* <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}. * 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}. * 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. * </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 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 * method is invoked, applications may not recursively call * the <code>evaluate method. * <p> * * @author <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor * @see <a href="http://www.w3.org/TR/xpath#section-Expressions">XML Path Language (XPath) Version 1.0, Expressions * @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>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 a null value is provided for * <code>item, an empty document will be used for the * context. * If <code>returnType is null, then a NullPointerException is thrown.

* * @param item The starting context (a node, for example). * @param returnType The desired return type. * * @return The <code>Object that is the result of evaluating the expression and converting the result to * <code>returnType. * * @throws XPathExpressionException If the expression cannot be evaluated. * @throws IllegalArgumentException If <code>returnType is not one of the types defined in {@link XPathConstants}. * @throws NullPointerException If <code>returnType is null. */ 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 String.

* * <p>This method calls {@link #evaluate(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. * * @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 the expression cannot be evaluated. */ public String evaluate(Object item) throws XPathExpressionException; /** * <p>Evaluate the compiled 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(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 source or returnType is null, * then a <code>NullPointerException is thrown.

* * @param source The <code>InputSource of the document to evaluate over. * @param returnType The desired return type. * * @return The <code>Object that is the result of evaluating the expression and converting the result to * <code>returnType. * * @throws XPathExpressionException If the expression cannot be evaluated. * @throws IllegalArgumentException If <code>returnType is not one of the types defined in {@link XPathConstants}. * @throws NullPointerException If <code>source or returnType is null. */ public Object evaluate(InputSource source, QName returnType) throws XPathExpressionException; /** * <p>Evaluate the compiled XPath expression in the context of the specified InputSource and return the result as a * <code>String.

* * <p>This method calls {@link #evaluate(InputSource source, 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 source is null, then a NullPointerException is thrown.

* * @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 the expression cannot be evaluated. * @throws NullPointerException If <code>source is null. */ public String evaluate(InputSource source) throws XPathExpressionException; }

Java example source code file (XPathExpression.java) This example Java source code file (XPathExpression.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM. Learn more about this Java project at its project page. Java - Java tags/keywords object, qname, sax, string, xpathexpressionexception The XPathExpression.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; /** * <p>XPathExpression provides access to compiled XPath expressions. * * <a name="XPathExpression-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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