289 lines
12 KiB
Java
289 lines
12 KiB
Java
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/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// $Id: XPathFactory.java 888889 2009-12-09 17:43:18Z mrglavas $
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package javax.xml.xpath;
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/**
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* <p>An <code>XPathFactory</code> instance can be used to create
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* {@link javax.xml.xpath.XPath} objects.</p>
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*
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*<p>See {@link #newInstance(String uri)} for lookup mechanism.</p>
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*
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* @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
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* @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
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* @version $Revision: 888889 $, $Date: 2009-12-09 09:43:18 -0800 (Wed, 09 Dec 2009) $
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* @since 1.5
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*/
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public abstract class XPathFactory {
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/**
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* <p>The default property name according to the JAXP spec.</p>
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*/
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public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory";
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/**
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* <p>Default Object Model URI.</p>
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*/
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public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom";
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/**
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* <p>Protected constructor as {@link #newInstance()}, {@link #newInstance(String uri)}
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* or {@link #newInstance(String uri, String factoryClassName, ClassLoader classLoader)}
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* should be used to create a new instance of an <code>XPathFactory</code>.</p>
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*/
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protected XPathFactory() {
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}
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/**
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* <p>Get a new <code>XPathFactory</code> instance using the default object model,
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* {@link #DEFAULT_OBJECT_MODEL_URI},
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* the W3C DOM.</p>
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*
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* <p>This method is functionally equivalent to:</p>
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* <pre>
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* newInstance(DEFAULT_OBJECT_MODEL_URI)
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* </pre>
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*
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* <p>Since the implementation for the W3C DOM is always available, this method will never fail.</p>
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*
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* @return Instance of an <code>XPathFactory</code>.
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*/
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public static final XPathFactory newInstance() {
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try {
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return newInstance(DEFAULT_OBJECT_MODEL_URI);
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}
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catch (XPathFactoryConfigurationException xpathFactoryConfigurationException) {
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throw new RuntimeException(
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"XPathFactory#newInstance() failed to create an XPathFactory for the default object model: "
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+ DEFAULT_OBJECT_MODEL_URI
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+ " with the XPathFactoryConfigurationException: "
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+ xpathFactoryConfigurationException.toString()
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);
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}
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}
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/**
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* <p>Get a new <code>XPathFactory</code> instance using the specified object model.</p>
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*
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* <p>To find a <code>XPathFactory</code> object,
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* this method looks the following places in the following order where "the class loader" refers to the context class loader:</p>
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* <ol>
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* <li>
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* If the system property {@link #DEFAULT_PROPERTY_NAME} + ":uri" is present,
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* where uri is the parameter to this method, then its value is read as a class name.
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* The method will try to create a new instance of this class by using the class loader,
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* and returns it if it is successfully created.
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* </li>
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* <li>
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* ${java.home}/lib/jaxp.properties is read and the value associated with the key being the system property above is looked for.
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* If present, the value is processed just like above.
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* </li>
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* <li>
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* The class loader is asked for service provider provider-configuration files matching <code>javax.xml.xpath.XPathFactory</code>
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* in the resource directory META-INF/services.
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* See the JAR File Specification for file format and parsing rules.
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* Each potential service provider is required to implement the method:
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* <pre>
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* {@link #isObjectModelSupported(String objectModel)}
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* </pre>
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* The first service provider found in class loader order that supports the specified object model is returned.
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* </li>
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* <li>
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* Platform default <code>XPathFactory</code> is located in a platform specific way.
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* There must be a platform default XPathFactory for the W3C DOM, i.e. {@link #DEFAULT_OBJECT_MODEL_URI}.
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* </li>
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* </ol>
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* <p>If everything fails, an <code>XPathFactoryConfigurationException</code> will be thrown.</p>
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*
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* <p>Tip for Trouble-shooting:</p>
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* <p>See {@link java.util.Properties#load(java.io.InputStream)} for exactly how a property file is parsed.
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* In particular, colons ':' need to be escaped in a property file, so make sure the URIs are properly escaped in it.
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* For example:</p>
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* <pre>
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* http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
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* </pre>
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*
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* @param uri Identifies the underlying object model.
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* The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI},
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* <code>http://java.sun.com/jaxp/xpath/dom</code> for the W3C DOM,
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* the org.w3c.dom package, and implementations are free to introduce other URIs for other object models.
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*
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* @return Instance of an <code>XPathFactory</code>.
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*
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* @throws XPathFactoryConfigurationException If the specified object model is unavailable.
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* @throws NullPointerException If <code>uri</code> is <code>null</code>.
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* @throws IllegalArgumentException If <code>uri.length() == 0</code>.
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*/
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public static final XPathFactory newInstance(final String uri)
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throws XPathFactoryConfigurationException {
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if (uri == null) {
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throw new NullPointerException("uri == null");
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}
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if (uri.length() == 0) {
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throw new IllegalArgumentException(
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"XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
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);
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}
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ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
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if (classLoader == null) {
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//use the current class loader
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classLoader = XPathFactory.class.getClassLoader();
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}
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XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).newFactory(uri);
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if (xpathFactory == null) {
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throw new XPathFactoryConfigurationException(
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"No XPathFactory implementation found for the object model: "
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+ uri
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);
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}
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return xpathFactory;
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}
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/**
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* @return Instance of an <code>XPathFactory</code>.
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*
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* @throws XPathFactoryConfigurationException If the specified object model is unavailable.
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* @throws NullPointerException If <code>uri</code> is <code>null</code>.
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* @throws IllegalArgumentException If <code>uri.length() == 0</code>.
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*/
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public static XPathFactory newInstance(String uri, String factoryClassName,
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ClassLoader classLoader) throws XPathFactoryConfigurationException {
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if (uri == null) {
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throw new NullPointerException("uri == null");
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}
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if (uri.length() == 0) {
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throw new IllegalArgumentException(
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"XPathFactory#newInstance(String uri) cannot be called with uri == \"\""
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);
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}
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if (factoryClassName == null) {
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throw new XPathFactoryConfigurationException("factoryClassName cannot be null.");
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}
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if (classLoader == null) {
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classLoader = Thread.currentThread().getContextClassLoader();
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}
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XPathFactory xpathFactory = new XPathFactoryFinder(classLoader).createInstance(factoryClassName);
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if (xpathFactory == null || !xpathFactory.isObjectModelSupported(uri)) {
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throw new XPathFactoryConfigurationException(
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"No XPathFactory implementation found for the object model: "
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+ uri
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);
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}
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return xpathFactory;
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}
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/**
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* <p>Is specified object model supported by this <code>XPathFactory</code>?</p>
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*
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* @param objectModel Specifies the object model which the returned <code>XPathFactory</code> will understand.
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*
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* @return <code>true</code> if <code>XPathFactory</code> supports <code>objectModel</code>, else <code>false</code>.
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*
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* @throws NullPointerException If <code>objectModel</code> is <code>null</code>.
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* @throws IllegalArgumentException If <code>objectModel.length() == 0</code>.
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*/
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public abstract boolean isObjectModelSupported(String objectModel);
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/**
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* <p>Set a feature for this <code>XPathFactory</code> and <code>XPath</code>s created by this factory.</p>
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*
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* <p>
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* Feature names are fully qualified {@link java.net.URI}s.
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* Implementations may define their own features.
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* An {@link XPathFactoryConfigurationException} is thrown if this <code>XPathFactory</code> or the <code>XPath</code>s
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* it creates cannot support the feature.
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* It is possible for an <code>XPathFactory</code> to expose a feature value but be unable to change its state.
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* </p>
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*
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* <p>
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* All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING} feature.
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* When the feature is <code>true</code>, any reference to an external function is an error.
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* Under these conditions, the implementation must not call the {@link XPathFunctionResolver}
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* and must throw an {@link XPathFunctionException}.
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* </p>
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*
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* @param name Feature name.
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* @param value Is feature state <code>true</code> or <code>false</code>.
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*
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* @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s
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* it creates cannot support this feature.
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* @throws NullPointerException if <code>name</code> is <code>null</code>.
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*/
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public abstract void setFeature(String name, boolean value)
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throws XPathFactoryConfigurationException;
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/**
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* <p>Get the state of the named feature.</p>
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*
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* <p>
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* Feature names are fully qualified {@link java.net.URI}s.
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* Implementations may define their own features.
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* An {@link XPathFactoryConfigurationException} is thrown if this <code>XPathFactory</code> or the <code>XPath</code>s
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* it creates cannot support the feature.
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* It is possible for an <code>XPathFactory</code> to expose a feature value but be unable to change its state.
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* </p>
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*
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* @param name Feature name.
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*
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* @return State of the named feature.
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*
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* @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s
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* it creates cannot support this feature.
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* @throws NullPointerException if <code>name</code> is <code>null</code>.
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*/
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public abstract boolean getFeature(String name)
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throws XPathFactoryConfigurationException;
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/**
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* <p>Establish a default variable resolver.</p>
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*
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* <p>Any <code>XPath</code> objects constructed from this factory will use
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* the specified resolver by default.</p>
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*
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* <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
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*
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* @param resolver Variable resolver.
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*
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* @throws NullPointerException If <code>resolver</code> is <code>null</code>.
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*/
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public abstract void setXPathVariableResolver(XPathVariableResolver resolver);
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/**
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* <p>Establish a default function resolver.</p>
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*
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* <p>Any <code>XPath</code> objects constructed from this factory will use
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* the specified resolver by default.</p>
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*
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* <p>A <code>NullPointerException</code> is thrown if <code>resolver</code> is <code>null</code>.</p>
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*
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* @param resolver XPath function resolver.
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*
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* @throws NullPointerException If <code>resolver</code> is <code>null</code>.
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*/
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public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver);
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/**
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* <p>Return a new <code>XPath</code> using the underlying object
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* model determined when the <code>XPathFactory</code> was instantiated.</p>
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*
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* @return New instance of an <code>XPath</code>.
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*/
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public abstract XPath newXPath();
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}
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