/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // $Id: XPathFactory.java 888889 2009-12-09 17:43:18Z mrglavas $ 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.

* * @author Norman Walsh * @author Jeff Suttor * @version $Revision: 888889 $, $Date: 2009-12-09 09:43:18 -0800 (Wed, 09 Dec 2009) $ * @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"; /** *

Protected constructor as {@link #newInstance()}, {@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. */ public static final 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. * The class loader is asked for service provider provider-configuration files matching javax.xml.xpath.XPathFactory * in the resource directory META-INF/services. * See the JAR File Specification for file format and parsing rules. * Each potential service provider is required to implement the method: * 
        *       {@link #isObjectModelSupported(String objectModel)}
    *
    * The first service provider found in class loader order that supports the specified object model is returned. *
    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. * @throws NullPointerException If uri is null. * @throws IllegalArgumentException If uri.length() == 0. */ public static final XPathFactory newInstance(final String uri) throws XPathFactoryConfigurationException { if (uri == null) { throw new NullPointerException("uri == null"); } if (uri.length() == 0) { throw new IllegalArgumentException( "XPathFactory#newInstance(String uri) cannot be called with uri == \"\"" ); } ClassLoader classLoader = Thread.currentThread().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; } /** * @return Instance of an XPathFactory. * * @throws XPathFactoryConfigurationException If the specified object model is unavailable. * @throws NullPointerException If uri is null. * @throws IllegalArgumentException If uri.length() == 0. */ public static XPathFactory newInstance(String uri, String factoryClassName, ClassLoader classLoader) throws XPathFactoryConfigurationException { if (uri == null) { throw new NullPointerException("uri == null"); } if (uri.length() == 0) { throw new IllegalArgumentException( "XPathFactory#newInstance(String uri) cannot be called with uri == \"\"" ); } if (factoryClassName == null) { throw new XPathFactoryConfigurationException("factoryClassName cannot be null."); } if (classLoader == null) { classLoader = Thread.currentThread().getContextClassLoader(); } XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).createInstance(factoryClassName); if (xpathFactory == null || !xpathFactory.isObjectModelSupported(uri)) { throw new XPathFactoryConfigurationException( "No XPathFactory implementation found for the object model: " + uri ); } return xpathFactory; } /** *

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(); }