A utility class which provides methods for working with a W3C DOM
/*
* 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"),
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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() { }
}
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