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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * published by the Free Software Foundation.  Oracle designates this

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

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 * 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

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 * accompanied this code).

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package javax.xml.xpath;

import org.xml.sax.InputSource;

import javax.xml.namespace.QName;

/**

 * <p><code>XPathExpression</code> provides access to compiled XPath expressions.</p>

 *

 * <a name="XPathExpression-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}.

 *        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}.

 *        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.

 *      </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 expression is not thread-safe and not reentrant.

 * In other words, it is the application's responsibility to make

 * sure that one {@link XPathExpression} 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="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>

 * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>

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

 * @since 1.5

 */

public interface XPathExpression {

    /**

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

     *

     * <p>See <a href="#XPathExpression-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 a <code>null</code> value is provided for

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

     * context.

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

     *

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

     * @param returnType The desired return type.

     *

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

     *   <code>returnType</code>.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

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

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

     */

    public Object evaluate(Object item, QName returnType)

        throws XPathExpressionException;

    /**

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

     *

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

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

     *

     * <p>See <a href="#XPathExpression-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.

     *

     * @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 the expression cannot be evaluated.

     */

    public String evaluate(Object item)

        throws XPathExpressionException;

    /**

     * <p>Evaluate the compiled 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(Object item, QName returnType)} on the resulting document object.</p>

     *

     * <p>See <a href="#XPathExpression-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>source</code> or <code>returnType</code> is <code>null</code>,

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

     *

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

     * @param returnType The desired return type.

     *

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

     *   <code>returnType</code>.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

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

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

     */

    public Object evaluate(InputSource source, QName returnType)

        throws XPathExpressionException;

    /**

     * <p>Evaluate the compiled 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(InputSource source, QName returnType)} with a <code>returnType</code> of

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

     *

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

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

     *

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

     *

     * @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 the expression cannot be evaluated.

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

     */

    public String evaluate(InputSource source)

        throws XPathExpressionException;

}