Java tutorial
package job.tot.xml; /* ==================================================================== * The Apache Software License, Version 1.1 * * Copyright (c) 2002-2003 The Apache Software Foundation. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. The end-user documentation included with the redistribution, if * any, must include the following acknowledgement: * "This product includes software developed by the * Apache Software Foundation (http://www.apache.org/)." * Alternately, this acknowledgement may appear in the software itself, * if and wherever such third-party acknowledgements normally appear. * * 4. The names "The Jakarta Project", "Commons", and "Apache Software * Foundation" must not be used to endorse or promote products derived * from this software without prior written permission. For written * permission, please contact apache@apache.org. * * 5. Products derived from this software may not be called "Apache" * nor may "Apache" appear in their names without prior written * permission of the Apache Software Foundation. * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * ==================================================================== * * This software consists of voluntary contributions made by many * individuals on behalf of the Apache Software Foundation. For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. */ import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.net.URL; import java.util.Iterator; import java.util.List; import org.dom4j.Attribute; import org.dom4j.Document; import org.dom4j.Element; import org.dom4j.io.OutputFormat; import org.dom4j.io.SAXReader; import org.dom4j.io.XMLWriter; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang.exception.NestableRuntimeException; /** * Reads a XML configuration file. * * To retrieve the value of an attribute of an element, use * <code>X.Y.Z[@attribute]</code>. The '@' symbol was chosen for * consistency with XPath. * * Setting property values will <b>NOT</b> automatically persist * changes to disk, unless <code>autoSave=true</code>. * * @author <a href="mailto:kelvint@apache.org">Kelvin Tan</a> * @author <a href="mailto:dlr@apache.org">Daniel Rall</a> * @since 0.8.1 */ public class DOM4JConfiguration extends XMLConfiguration { // For conformance with xpath private static final char ATTRIB_MARKER = '@'; private static final String ATTRIB_START_MARKER = "[" + ATTRIB_MARKER; /** * For consistency with properties files. Access nodes via an * "A.B.C" notation. */ private static final String NODE_DELIMITER = "."; /** * A handle to our data source. */ private String fileName; /** * The XML document from our data source. */ private Document document; /** * If true, modifications are immediately persisted. */ private boolean autoSave = false; /** * Empty construtor. You must provide a file/fileName * and call the load method * */ public DOM4JConfiguration() { } /** * Attempts to load the XML file as a resource from the * classpath. The XML file must be located somewhere in the * classpath. * * @param resource Name of the resource * @exception Exception If error reading data source. * @see DOM4JConfiguration#DOM4JConfiguration(File) */ public DOM4JConfiguration(String resource) throws Exception { setFile(resourceURLToFile(resource)); load(); } /** * Attempts to load the XML file. * * @param file File object representing the XML file. * @exception Exception If error reading data source. */ public DOM4JConfiguration(File file) throws Exception { setFile(file); load(); } public void load() throws Exception { document = new SAXReader().read(ConfigurationUtils.getURL(getBasePath(), getFileName())); initProperties(document.getRootElement(), new StringBuffer()); } private static File resourceURLToFile(String resource) { URL confURL = DOM4JConfiguration.class.getClassLoader().getResource(resource); if (confURL == null) { confURL = ClassLoader.getSystemResource(resource); } return new File(confURL.getFile()); } /** * Loads and initializes from the XML file. * * @param element The element to start processing from. Callers * should supply the root element of the document. * @param hierarchy */ private void initProperties(Element element, StringBuffer hierarchy) { for (Iterator it = element.elementIterator(); it.hasNext();) { StringBuffer subhierarchy = new StringBuffer(hierarchy.toString()); Element child = (Element) it.next(); String nodeName = child.getName(); String nodeValue = child.getTextTrim(); subhierarchy.append(nodeName); if (nodeValue.length() > 0) { super.addProperty(subhierarchy.toString(), nodeValue); } // Add attributes as x.y{ATTRIB_START_MARKER}att{ATTRIB_END_MARKER} List attributes = child.attributes(); for (int j = 0, k = attributes.size(); j < k; j++) { Attribute a = (Attribute) attributes.get(j); String attName = subhierarchy.toString() + '[' + ATTRIB_MARKER + a.getName() + ']'; String attValue = a.getValue(); super.addProperty(attName, attValue); } StringBuffer buf = new StringBuffer(subhierarchy.toString()); initProperties(child, buf.append('.')); } } /** * Calls super method, and also ensures the underlying {@link * Document} is modified so changes are persisted when saved. * * @param name * @param value */ public void addProperty(String name, Object value) { super.addProperty(name, value); setXmlProperty(name, value); possiblySave(); } /** * Calls super method, and also ensures the underlying {@link * Document} is modified so changes are persisted when saved. * * @param name * @param value */ public void setProperty(String name, Object value) { super.setProperty(name, value); setXmlProperty(name, value); possiblySave(); } /** * Sets the property value in our document tree, auto-saving if * appropriate. * * @param name The name of the element to set a value for. * @param value The value to set. */ private void setXmlProperty(String name, Object value) { String[] nodes = StringUtils.split(name, NODE_DELIMITER); String attName = null; Element element = document.getRootElement(); for (int i = 0; i < nodes.length; i++) { String eName = nodes[i]; int index = eName.indexOf(ATTRIB_START_MARKER); if (index > -1) { attName = eName.substring(index + ATTRIB_START_MARKER.length(), eName.length() - 1); eName = eName.substring(0, index); } // If we don't find this part of the property in the XML heirarchy // we add it as a new node if (element.element(eName) == null && attName == null) { element.addElement(eName); } element = element.element(eName); } if (attName == null) { element.setText((String) value); } else { element.addAttribute(attName, (String) value); } } /** * Calls super method, and also ensures the underlying {@link * Document} is modified so changes are persisted when saved. * * @param name The name of the property to clear. */ public void clearProperty(String name) { super.clearProperty(name); clearXmlProperty(name); possiblySave(); } private void clearXmlProperty(String name) { String[] nodes = StringUtils.split(name, NODE_DELIMITER); String attName = null; Element element = document.getRootElement(); for (int i = 0; i < nodes.length; i++) { String eName = nodes[i]; int index = eName.indexOf(ATTRIB_START_MARKER); if (index > -1) { attName = eName.substring(index + ATTRIB_START_MARKER.length(), eName.length() - 1); eName = eName.substring(0, index); } element = element.element(eName); if (element == null) { return; } } if (attName == null) { element.remove(element.element(nodes[nodes.length - 1])); } else { element.remove(element.attribute(attName)); } } /** */ private void possiblySave() { if (autoSave) { try { save(); } catch (IOException e) { throw new NestableRuntimeException("Failed to auto-save", e); } } } /** * If true, changes are automatically persisted. * @param autoSave */ public void setAutoSave(boolean autoSave) { this.autoSave = autoSave; } public synchronized void save() throws IOException { XMLWriter writer = null; OutputStream out = null; try { OutputFormat outputter = OutputFormat.createPrettyPrint(); out = new BufferedOutputStream(new FileOutputStream(getFile())); writer = new XMLWriter(out, outputter); writer.write(document); } finally { if (out != null) { out.close(); } if (writer != null) { writer.close(); } } } /** * Returns the file. * @return File */ public File getFile() { return ConfigurationUtils.constructFile(getBasePath(), getFileName()); } /** * Sets the file. * @param file The file to set */ public void setFile(File file) { this.fileName = file.getAbsolutePath(); } public void setFileName(String fileName) { this.fileName = fileName; } /** * Returns the fileName. * @return String */ public String getFileName() { return fileName; } }