Java tutorial
/* * This file is part of the Echo Web Application Framework (hereinafter "Echo"). * Copyright (C) 2002-2009 NextApp, Inc. * * Version: MPL 1.1/GPL 2.0/LGPL 2.1 * * The contents of this file are subject to the Mozilla Public License Version * 1.1 (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * http://www.mozilla.org/MPL/ * * Software distributed under the License is distributed on an "AS IS" basis, * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License * for the specific language governing rights and limitations under the * License. * * Alternatively, the contents of this file may be used under the terms of * either the GNU General Public License Version 2 or later (the "GPL"), or * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), * in which case the provisions of the GPL or the LGPL are applicable instead * of those above. If you wish to allow use of your version of this file only * under the terms of either the GPL or the LGPL, and not to allow others to * use your version of this file under the terms of the MPL, indicate your * decision by deleting the provisions above and replace them with the notice * and other provisions required by the GPL or the LGPL. If you do not delete * the provisions above, a recipient may use your version of this file under * the terms of any one of the MPL, the GPL or the LGPL. */ import java.io.IOException; import java.io.OutputStream; import java.io.PrintWriter; import java.util.ArrayList; import java.util.List; import java.util.Properties; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.transform.OutputKeys; import javax.xml.transform.Transformer; import javax.xml.transform.TransformerException; import javax.xml.transform.TransformerFactory; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamResult; import org.w3c.dom.DOMImplementation; import org.w3c.dom.Document; import org.w3c.dom.DocumentType; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.w3c.dom.Text; import org.xml.sax.EntityResolver; import org.xml.sax.InputSource; import org.xml.sax.SAXException; /** * A utility class which provides methods for working with a W3C DOM. */ public class DomUtil { public static final Properties OUTPUT_PROPERTIES_INDENT; static { OUTPUT_PROPERTIES_INDENT = new Properties(); OUTPUT_PROPERTIES_INDENT.setProperty(OutputKeys.INDENT, "yes"); OUTPUT_PROPERTIES_INDENT.setProperty("{http://xml.apache.org/xalan}indent-amount", "4"); } /** * Entity resolver which throws a SAXException when invoked to avoid external entity injection. */ private static final EntityResolver entityResolver = new EntityResolver() { /** * @see org.xml.sax.EntityResolver#resolveEntity(java.lang.String, java.lang.String) */ public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException { throw new SAXException("External entities not supported."); } }; /** * ThreadLocal cache of <code>DocumentBuilder</code> instances. */ private static final ThreadLocal documentBuilders = new ThreadLocal() { /** * @see java.lang.ThreadLocal#initialValue() */ protected Object initialValue() { try { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); factory.setNamespaceAware(true); DocumentBuilder builder = factory.newDocumentBuilder(); builder.setEntityResolver(entityResolver); return builder; } catch (ParserConfigurationException ex) { throw new RuntimeException(ex); } } }; /** * ThreadLocal cache of <code>TransformerFactory</code> instances. */ private static final ThreadLocal transformerFactories = new ThreadLocal() { /** * @see java.lang.ThreadLocal#initialValue() */ protected Object initialValue() { TransformerFactory factory = TransformerFactory.newInstance(); return factory; } }; /** * Creates a new document. * * @param qualifiedName the qualified name of the document type to be * created * @param publicId the external subset public identifier * @param systemId the external subset system identifier * @param namespaceUri the namespace URI of the document element to create */ public static Document createDocument(String qualifiedName, String publicId, String systemId, String namespaceUri) { DOMImplementation dom = DomUtil.getDocumentBuilder().getDOMImplementation(); DocumentType docType = dom.createDocumentType(qualifiedName, publicId, systemId); Document document = dom.createDocument(namespaceUri, qualifiedName, docType); if (namespaceUri != null) { document.getDocumentElement().setAttribute("xmlns", namespaceUri); } return document; } /** * Retrieves a thread-specific <code>DocumentBuilder</code>. * As it is a shared resource, the returned object should not be reconfigured in any fashion. * * @return the <code>DocumentBuilder</code> serving the current thread. */ public static DocumentBuilder getDocumentBuilder() { return (DocumentBuilder) documentBuilders.get(); } /** * Retrieves a thread-specific <code>TransformerFactory</code>. * As it is a shared resource, the returned object should not be reconfigured in any fashion. * * @return the <code>TransformerFactory</code> serving the current thread. */ public static TransformerFactory getTransformerFactory() { return (TransformerFactory) transformerFactories.get(); } /** * Determines whether a specific boolean flag is set on an element. * * @param element The element to analyze. * @param attributeName The name of the boolean 'flag' attribute. * @return True if the value of the attribute is 'true', false if it is * not or if the attribute does not exist. */ public static boolean getBooleanAttribute(Element element, String attributeName) { String value = element.getAttribute(attributeName); if (value == null) { return false; } else if (value.equals("true")) { return true; } else { return false; } } /** * Retrieves the first immediate child element of the specified element * whose name matches the provided <code>name</code> parameter. * * @param parentElement The element to search. * @param name The name of the child element. * @return The child element, or null if none was found. */ public static Element getChildElementByTagName(Element parentElement, String name) { NodeList nodes = parentElement.getChildNodes(); int length = nodes.getLength(); for (int index = 0; index < length; ++index) { if (nodes.item(index).getNodeType() == Node.ELEMENT_NODE && name.equals(nodes.item(index).getNodeName())) { return (Element) nodes.item(index); } } return null; } /** * Retrieves all immediate child elements of the specified element whose * names match the provided <code>name</code> parameter. * * @param parentElement The element to search. * @param name The name of the child element. * @return An array of matching child elements. */ public static Element[] getChildElementsByTagName(Element parentElement, String name) { List children = new ArrayList(); NodeList nodes = parentElement.getChildNodes(); int length = nodes.getLength(); for (int index = 0; index < length; ++index) { if (nodes.item(index).getNodeType() == Node.ELEMENT_NODE && name.equals(nodes.item(index).getNodeName())) { children.add(nodes.item(index)); } } Element[] childElements = new Element[children.size()]; return (Element[]) children.toArray(childElements); } /** * Counts the number of immediate child elements of the specified element * whose names match the provided <code>name</code> parameter. * * @param parentElement The element to analyze. * @param name The name of the child element. * @return The number of matching child elements. */ public static int getChildElementCountByTagName(Element parentElement, String name) { NodeList nodes = parentElement.getChildNodes(); int length = nodes.getLength(); int count = 0; for (int index = 0; index < length; ++index) { if (nodes.item(index).getNodeType() == Node.ELEMENT_NODE && name.equals(nodes.item(index).getNodeName())) { ++count; } } return count; } /** * Returns the text content of a DOM <code>Element</code>. * * @param element The <code>Element</code> to analyze. */ public static String getElementText(Element element) { NodeList children = element.getChildNodes(); int childCount = children.getLength(); for (int index = 0; index < childCount; ++index) { if (children.item(index) instanceof Text) { Text text = (Text) children.item(index); return text.getData(); } } return null; } /** * Writes the <code>Document</code> to the specified <code>OutputStream</code>. * * @param document the <code>Document</code> * @param out the <code>OutputStream</code> * @param outputProperties output properties passed to XML transformer * @throws SAXException */ public static void save(Document document, OutputStream out, Properties outputProperties) throws SAXException { saveImpl(document, new StreamResult(out), outputProperties); } /** * Writes the <code>Document</code> to the specified <code>PrintWriter</code>. * * @param document the <code>Document</code> * @param w the <code>PrintWriter</code> * @param outputProperties output properties passed to XML transformer * @throws SAXException */ public static void save(Document document, PrintWriter w, Properties outputProperties) throws SAXException { saveImpl(document, new StreamResult(w), outputProperties); } /** * Work method for public save() methods. */ private static void saveImpl(Document document, StreamResult output, Properties outputProperties) throws SAXException { try { TransformerFactory tFactory = getTransformerFactory(); Transformer transformer = tFactory.newTransformer(); if (outputProperties != null) { transformer.setOutputProperties(outputProperties); } DOMSource source = new DOMSource(document); transformer.transform(source, output); } catch (TransformerException ex) { throw new SAXException("Unable to write document to OutputStream.", ex); } } /** * Sets the text content of a DOM <code>Element</code>. * * @param element The <code>Element</code> to modify. * @param value The new text value. */ public static void setElementText(Element element, String value) { NodeList children = element.getChildNodes(); int childCount = children.getLength(); for (int index = 0; index < childCount; ++index) { if (children.item(index) instanceof Text) { Text text = (Text) children.item(index); text.setData(value); return; } } Text text = element.getOwnerDocument().createTextNode(value); element.appendChild(text); } /** Non-instantiable class. */ private DomUtil() { } }