/*

 * Copyright 2003-2005 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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 */

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>

 * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0</a>

 * @since 1.5

 */

public interface XPath {

        /**

         * <p>Reset this <code>XPath</code> to its original configuration.</p>

         *

         * <p><code>XPath</code> is reset to the same state as when it was created with

         * {@link XPathFactory#newXPath()}.

         * <code>reset()</code> is designed to allow the reuse of existing <code>XPath</code>s

         * thus saving resources associated with the creation of new <code>XPath</code>s.</p>

         *

         * <p>The reset <code>XPath</code> is not guaranteed to have the same {@link XPathFunctionResolver}, {@link XPathVariableResolver}

         * or {@link NamespaceContext} <code>Object</code>s, e.g. {@link Object#equals(Object obj)}.

         * It is guaranteed to have a functionally equal <code>XPathFunctionResolver</code>, <code>XPathVariableResolver</code>

         * and <code>NamespaceContext</code>.</p>

         */

        public void reset();

    /**

     * <p>Establish a variable resolver.</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 void setXPathVariableResolver(XPathVariableResolver resolver);

    /**

       * <p>Return the current variable resolver.</p>

       *

       * <p><code>null</code> is returned in no variable resolver is in effect.</p>

       *

       * @return Current variable resolver.

       */

    public XPathVariableResolver getXPathVariableResolver();

    /**

       * <p>Establish a function resolver.</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 void setXPathFunctionResolver(XPathFunctionResolver resolver);

    /**

       * <p>Return the current function resolver.</p>

       *

       * <p><code>null</code> is returned in no function resolver is in effect.</p>

       *

       * @return Current function resolver.

       */

    public XPathFunctionResolver getXPathFunctionResolver();

    /**

       * <p>Establish a namespace context.</p>

       *

       * <p>A <code>NullPointerException</code> is thrown if <code>nsContext</code> is <code>null</code>.</p>

       *

       * @param nsContext Namespace context to use.

       *

       * @throws NullPointerException If <code>nsContext</code> is <code>null</code>.

       */

    public void setNamespaceContext(NamespaceContext nsContext);

    /**

       * <p>Return the current namespace context.</p>

       *

       * <p><code>null</code> is returned in no namespace context is in effect.</p>

       *

       * @return Current Namespace context.

       */

    public NamespaceContext getNamespaceContext();

    /**

       * <p>Compile an XPath expression for later evaluation.</p>

       *

       * <p>If <code>expression</code> contains any {@link XPathFunction}s,

       * they must be available via the {@link XPathFunctionResolver}.

       * An {@link XPathExpressionException} will be thrown if the

       * <code>XPathFunction</code>

       * cannot be resovled with the <code>XPathFunctionResolver</code>.</p>

       *

       * <p>If <code>expression</code> contains any variables, the

       * {@link XPathVariableResolver} in effect

       * <strong>at compile time</strong> will be used to resolve them.</p>

       *

       * <p>If <code>expression</code> is <code>null</code>, a <code>NullPointerException</code> is thrown.</p>

       *

       * @param expression The XPath expression.

       *

       * @return Compiled XPath expression.

       * @throws XPathExpressionException If <code>expression</code> cannot be compiled.

       * @throws NullPointerException If <code>expression</code> is <code>null</code>.

       */

    public XPathExpression compile(String expression)

        throws XPathExpressionException;

    /**

     * <p>Evaluate an <code>XPath</code> expression in the specified context and return the result as the specified type.</p>

     *

     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and <code>QName</code> resolution and return type conversion.</p>

     *

     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants} (

     * {@link XPathConstants#NUMBER NUMBER},

     * {@link XPathConstants#STRING STRING},

     * {@link XPathConstants#BOOLEAN BOOLEAN},

     * {@link XPathConstants#NODE NODE} or

     * {@link XPathConstants#NODESET NODESET})

     * then an <code>IllegalArgumentException</code> is thrown.</p>

     *

     * <p>If a <code>null</code> value is provided for

     * <code>item</code>, an empty document will be used for the

     * context.

     * If <code>expression</code> or <code>returnType</code> is <code>null</code>, then a

     * <code>NullPointerException</code> is thrown.</p>

     *

     * @param expression The XPath expression.

     * @param item The starting context (a node, for example).

     * @param returnType The desired return type.

     *

     * @return Result of evaluating an XPath expression as an <code>Object</code> of <code>returnType</code>.

     *

     * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.

     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.

     * @throws NullPointerException If <code>expression</code> or <code>returnType</code> is <code>null</code>.

     */

    public Object evaluate(String expression, Object item, QName returnType)

        throws XPathExpressionException;

    /**

     * <p>Evaluate an XPath expression in the specified context and return the result as a <code>String</code>.</p>

     *

     * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a <code>returnType</code> of

     * {@link XPathConstants#STRING}.</p>

     *

     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.</p>

     *

     * <p>If a <code>null</code> value is provided for

     * <code>item</code>, an empty document will be used for the

     * context.

     * If <code>expression</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>

     *

     * @param expression The XPath expression.

     * @param item The starting context (a node, for example).

     *

     * @return The <code>String</code> that is the result of evaluating the expression and

     *   converting the result to a <code>String</code>.

     *

     * @throws XPathExpressionException If <code>expression</code> cannot be evaluated.

     * @throws NullPointerException If <code>expression</code> is <code>null</code>.

     */

    public String evaluate(String expression, Object item)

        throws XPathExpressionException;

    /**

     * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>

     * and return the result as the specified type.</p>

     *

     * <p>This method builds a data model for the {@link InputSource} and calls

     * {@link #evaluate(String expression, Object item, QName returnType)} on the resulting document object.</p>

     *

     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.</p>

     *

     * <p>If <code>returnType</code> is not one of the types defined in {@link XPathConstants},

     * then an <code>IllegalArgumentException</code> is thrown.</p>

     *

     * <p>If <code>expression</code>, <code>source</code> or <code>returnType</code> is <code>null</code>,

     * then a <code>NullPointerException</code> is thrown.</p>

     *

     * @param expression The XPath expression.

     * @param source The input source of the document to evaluate over.

     * @param returnType The desired return type.

     *

     * @return The <code>Object</code> that encapsulates the result of evaluating the expression.

     *

     * @throws XPathExpressionException If expression cannot be evaluated.

     * @throws IllegalArgumentException If <code>returnType</code> is not one of the types defined in {@link XPathConstants}.

     * @throws NullPointerException If <code>expression</code>, <code>source</code> or <code>returnType</code>

     *   is <code>null</code>.

     */

    public Object evaluate(

        String expression,

        InputSource source,

        QName returnType)

        throws XPathExpressionException;

    /**

     * <p>Evaluate an XPath expression in the context of the specified <code>InputSource</code>

     * and return the result as a <code>String</code>.</p>

     *

     * <p>This method calls {@link #evaluate(String expression, InputSource source, QName returnType)} with a

     * <code>returnType</code> of {@link XPathConstants#STRING}.</p>

     *

     * <p>See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a> for context item evaluation,

     * variable, function and QName resolution and return type conversion.</p>

     *

     * <p>If <code>expression</code> or <code>source</code> is <code>null</code>,

     * then a <code>NullPointerException</code> is thrown.</p>

     *

     * @param expression The XPath expression.

     * @param source The <code>InputSource</code> of the document to evaluate over.

     *

     * @return The <code>String</code> that is the result of evaluating the expression and

     *   converting the result to a <code>String</code>.

     *

     * @throws XPathExpressionException If expression cannot be evaluated.

     * @throws NullPointerException If <code>expression</code> or <code>source</code> is <code>null</code>.

     */

    public String evaluate(String expression, InputSource source)

        throws XPathExpressionException;

}