Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (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.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.cocoon.xml.dom; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.LinkedList; import java.util.List; import java.util.ListIterator; import java.util.Map; import javax.xml.XMLConstants; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParserFactory; import org.apache.cocoon.util.location.Location; import org.apache.cocoon.util.location.LocationAttributes; import org.apache.cocoon.xml.SaxBuffer; import org.apache.commons.lang.BooleanUtils; import org.apache.excalibur.xml.sax.XMLizable; import org.w3c.dom.Attr; import org.w3c.dom.CDATASection; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.NamedNodeMap; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.w3c.dom.Text; import org.xml.sax.ContentHandler; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.SAXNotSupportedException; import org.xml.sax.XMLReader; /** * Helper class to create and retrieve information from DOM-trees. It provides * some functionality comparable to what's found in Avalon's Configuration * objects. These lasts one could however not be used by Cocoon Forms because they * don't provide an accurate model of an XML file (no mixed content, * no namespaced attributes, no namespace declarations, ...). * * <p>This class depends specifically on the Xerces DOM implementation to be * able to provide information about the location of elements in their source * XML file. See the {@link #getLocation(Element)} method. * @version $Id: DomHelper.java 587751 2007-10-24 02:41:36Z vgritsenko $ */ public class DomHelper { protected static final SAXParserFactory saxFactory = SAXParserFactory.newInstance(); static { saxFactory.setNamespaceAware(true); saxFactory.setValidating(false); } public static final String XMLNS_URI = XMLConstants.XMLNS_ATTRIBUTE_NS_URI; /** * Creates a W3C Document that remembers the location of each element in * the source file. The location of element nodes can then be retrieved * using the {@link #getLocation(Element)} method. * * @param inputSource the inputSource to read the document from */ public static Document parse(InputSource inputSource) throws SAXException, SAXNotSupportedException, IOException { try { final XMLReader parser = saxFactory.newSAXParser().getXMLReader(); final DOMBuilder builder = new DOMBuilder(); // Enhance the sax stream with location information final ContentHandler locationHandler = new LocationAttributes.Pipe(builder); parser.setContentHandler(locationHandler); parser.parse(inputSource); return builder.getDocument(); } catch (ParserConfigurationException pce) { throw new SAXException(pce); } } public static Location getLocationObject(Element element) { return LocationAttributes.getLocation(element); } /** * Retrieves the location of an element node in the source file from which * the Document was created. This will only work for Document's created * with the method {@link #parse(InputSource, ServiceManager)} of this class. */ public static String getLocation(Element element) { return LocationAttributes.getLocationString(element); } public static String getSystemIdLocation(Element element) { return LocationAttributes.getURI(element); } public static int getLineLocation(Element element) { return LocationAttributes.getLine(element); } public static int getColumnLocation(Element element) { return LocationAttributes.getColumn(element); } /** * Returns all Element children of an Element that belong to the given * namespace. */ public static Element[] getChildElements(Element element, String namespace) { ArrayList elements = new ArrayList(); NodeList nodeList = element.getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node instanceof Element && namespace.equals(node.getNamespaceURI())) elements.add(node); } return (Element[]) elements.toArray(new Element[elements.size()]); } /** * Returns all Element children of an Element that belong to the given * namespace and have the given local name. */ public static Element[] getChildElements(Element element, String namespace, String localName) { ArrayList elements = new ArrayList(); NodeList nodeList = element.getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node instanceof Element && namespace.equals(node.getNamespaceURI()) && localName.equals(node.getLocalName())) { elements.add(node); } } return (Element[]) elements.toArray(new Element[elements.size()]); } /** * Returns the first child element with the given namespace and localName, * or null if there is no such element. */ public static Element getChildElement(Element element, String namespace, String localName) { Element node = null; try { node = getChildElement(element, namespace, localName, false); } catch (Exception e) { node = null; } return node; } /** * Returns the first child element with the given namespace and localName, * or null if there is no such element and required flag is unset or * throws an Exception if the "required" flag is set. */ public static Element getChildElement(Element element, String namespace, String localName, boolean required) throws Exception { NodeList nodeList = element.getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node instanceof Element && namespace.equals(node.getNamespaceURI()) && localName.equals(node.getLocalName())) { return (Element) node; } } if (required) { throw new Exception("Missing element \"" + localName + "\" as child of element \"" + element.getTagName() + "\" at " + DomHelper.getLocation(element)); } else { return null; } } /** * Returns the value of an element's attribute, but throws an exception * if the element has no such attribute. */ public static String getAttribute(Element element, String attributeName) throws Exception { String attrValue = element.getAttribute(attributeName); if (attrValue.length() == 0) { throw new Exception("Missing attribute \"" + attributeName + "\" on element \"" + element.getTagName() + "\" at " + getLocation(element)); } return attrValue; } /** * Returns the value of an element's attribute, or a default value if the * element has no such attribute. */ public static String getAttribute(Element element, String attributeName, String defaultValue) { String attrValue = element.getAttribute(attributeName); if (attrValue.length() == 0) { return defaultValue; } return attrValue; } public static int getAttributeAsInteger(Element element, String attributeName) throws Exception { String attrValue = getAttribute(element, attributeName); try { return Integer.parseInt(attrValue); } catch (NumberFormatException e) { throw new Exception( "Cannot parse the value \"" + attrValue + "\" as an integer in the attribute \"" + attributeName + "\" on the element \"" + element.getTagName() + "\" at " + getLocation(element)); } } public static int getAttributeAsInteger(Element element, String attributeName, int defaultValue) throws Exception { String attrValue = element.getAttribute(attributeName); if (attrValue.length() == 0) { return defaultValue; } else { try { return Integer.parseInt(attrValue); } catch (NumberFormatException e) { throw new Exception("Cannot parse the value \"" + attrValue + "\" as an integer in the attribute \"" + attributeName + "\" on the element \"" + element.getTagName() + "\" at " + getLocation(element)); } } } public static boolean getAttributeAsBoolean(Element element, String attributeName, boolean defaultValue) { String attrValue = element.getAttribute(attributeName); Boolean result; try { result = BooleanUtils.toBooleanObject(attrValue, "true", "false", null); } catch (IllegalArgumentException iae) { result = null; } if (result != null) { return result.booleanValue(); } try { result = BooleanUtils.toBooleanObject(attrValue, "yes", "no", null); } catch (IllegalArgumentException iae) { result = null; } if (result != null) { return result.booleanValue(); } return defaultValue; } public static String getElementText(Element element) { StringBuffer value = new StringBuffer(); NodeList nodeList = element.getChildNodes(); for (int i = 0; i < nodeList.getLength(); i++) { Node node = nodeList.item(i); if (node instanceof Text || node instanceof CDATASection) { value.append(node.getNodeValue()); } } return value.toString(); } /** * Returns the content of the given Element as an object implementing the * XMLizable interface. Practically speaking, the implementation uses the * {@link SaxBuffer} class. The XMLizable object will be a standalone blurb * of SAX events, not producing start/endDocument calls and containing all * necessary namespace declarations. */ public static XMLizable compileElementContent(Element element) { // Remove location information LocationAttributes.remove(element, true); SaxBuffer saxBuffer = new SaxBuffer(); DOMStreamer domStreamer = new DOMStreamer(); domStreamer.setContentHandler(saxBuffer); NodeList childNodes = element.getChildNodes(); for (int i = 0; i < childNodes.getLength(); i++) { try { domStreamer.stream(childNodes.item(i)); } catch (SAXException e) { // It's unlikely that an exception will occur here, // so use a runtime exception throw new RuntimeException("Error in DomHelper.compileElementContent: " + e.toString()); } } return saxBuffer; } public static Map getLocalNSDeclarations(Element elm) { return addLocalNSDeclarations(elm, null); } private static Map addLocalNSDeclarations(Element elm, Map nsDeclarations) { NamedNodeMap atts = elm.getAttributes(); int attsSize = atts.getLength(); for (int i = 0; i < attsSize; i++) { Attr attr = (Attr) atts.item(i); if (XMLNS_URI.equals(attr.getNamespaceURI())) { String nsUri = attr.getValue(); String pfx = attr.getLocalName(); if (nsDeclarations == null) nsDeclarations = new HashMap(); nsDeclarations.put(nsUri, pfx); } } return nsDeclarations; } public static Map getInheritedNSDeclarations(Element elm) { List ancestorsAndSelf = new LinkedList(); Element current = elm; while (current != null) { ancestorsAndSelf.add(current); Node parent = current.getParentNode(); if (parent.getNodeType() == Node.ELEMENT_NODE) current = (Element) parent; else current = null; } Map nsDeclarations = null; ListIterator iter = ancestorsAndSelf.listIterator(ancestorsAndSelf.size()); while (iter.hasPrevious()) { Element element = (Element) iter.previous(); nsDeclarations = addLocalNSDeclarations(element, nsDeclarations); } return nsDeclarations; } }