/*
 * The contents of this file are subject to the terms
 * of the Common Development and Distribution License
 * (the "License").  You may not use this file except
 * in compliance with the License.
 *
 * You can obtain a copy of the license at
 * https://jaxp.dev.java.net/CDDLv1.0.html.
 * See the License for the specific language governing
 * permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL
 * HEADER in each file and include the License file at
 * https://jaxp.dev.java.net/CDDLv1.0.html
 * If applicable add the following below this CDDL HEADER
 * with the fields enclosed by brackets "[]" replaced with
 * your own identifying information: Portions Copyright
 * [year] [name of copyright owner]
 */

/*
 * $Id: XMLEntityReader.java,v 1.3 2005/11/03 17:02:21 jeffsuttor Exp $
 * @(#)XPath.java	1.19 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
 */

package javax.xml.xpath;

import org.xml.sax.InputSource;
import javax.xml.namespace.QName;
import javax.xml.namespace.NamespaceContext;

/**
 * <p><code>XPath</code> provides access to the XPath evaluation environment and expressions.</p>
 *
 * <a name="XPath-evaluation"/>
 * <table border="1" cellpadding="2">
 *   <thead>
 *     <tr>
 *       <th colspan="2">Evaluation of XPath Expressions.</th>
 *     </tr>
 *   </thead>
 *   <tbody>
 *     <tr>
 *       <td>context</td>
 *       <td>
 *         If a request is made to evaluate the expression in the absence
 * of a context item, an empty document node will be used for the context.
 * For the purposes of evaluating XPath expressions, a DocumentFragment
 * is treated like a Document node.
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>variables</td>
 *      <td>
 *        If the expression contains a variable reference, its value will be found through the {@link XPathVariableResolver}

 *        set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}.
 *        An {@link XPathExpressionException} is raised if the variable resolver is undefined or
 *        the resolver returns <code>null</code> for the variable.
 *        The value of a variable must be immutable through the course of any single evaluation.</p>
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>functions</td>
 *      <td>
 *        If the expression contains a function reference, the function will be found through the {@link 
XPathFunctionResolver}
 *        set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}.
 *        An {@link XPathExpressionException} is raised if the function resolver is undefined or
 *        the function resolver returns <code>null</code> for the function.</p>
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>QNames</td>
 *      <td>
 *        QNames in the expression are resolved against the XPath namespace context
 *        set with {@link #setNamespaceContext(NamespaceContext nsContext)}.
 *      </td>
 *    </tr>
 *    <tr>
 *      <td>result</td>
 *      <td>
 *        This result of evaluating an expression is converted to an instance of the desired return type.
 *        Valid return types are defined in {@link XPathConstants}.
 *        Conversion to the return type follows XPath conversion rules.</p>
 *      </td>
 *    </tr>
 * </table>
 *
 * <p>An XPath object is not thread-safe and not reentrant.
 * In other words, it is the application's responsibility to make
 * sure that one {@link XPath} object is not used from
 * more than one thread at any given time, and while the <code>evaluate</code>
 * method is invoked, applications may not recursively call
 * the <code>evaluate</code> method.
 * <p>
 * 
 * @author  <a href="Norman.Walsh@Sun.com">Norman Walsh</a>
 * @author  <a href="Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @version $Revision: 1.5 $, $Date: 2005/10/13 17:00:49 $