Java tutorial
/* * Copyright 1999-2004 The Apache Software Foundation. * * Licensed 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.woody.util; import java.io.IOException; import java.util.ArrayList; import org.apache.cocoon.xml.SaxBuffer; import org.apache.cocoon.xml.dom.DOMStreamer; import org.apache.commons.lang.BooleanUtils; import org.apache.excalibur.xml.sax.XMLizable; import org.apache.xerces.dom.NodeImpl; import org.apache.xerces.parsers.DOMParser; import org.apache.xerces.xni.Augmentations; import org.apache.xerces.xni.NamespaceContext; import org.apache.xerces.xni.QName; import org.apache.xerces.xni.XMLAttributes; import org.apache.xerces.xni.XMLLocator; import org.apache.xerces.xni.XNIException; import org.w3c.dom.CDATASection; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.w3c.dom.Text; import org.w3c.dom.UserDataHandler; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.SAXNotSupportedException; /** * 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 Woody 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 CVS $Id: DomHelper.java 360378 2005-12-31 18:10:07Z antonio $ */ public class DomHelper { /** * 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)} of this class. */ public static String getLocation(Element element) { String location = null; if (element instanceof NodeImpl) { location = (String) ((NodeImpl) element).getUserData("location"); } if (location != null) { return location; } return "(location unknown)"; } public static String getSystemIdLocation(Element element) { String loc = getLocation(element); if (loc.charAt(0) != '(') { int end = loc.lastIndexOf(':'); if (end > 0) { int start = loc.lastIndexOf(':', end - 1); if (start >= 0) { return loc.substring(0, start); } } } return null; } public static int getLineLocation(Element element) { String loc = getLocation(element); if (loc.charAt(0) != '(') { int end = loc.lastIndexOf(':'); if (end > 0) { int start = loc.lastIndexOf(':', end - 1); if (start >= 0) { return Integer.parseInt(loc.substring(start + 1, end)); } } } return -1; } public static int getColumnLocation(Element element) { String loc = getLocation(element); if (loc.charAt(0) != '(') { int end = loc.lastIndexOf(':'); if (end > 0) { return Integer.parseInt(loc.substring(end)); } } return -1; } /** * 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[0]); } /** * 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[0]); } /** * 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) throws Exception { 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) { 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; } /** * 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. */ public static Document parse(InputSource inputSource) throws SAXException, SAXNotSupportedException, IOException { DOMParser domParser = new LocationTrackingDOMParser(); domParser.setFeature("http://apache.org/xml/features/dom/defer-node-expansion", false); domParser.setFeature("http://apache.org/xml/features/dom/create-entity-ref-nodes", false); domParser.parse(inputSource); return domParser.getDocument(); } /** * An extension of the Xerces DOM parser that puts the location of each * node in that node's UserData. */ public static class LocationTrackingDOMParser extends DOMParser { XMLLocator locator; public void startDocument(XMLLocator xmlLocator, String s, NamespaceContext namespaceContext, Augmentations augmentations) throws XNIException { super.startDocument(xmlLocator, s, namespaceContext, augmentations); this.locator = xmlLocator; setLocation(); } public void startElement(QName qName, XMLAttributes xmlAttributes, Augmentations augmentations) throws XNIException { super.startElement(qName, xmlAttributes, augmentations); setLocation(); } private final void setLocation() { // Older versions of Xerces had a different signature for the // startDocument method. If such a version is used, the // startDocument method above will not be called and locator will // hence be null. // Tell the users this so that they don't get a stupid NPE. if (this.locator == null) { throw new RuntimeException("Error: locator is null. Check that you have the" + " correct version of Xerces (such as the one that" + " comes with Cocoon) in your endorsed library path."); } NodeImpl node = null; try { node = (NodeImpl) this.getProperty("http://apache.org/xml/properties/dom/current-element-node"); } catch (org.xml.sax.SAXException ex) { System.err.println("except" + ex); } if (node != null) { String location = locator.getLiteralSystemId() + ":" + locator.getLineNumber() + ":" + locator.getColumnNumber(); node.setUserData("location", location, (UserDataHandler) null); } } } }