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

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package javax.xml.xpath;

import javax.xml.namespace.NamespaceContext;

import javax.xml.namespace.QName;

import org.xml.sax.InputSource;

/**

 * {@code XPath} provides access to the XPath evaluation environment and expressions.

 * The XPath evaluation is affected by the factors described in the following table.

 *

 * <a id="XPath-evaluation"></a>

 * <table class="striped">

 *    <caption>Evaluation of XPath Expressions</caption>

 *    <thead>

 *      <tr>

 *        <th scope="col">Factor</th>

 *        <th scope="col">Behavior</th>

 *      </tr>

 *    </thead>

 *    <tbody>

 *    <tr>

 *      <th scope="row">context</th>

 *      <td>

 *        The type of the context is implementation-dependent. If the value is

 *        null, the operation must have no dependency on the context, otherwise

 *        an XPathExpressionException will be thrown.

 *

 *        For the purposes of evaluating XPath expressions, a DocumentFragment

 *        is treated like a Document node.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">variables</th>

 *      <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} for the variable.

 *        The value of a variable must be immutable through the course of any single evaluation.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">functions</th>

 *      <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} for the function.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">QNames</th>

 *      <td>

 *        QNames in the expression are resolved against the XPath namespace context

 *        set with {@link #setNamespaceContext(NamespaceContext nsContext)}.

 *      </td>

 *    </tr>

 *    <tr>

 *      <th scope="row">result</th>

 *      <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.

 *      </td>

 *    </tr>

 *    </tbody>

 * </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}

 * method is invoked, applications may not recursively call

 * the {@code evaluate} method.

 *

 * @author  Norman Walsh

 * @author  Jeff Suttor

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

 * @since 1.5

 */

public interface XPath {

    /**

     * Reset this {@code XPath} to its original configuration.

     *

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

     * {@link XPathFactory#newXPath()}.

     * {@code reset()} is designed to allow the reuse of existing {@code XPath}s

     * thus saving resources associated with the creation of new {@code XPath}s.

     *

     * <p>The reset {@code XPath} is not guaranteed to have the same

     * {@link XPathFunctionResolver}, {@link XPathVariableResolver}

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

     * It is guaranteed to have a functionally equal {@code XPathFunctionResolver},

     * {@code XPathVariableResolver} and {@code NamespaceContext}.

     */

    public void reset();

    /**

     * Establish a variable resolver.

     *

     * <p>A {@code NullPointerException} is thrown if {@code resolver} is {@code null}.

     *

     * @param resolver Variable resolver.

     *

     * @throws NullPointerException If {@code resolver} is {@code null}.

     */

    public void setXPathVariableResolver(XPathVariableResolver resolver);

    /**

       * Return the current variable resolver.

       *

       * <p>{@code null} is returned in no variable resolver is in effect.

       *

       * @return Current variable resolver.

       */

    public XPathVariableResolver getXPathVariableResolver();

    /**

       * Establish a function resolver.

       *

       * <p>A {@code NullPointerException} is thrown if {@code resolver} is {@code null}.

       *

       * @param resolver XPath function resolver.

       *

       * @throws NullPointerException If {@code resolver} is {@code null}.

       */

    public void setXPathFunctionResolver(XPathFunctionResolver resolver);

    /**

       * Return the current function resolver.

       * <p>

       * {@code null} is returned in no function resolver is in effect.

       *

       * @return Current function resolver.

       */

    public XPathFunctionResolver getXPathFunctionResolver();

    /**

       * Establish a namespace context.

       *

       * <p>A {@code NullPointerException} is thrown if {@code nsContext} is {@code null}.

       *

       * @param nsContext Namespace context to use.

       *

       * @throws NullPointerException If {@code nsContext} is {@code null}.

       */

    public void setNamespaceContext(NamespaceContext nsContext);

    /**

       * Return the current namespace context.

       *

       * <p>{@code null} is returned in no namespace context is in effect.

       *

       * @return Current Namespace context.

       */

    public NamespaceContext getNamespaceContext();

    /**

       * Compile an XPath expression for later evaluation.

       *

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

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

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

       * {@code XPathFunction}

       * cannot be resovled with the {@code XPathFunctionResolver}.

       *

       * <p>If {@code expression} contains any variables, the

       * {@link XPathVariableResolver} in effect

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

       *

       * @param expression The XPath expression.

       *

       * @return Compiled XPath expression.

       * @throws XPathExpressionException If {@code expression} cannot be compiled.

       * @throws NullPointerException If {@code expression} is {@code null}.

       */

    public XPathExpression compile(String expression)

        throws XPathExpressionException;

    /**

     * Evaluate an {@code XPath} expression in the specified context and

     * return the result as the specified type.

     *

     * <p>

     * See <a href="#XPath-evaluation">Evaluation of XPath Expressions</a>

     * for context item evaluation, variable, function and {@code QName} resolution

     * and return type conversion.

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @param expression The XPath expression.

     * @param item The context the XPath expression will be evaluated in.

     * @param returnType The result type expected to be returned by the XPath expression.

     *

     * @return The result of evaluating an XPath expression as an {@code Object} of {@code returnType}.

     *

     * @throws XPathExpressionException If {@code expression} cannot be evaluated.

     * @throws IllegalArgumentException If {@code returnType} 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}).

     * @throws NullPointerException If {@code expression or returnType} is {@code null}.

     */

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

        throws XPathExpressionException;

    /**

     * Evaluate an XPath expression in the specified context and return the result as a {@code String}.

     *

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

     * {@link XPathConstants#STRING}.

     *

     * <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>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @param expression The XPath expression.

     * @param item The context the XPath expression will be evaluated in.

     *

     * @return The result of evaluating an XPath expression as a {@code String}.

     *

     * @throws XPathExpressionException If {@code expression} cannot be evaluated.

     * @throws NullPointerException If {@code expression} is {@code null}.

     */

    public String evaluate(String expression, Object item)

        throws XPathExpressionException;

    /**

     * Evaluate an XPath expression in the context of the specified {@code InputSource}

     * and return the result as the specified type.

     *

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

     * variable, function and QName resolution and return type conversion.

     *

     * @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} that encapsulates the result of evaluating the expression.

     *

     * @throws XPathExpressionException If expression cannot be evaluated.

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

     * @throws NullPointerException If {@code expression, source or returnType} is {@code null}.

     */

    public Object evaluate(

        String expression,

        InputSource source,

        QName returnType)

        throws XPathExpressionException;

    /**

     * Evaluate an XPath expression in the context of the specified {@code InputSource}

     * and return the result as a {@code String}.

     *

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

     * {@code returnType} of {@link XPathConstants#STRING}.

     *

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

     * variable, function and QName resolution and return type conversion.

     *

     * @param expression The XPath expression.

     * @param source The {@code InputSource} of the document to evaluate over.

     *

     * @return The {@code String} that is the result of evaluating the expression and

     *   converting the result to a {@code String}.

     *

     * @throws XPathExpressionException If expression cannot be evaluated.

     * @throws NullPointerException If {@code expression or source} is {@code null}.

     */

    public String evaluate(String expression, InputSource source)

        throws XPathExpressionException;

    /**

     * Evaluate an XPath expression in the specified context and return

     * the result with the type specified through the {@code class type}

     *

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

     *     (T)evaluate(expression, item,

     *           XPathEvaluationResult.XPathResultType.getQNameType(type));

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying

     * XPathEvaluationResult as the type will result in IllegalArgumentException.

     * Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override

     * this method.

     *

     * @param <T> The class type that will be returned by the XPath expression.

     * @param expression The XPath expression.

     * @param item The context the XPath expression will be evaluated in.

     * @param type The class type expected to be returned by the XPath expression.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If {@code type} is not of the types

     * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType},

     * or XPathEvaluationResult is specified as the type but an implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type is not available.

     * @throws NullPointerException If {@code expression or type} is {@code null}.

     *

     * @since 9

     */

    default <T>T evaluateExpression(String expression, Object item, Class<T> type)

        throws XPathExpressionException {

        return type.cast(evaluate(expression, item,

                XPathEvaluationResult.XPathResultType.getQNameType(type)));

    }

    /**

     * Evaluate an XPath expression in the specified context. This is equivalent to

     * calling {@link #evaluateExpression(String expression, Object item, Class type)}

     * with type {@link XPathEvaluationResult}:

     * <pre> {@code

     *     evaluateExpression(expression, item, XPathEvaluationResult.class);

     * }</pre>

     * <p>

     * The parameter {@code item} represents the context the XPath expression

     * will be operated on. The type of the context is implementation-dependent.

     * If the value is {@code null}, the operation must have no dependency on

     * the context, otherwise an XPathExpressionException will be thrown.

     *

     * @implNote

     * The type of the context is usually {@link org.w3c.dom.Node}.

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

     *     evaluateExpression(expression, item, XPathEvaluationResult.class);

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY}

     * type, the default implementation of this method will always throw an

     * IllegalArgumentException. Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore

     * override this method.

     *

     * @param expression The XPath expression.

     * @param item The context the XPath expression will be evaluated in.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If the implementation of this method

     * does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.

     * @throws NullPointerException If {@code expression} is {@code null}.

     *

     * @since 9

     */

    default XPathEvaluationResult<?> evaluateExpression(String expression, Object item)

        throws XPathExpressionException

    {

        return evaluateExpression(expression, item, XPathEvaluationResult.class);

    }

    /**

     * Evaluate an XPath expression in the context of the specified {@code source}

     * and return the result as specified.

     * <p>

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

     * {@link #evaluateExpression(String expression, Object item, Class type)}

     * on the resulting document object. The data model is usually

     * {@link org.w3c.dom.Document}

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

           (T)evaluate(expression, source,

                XPathEvaluationResult.XPathResultType.getQNameType(type));

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type, specifying

     * XPathEvaluationResult as the type will result in IllegalArgumentException.

     * Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must override

     * this method.

     *

     * @param <T> The class type that will be returned by the XPath expression.

     * @param expression The XPath expression.

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

     * @param type The class type expected to be returned by the XPath expression.

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If {@code type} is not of the types

     * corresponding to the types defined in the {@link XPathEvaluationResult.XPathResultType

     * XPathResultType}, or XPathEvaluationResult is specified as the type but an

     * implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type is not available.

     * @throws NullPointerException If {@code expression, source or type}is {@code null}.

     *

     * @since 9

     */

    default <T>T evaluateExpression(String expression, InputSource source, Class<T> type)

        throws XPathExpressionException

    {

        return type.cast(evaluate(expression, source,

                XPathEvaluationResult.XPathResultType.getQNameType(type)));

    }

    /**

     * Evaluate an XPath expression in the specified context. This is equivalent to

     * calling {@link #evaluateExpression(String expression, Object item, Class type)}

     * with type {@link XPathEvaluationResult}:

     * <pre> {@code

     *     evaluateExpression(expression, item, XPathEvaluationResult.class);

     * }</pre>

     *

     * @implSpec

     * The default implementation in the XPath API is equivalent to:

     * <pre> {@code

     *     evaluateExpression(expression, source, XPathEvaluationResult.class);

     * }</pre>

     *

     * Since the {@code evaluate} method does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY}

     * type, the default implementation of this method will always throw an

     * IllegalArgumentException. Any implementation supporting the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type must therefore

     * override this method.

     *

     * @param expression The XPath expression.

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

     *

     * @return The result of evaluating the expression.

     *

     * @throws XPathExpressionException If the expression cannot be evaluated.

     * @throws IllegalArgumentException If the implementation of this method

     * does not support the

     * {@link XPathEvaluationResult.XPathResultType#ANY ANY} type.

     * @throws NullPointerException If {@code expression or source} is {@code null}.

     *

     * @since 9

     */

    default XPathEvaluationResult<?> evaluateExpression(String expression, InputSource source)

        throws XPathExpressionException