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.commons.configuration; import java.io.File; import java.io.PrintWriter; import java.io.Reader; import java.io.Writer; import java.net.URL; import java.util.Iterator; import java.util.List; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import org.apache.commons.lang.StringEscapeUtils; import org.apache.commons.lang.StringUtils; import org.xml.sax.Attributes; import org.xml.sax.EntityResolver; import org.xml.sax.InputSource; import org.xml.sax.XMLReader; import org.xml.sax.helpers.DefaultHandler; /** * This configuration implements the XML properties format introduced in Java * 5.0, see http://java.sun.com/j2se/1.5.0/docs/api/java/util/Properties.html. * An XML properties file looks like this: * * <pre> * <?xml version="1.0"?> * <!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd"> * <properties> * <comment>Description of the property list</comment> * <entry key="key1">value1</entry> * <entry key="key2">value2</entry> * <entry key="key3">value3</entry> * </properties> * </pre> * * The Java 5.0 runtime is not required to use this class. The default encoding * for this configuration format is UTF-8. Note that unlike * <code>PropertiesConfiguration</code>, <code>XMLPropertiesConfiguration</code> * does not support includes. * * <em>Note:</em>Configuration objects of this type can be read concurrently * by multiple threads. However if one of these threads modifies the object, * synchronization has to be performed manually. * * @author Emmanuel Bourg * @author Alistair Young * @version $Revision: 548098 $, $Date: 2007-06-17 21:34:03 +0200 (So, 17 Jun 2007) $ * @since 1.1 */ public class XMLPropertiesConfiguration extends PropertiesConfiguration { /** * The default encoding (UTF-8 as specified by http://java.sun.com/j2se/1.5.0/docs/api/java/util/Properties.html) */ private static final String DEFAULT_ENCODING = "UTF-8"; // initialization block to set the encoding before loading the file in the constructors { setEncoding(DEFAULT_ENCODING); } /** * Creates an empty XMLPropertyConfiguration object which can be * used to synthesize a new Properties file by adding values and * then saving(). An object constructed by this C'tor can not be * tickled into loading included files because it cannot supply a * base for relative includes. */ public XMLPropertiesConfiguration() { super(); } /** * Creates and loads the xml properties from the specified file. * The specified file can contain "include" properties which then * are loaded and merged into the properties. * * @param fileName The name of the properties file to load. * @throws ConfigurationException Error while loading the properties file */ public XMLPropertiesConfiguration(String fileName) throws ConfigurationException { super(fileName); } /** * Creates and loads the xml properties from the specified file. * The specified file can contain "include" properties which then * are loaded and merged into the properties. * * @param file The properties file to load. * @throws ConfigurationException Error while loading the properties file */ public XMLPropertiesConfiguration(File file) throws ConfigurationException { super(file); } /** * Creates and loads the xml properties from the specified URL. * The specified file can contain "include" properties which then * are loaded and merged into the properties. * * @param url The location of the properties file to load. * @throws ConfigurationException Error while loading the properties file */ public XMLPropertiesConfiguration(URL url) throws ConfigurationException { super(url); } public void load(Reader in) throws ConfigurationException { SAXParserFactory factory = SAXParserFactory.newInstance(); factory.setNamespaceAware(false); factory.setValidating(true); try { SAXParser parser = factory.newSAXParser(); XMLReader xmlReader = parser.getXMLReader(); xmlReader.setEntityResolver(new EntityResolver() { public InputSource resolveEntity(String publicId, String systemId) { return new InputSource(getClass().getClassLoader().getResourceAsStream("properties.dtd")); } }); xmlReader.setContentHandler(new XMLPropertiesHandler()); xmlReader.parse(new InputSource(in)); } catch (Exception e) { throw new ConfigurationException("Unable to parse the configuration file", e); } // todo: support included properties ? } public void save(Writer out) throws ConfigurationException { PrintWriter writer = new PrintWriter(out); String encoding = getEncoding() != null ? getEncoding() : DEFAULT_ENCODING; writer.println("<?xml version=\"1.0\" encoding=\"" + encoding + "\"?>"); writer.println("<!DOCTYPE properties SYSTEM \"http://java.sun.com/dtd/properties.dtd\">"); writer.println("<properties>"); if (getHeader() != null) { writer.println(" <comment>" + StringEscapeUtils.escapeXml(getHeader()) + "</comment>"); } Iterator keys = getKeys(); while (keys.hasNext()) { String key = (String) keys.next(); Object value = getProperty(key); if (value instanceof List) { writeProperty(writer, key, (List) value); } else { writeProperty(writer, key, value); } } writer.println("</properties>"); writer.flush(); } /** * Write a property. * * @param out the output stream * @param key the key of the property * @param value the value of the property */ private void writeProperty(PrintWriter out, String key, Object value) { // escape the key String k = StringEscapeUtils.escapeXml(key); if (value != null) { // escape the value String v = StringEscapeUtils.escapeXml(String.valueOf(value)); v = StringUtils.replace(v, String.valueOf(getListDelimiter()), "\\" + getListDelimiter()); out.println(" <entry key=\"" + k + "\">" + v + "</entry>"); } else { out.println(" <entry key=\"" + k + "\"/>"); } } /** * Write a list property. * * @param out the output stream * @param key the key of the property * @param values a list with all property values */ private void writeProperty(PrintWriter out, String key, List values) { for (int i = 0; i < values.size(); i++) { writeProperty(out, key, values.get(i)); } } /** * SAX Handler to parse a XML properties file. * * @author Alistair Young * @since 1.2 */ private class XMLPropertiesHandler extends DefaultHandler { /** The key of the current entry being parsed. */ private String key; /** The value of the current entry being parsed. */ private StringBuffer value = new StringBuffer(); /** Indicates that a comment is being parsed. */ private boolean inCommentElement; /** Indicates that an entry is being parsed. */ private boolean inEntryElement; public void startElement(String uri, String localName, String qName, Attributes attrs) { if ("comment".equals(qName)) { inCommentElement = true; } if ("entry".equals(qName)) { key = attrs.getValue("key"); inEntryElement = true; } } public void endElement(String uri, String localName, String qName) { if (inCommentElement) { // We've just finished a <comment> element so set the header setHeader(value.toString()); inCommentElement = false; } if (inEntryElement) { // We've just finished an <entry> element, so add the key/value pair addProperty(key, value.toString()); inEntryElement = false; } // Clear the element value buffer value = new StringBuffer(); } public void characters(char[] chars, int start, int length) { /** * We're currently processing an element. All character data from now until * the next endElement() call will be the data for this element. */ value.append(chars, start, length); } } }