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   *  GNU General Public License for more details.
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   *  You should have received a copy of the GNU General Public License
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  /*
   * 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 jaxp.xml.xpath;
  
  import jaxp.xml.XMLConstants;
  
  /**
   * <p>An <code>XPathFactory</code> instance can be used to create
   * {@link XPath} objects.</p>
   *
   *<p>See {@link #newInstance(String uri)} for lookup mechanism.</p>
   *
   * <p>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 <code>synchronized</code> to protect themselves from broken clients.
   *
   * <p>{@link XPathFactory} is not re-entrant. While one of the
   * <code>newInstance</code> methods is being invoked, applications
   * may not attempt to recursively invoke a <code>newInstance</code> method,
   * even from the same thread.
   *
   * @author  <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
   * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
   *
   * @since 1.5
   */
  public abstract class XPathFactory {
  
  
      /**
       * <p>The default property name according to the JAXP spec.</p>
       */
      public static final String DEFAULT_PROPERTY_NAME = "javax.xml.xpath.XPathFactory";
  
      /**
       * <p>Default Object Model URI.</p>
       */
      public static final String DEFAULT_OBJECT_MODEL_URI = "http://java.sun.com/jaxp/xpath/dom";
  
      /**
       *<p> Take care of restrictions imposed by java security model </p>
       */
      private static SecuritySupport ss = new SecuritySupport() ;
  
      /**
       * <p>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 <code>XPathFactory</code>.</p>
       */
      protected XPathFactory() {
      }
  
      /**
       * <p>Get a new <code>XPathFactory</code> instance using the default object model,
       * {@link #DEFAULT_OBJECT_MODEL_URI},
       * the W3C DOM.</p>
       *
       * <p>This method is functionally equivalent to:</p>
       * <pre>
       *   newInstance(DEFAULT_OBJECT_MODEL_URI)
       * </pre>
       *
       * <p>Since the implementation for the W3C DOM is always available, this method will never fail.</p>
       *
       * @return Instance of an <code>XPathFactory</code>.
       *
       * @throws RuntimeException When there is a failure in creating an
       *   <code>XPathFactory</code> 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()
                  );
          }
      }
  
      /**
      * <p>Get a new <code>XPathFactory</code> instance using the specified object model.</p>
      *
      * <p>To find a <code>XPathFactory</code> object,
      * this method looks the following places in the following order where "the class loader" refers to the context class loader:</p>
      * <ol>
      *   <li>
      *     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.
      *   </li>
      *   <li>
      *     ${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.
      *   </li>
      *   <li>
      *     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.
      *     <br>
      *     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.
      *     <br>
      *     In case of {@link java.util.ServiceConfigurationError} an
      *     {@link XPathFactoryConfigurationException} will be thrown.
      *   </li>
      *   <li>
      *     Platform default <code>XPathFactory</code> 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}.
      *   </li>
      * </ol>
      * <p>If everything fails, an <code>XPathFactoryConfigurationException</code> will be thrown.</p>
      *
      * <p>Tip for Trouble-shooting:</p>
      * <p>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:</p>
      * <pre>
      *   http\://java.sun.com/jaxp/xpath/dom=org.acme.DomXPathFactory
      * </pre>
      *
      * @param uri Identifies the underlying object model.
      *   The specification only defines the URI {@link #DEFAULT_OBJECT_MODEL_URI},
      *   <code>http://java.sun.com/jaxp/xpath/dom</code> 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 <code>XPathFactory</code>.
      *
      * @throws XPathFactoryConfigurationException If the specified object model
      *      is unavailable, or if there is a configuration error.
      * @throws NullPointerException If <code>uri</code> is <code>null</code>.
      * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
      *   or <code>uri.length() == 0</code>.
      */
      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;
      }
  
      /**
       * <p>Obtain a new instance of a <code>XPathFactory</code> from a factory class name. <code>XPathFactory</code>
       * 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.</p>
       *
       *
       * <h2>Tip for Trouble-shooting</h2>
       * <p>Setting the <code>jaxp.debug</code> system property will cause
       * this method to print a lot of debug messages
       * to <code>System.err</code> about what it is doing and where it is looking at.</p>
       *
       * <p> If you have problems try:</p>
       * <pre>
       * java -Djaxp.debug=1 YourProgram ....
       * </pre>
       *
       * @param uri         Identifies the underlying object model. The specification only defines the URI
       *                    {@link #DEFAULT_OBJECT_MODEL_URI},<code>http://java.sun.com/jaxp/xpath/dom</code>
       *                    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 <code>javax.xml.xpath.XPathFactory</code>.
       *
       * @param classLoader <code>ClassLoader</code> used to load the factory class. If <code>null</code>
       *                     current <code>Thread</code>'s context classLoader is used to load the factory class.
       *
       *
       * @return New instance of a <code>XPathFactory</code>
       *
       * @throws XPathFactoryConfigurationException
       *                   if <code>factoryClassName</code> is <code>null</code>, or
       *                   the factory class cannot be loaded, instantiated
       *                   or the factory class does not support the object model specified
       *                   in the <code>uri</code> parameter.
       *
       * @throws NullPointerException If <code>uri</code> is <code>null</code>.
       * @throws IllegalArgumentException If <code>uri</code> is <code>null</code>
       *          or <code>uri.length() == 0</code>.
       *
       * @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");
          }
  
      }
  
      /**
       * <p>Is specified object model supported by this <code>XPathFactory</code>?</p>
       *
       * @param objectModel Specifies the object model which the returned <code>XPathFactory</code> will understand.
       *
       * @return <code>true</code> if <code>XPathFactory</code> supports <code>objectModel</code>, else <code>false</code>.
       *
       * @throws NullPointerException If <code>objectModel</code> is <code>null</code>.
       * @throws IllegalArgumentException If <code>objectModel.length() == 0</code>.
       */
      public abstract boolean isObjectModelSupported(String objectModel);
  
      /**
       * <p>Set a feature for this <code>XPathFactory</code> and
       * <code>XPath</code>s created by this factory.</p>
       *
       * <p>
       * Feature names are fully qualified {@link java.net.URI}s.
       * Implementations may define their own features.
       * An {@link XPathFactoryConfigurationException} is thrown if this
       * <code>XPathFactory</code> or the <code>XPath</code>s
       * it creates cannot support the feature.
       * It is possible for an <code>XPathFactory</code> to expose a feature value
       * but be unable to change its state.
       * </p>
       *
       * <p>
       * All implementations are required to support the {@link XMLConstants#FEATURE_SECURE_PROCESSING} feature.
       * When the feature is <code>true</code>, 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}.
       * </p>
       *
       * @param name Feature name.
       * @param value Is feature state <code>true</code> or <code>false</code>.
       *
       * @throws XPathFactoryConfigurationException if this <code>XPathFactory</code> or the <code>XPath</code>s
       *   it creates cannot support this feature.
       * @throws NullPointerException if <code>name</code> is <code>null</code>.
       */
      public abstract void setFeature(String name, boolean value)
              throws XPathFactoryConfigurationException;
  
      /**
       * <p>Get the state of the named feature.</p>
       *
       * <p>
       * Feature names are fully qualified {@link java.net.URI}s.
       * Implementations may define their own features.
       * An {@link XPathFactoryConfigurationException} is thrown if this
       * <code>XPathFactory</code> or the <code>XPath</code>s
       * it creates cannot support the feature.
       * It is possible for an <code>XPathFactory</code> to expose a feature value
       * but be unable to change its state.
       * </p>
       *
       * @param name Feature name.
       *
       * @return State of the named feature.
       *
       * @throws XPathFactoryConfigurationException if this
       *   <code>XPathFactory</code> or the <code>XPath</code>s
       *   it creates cannot support this feature.
       * @throws NullPointerException if <code>name</code> is <code>null</code>.
       */
      public abstract boolean getFeature(String name)
              throws XPathFactoryConfigurationException;
  
      /**
       * <p>Establish a default variable resolver.</p>
       *
       * <p>Any <code>XPath</code> objects constructed from this factory will use
       * the specified resolver by default.</p>
       *
       * <p>A <code>NullPointerException</code> is thrown if <code>resolver</code>
       * is <code>null</code>.</p>
       *
       * @param resolver Variable resolver.
       *
       * @throws NullPointerException If <code>resolver</code> is
       *   <code>null</code>.
       */
      public abstract void setXPathVariableResolver(XPathVariableResolver resolver);
  
      /**
       * <p>Establish a default function resolver.</p>
       *
       * <p>Any <code>XPath</code> objects constructed from this factory will
       * use the specified resolver by default.</p>
       *
       * <p>A <code>NullPointerException</code> is thrown if
       * <code>resolver</code> is <code>null</code>.</p>
       *
       * @param resolver XPath function resolver.
       *
       * @throws NullPointerException If <code>resolver</code> is
       *   <code>null</code>.
       */
      public abstract void setXPathFunctionResolver(XPathFunctionResolver resolver);
  
      /**
      * <p>Return a new <code>XPath</code> using the underlying object
      * model determined when the <code>XPathFactory</code> was instantiated.</p>
      *
      * @return New instance of an <code>XPath</code>.
      */
      public abstract XPath newXPath();
  }
  