaths created by this factory.

* *

* Feature names are fully qualified {@link java.net.URI}s. * Implementations may define their own features. * An {@link XPathFactoryConfigurationException} is thrown if this * XPathFactory or the XPaths * it creates cannot support the feature. * It is possible for an XPathFactory to expose a feature value * but be unable to change its state. *

* *

* All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature. * When the feature is true, any reference to an external function is an error. * Under these conditions, the implementation must not call the {@link XPathFunctionResolver} * and must throw an {@link XPathFunctionException}. *

* * @param name Feature name. * @param value Is feature state true or false. * * @throws XPathFactoryConfigurationException if this XPathFactory or the XPaths * it creates cannot support this feature. * @throws NullPointerException if name is null. */ public abstract void setFeature(String name, boolean value) throws XPathFactoryConfigurationException; /** *

Get the state of the named feature.

* *

* Feature names are fully qualified {@link java.net.URI}s. * Implementations may define their own features. * An {@link XPathFactoryConfigurationException} is thrown if this * XPathFactory or the XPaths * it creates cannot support the feature. * It is possible for an XPathFactory to expose a feature value * but be unable to change its state. *

* * @param name Feature name. * * @return State of the named feature. * * @throws XPathFactoryConfigurationException if this * XPathFactory or the XPaths * it creates cannot support this feature. * @throws NullPointerException if name is null. */ public abstract boolean getFeature(String name) throws XPathFactoryConfigurationException; /** *

Establish a default variable resolver.

* *

Any XPath objects constructed from this factory will use * the specified resolver by default.

* *

A NullPointerException is thrown if resolver * is null.

* * @param resolver Variable resolver. * * @throws NullPointerException If resolver is * null. */ public abstract void setXPathVariableResolver(XPathVariableResolver resolver); /** *

Establish a default function resolver.

* *

Any XPath objects constructed from this factory will * use the specified resolver by default.

* *

A NullPointerException is thrown if * resolver is null.

* * @param resolver XPath function resolver. * * @throws NullPointerException If resolver is * null. */ public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver); /** *

Return a new XPath using the underlying object * model determined when the XPathFactory was instantiated.

* * @return New instance of an XPath. */ public abstract XPath newXPath(); }