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* <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> * 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.</p> * </td> * </tr> * <tr> * <td>functions * <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> * <td>QNames * <td> * QNames in the expression are resolved against the XPath namespace context * set with {@link #setNamespaceContext(NamespaceContext nsContext)}. * </td> * </tr> * <tr> * <td>result * <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 * method is invoked, applications may not recursively call * the <code>evaluate method. * <p> * * @author <a href="Norman.Walsh@Sun.com">Norman Walsh * @author <a href="Jeff.Suttor@Sun.com">Jeff Suttor * @see <a href="http://www.w3.org/TR/xpath">XML Path Language (XPath) Version 1.0 * @since 1.5 */ public interface XPath { /** * <p>Reset this XPath to its original configuration.

* * <p>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 XPaths * thus saving resources associated with the creation of new <code>XPaths.

* * <p>The reset XPath is not guaranteed to have the same {@link XPathFunctionResolver}, {@link XPathVariableResolver} * or {@link NamespaceContext} <code>Objects, e.g. {@link Object#equals(Object obj)}. * It is guaranteed to have a functionally equal <code>XPathFunctionResolver, XPathVariableResolver * and <code>NamespaceContext.

*/ public void reset(); /** * <p>Establish a variable resolver.

* * <p>A NullPointerException is thrown if resolver is null.

* * @param resolver Variable resolver. * * @throws NullPointerException If <code>resolver is null. */ public void setXPathVariableResolver(XPathVariableResolver resolver); /** * <p>Return the current variable resolver.

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

* * @return Current variable resolver. */ public XPathVariableResolver getXPathVariableResolver(); /** * <p>Establish a function resolver.

* * <p>A NullPointerException is thrown if resolver is null.

* * @param resolver XPath function resolver. * * @throws NullPointerException If <code>resolver is null. */ public void setXPathFunctionResolver(XPathFunctionResolver resolver); /** * <p>Return the current function resolver.

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

* * @return Current function resolver. */ public XPathFunctionResolver getXPathFunctionResolver(); /** * <p>Establish a namespace context.

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

* * @param nsContext Namespace context to use. * * @throws NullPointerException If <code>nsContext is null. */ public void setNamespaceContext(NamespaceContext nsContext); /** * <p>Return the current namespace context.

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

* * @return Current Namespace context. */ public NamespaceContext getNamespaceContext(); /** * <p>Compile an XPath expression for later evaluation.

* * <p>If 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 expression contains any variables, the * {@link XPathVariableResolver} in effect * <strong>at compile time will be used to resolve them.

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

* * @param expression The XPath expression. * * @return Compiled XPath expression. * @throws XPathExpressionException If <code>expression cannot be compiled. * @throws NullPointerException If <code>expression is null. */ public XPathExpression compile(String expression) throws XPathExpressionException; /** * <p>Evaluate an XPath expression in the specified context and return the result as the specified type.

* * <p>See Evaluation of XPath Expressions for context item evaluation, * variable, function and <code>QName resolution and return type conversion.

* * <p>If 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}) * then an <code>IllegalArgumentException is thrown.

* * <p>If a null value is provided for * <code>item, an empty document will be used for the * context. * If <code>expression or returnType is null, then a * <code>NullPointerException is thrown.

* * @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 of returnType. * * @throws XPathExpressionException If <code>expression cannot be evaluated. * @throws IllegalArgumentException If <code>returnType is not one of the types defined in {@link XPathConstants}. * @throws NullPointerException If <code>expression or returnType is null. */ 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 String.

* * <p>This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a returnType of * {@link XPathConstants#STRING}.</p> * * <p>See Evaluation of XPath Expressions for context item evaluation, * variable, function and QName resolution and return type conversion.</p> * * <p>If a null value is provided for * <code>item, an empty document will be used for the * context. * If <code>expression is null, then a NullPointerException is thrown.

* * @param expression The XPath expression. * @param item The starting context (a node, for example). * * @return The <code>String that is the result of evaluating the expression and * converting the result to a <code>String. * * @throws XPathExpressionException If <code>expression cannot be evaluated. * @throws NullPointerException If <code>expression is null. */ public String evaluate(String expression, Object item) throws XPathExpressionException; /** * <p>Evaluate an XPath expression in the context of the specified InputSource * 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 Evaluation of XPath Expressions for context item evaluation, * variable, function and QName resolution and return type conversion.</p> * * <p>If returnType is not one of the types defined in {@link XPathConstants}, * then an <code>IllegalArgumentException is thrown.

* * <p>If expression, source or returnType is null, * then a <code>NullPointerException is thrown.

* * @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; /** * <p>Evaluate an XPath expression in the context of the specified 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 Evaluation of XPath Expressions for context item evaluation, * variable, function and QName resolution and return type conversion.</p> * * <p>If expression or source is null, * then a <code>NullPointerException is thrown.

* * @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 null. */ public String evaluate(String expression, InputSource source) throws XPathExpressionException; }

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Java example source code file (XPath.java)

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Java - Java tags/keywords

inputsource, namespacecontext, object, qname, sax, string, xpathexpressionexception, xpathfunctionresolver, xpathvariableresolver

The XPath.java Java example source code

/*
 * Copyright (c) 2003, 2005, 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 javax.xml.xpath;

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

/**
 * <p>XPath provides access to the XPath evaluation environment and expressions.

* * <a name="XPath-evaluation"/> * <table border="1" cellpadding="2"> * <thead> * <tr> * <th colspan="2">Evaluation of XPath Expressions. * </tr> * </thead> * <tbody> * <tr> * <td>context
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