Java tutorial
/** * $RCSfile$ * $Revision$ * $Date$ * * Copyright (C) 2004-2008 Jive Software. All rights reserved. * * This software is published under the terms of the GNU Public License (GPL), * a copy of which is included in this distribution, or a commercial license * agreement with Jive. */ package com.weibo.wesync.notify.xml; import org.dom4j.CDATA; import org.dom4j.Document; import org.dom4j.Element; import org.dom4j.Node; import org.dom4j.io.OutputFormat; import org.dom4j.io.SAXReader; import org.dom4j.io.XMLWriter; import org.apache.commons.lang.StringEscapeUtils; import java.io.*; import java.util.*; /** * Provides the the ability to use simple XML property files. Each property is * in the form X.Y.Z, which would map to an XML snippet of: * <pre> * <X> * <Y> * <Z>someValue</Z> * </Y> * </X> * </pre> * <p/> * The XML file is passed in to the constructor and must be readable and * writtable. Setting property values will automatically persist those value * to disk. The file encoding used is UTF-8. * * @author Derek DeMoro * @author Iain Shigeoka */ public class XMLProperties { private File file; private Document document; /** * Parsing the XML file every time we need a property is slow. Therefore, * we use a Map to cache property values that are accessed more than once. */ private Map<String, String> propertyCache = new HashMap<String, String>(); /** * Creates a new XMLPropertiesTest object. * * @param fileName the full path the file that properties should be read from * and written to. * @throws IOException if an error occurs loading the properties. */ public XMLProperties(String fileName) throws IOException { this(new File(fileName)); } /** * Loads XML properties from a stream. * * @param in the input stream of XML. * @throws IOException if an exception occurs when reading the stream. */ public XMLProperties(InputStream in) throws IOException { Reader reader = new BufferedReader(new InputStreamReader(in)); buildDoc(reader); } /** * Creates a new XMLPropertiesTest object. * * @param file the file that properties should be read from and written to. * @throws IOException if an error occurs loading the properties. */ public XMLProperties(File file) throws IOException { this.file = file; if (!file.exists()) { // Attempt to recover from this error case by seeing if the // tmp file exists. It's possible that the rename of the // tmp file failed the last time Jive was running, // but that it exists now. File tempFile; tempFile = new File(file.getParentFile(), file.getName() + ".tmp"); if (tempFile.exists()) { tempFile.renameTo(file); } // There isn't a possible way to recover from the file not // being there, so throw an error. else { throw new FileNotFoundException("XML properties file does not exist: " + file.getName()); } } // Check read and write privs. if (!file.canRead()) { throw new IOException("XML properties file must be readable: " + file.getName()); } if (!file.canWrite()) { throw new IOException("XML properties file must be writable: " + file.getName()); } FileReader reader = new FileReader(file); buildDoc(reader); } /** * Returns the value of the specified property. * * @param name the name of the property to get. * @return the value of the specified property. */ public synchronized String getProperty(String name) { String value = propertyCache.get(name); if (value != null) { return value; } String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy. Element element = document.getRootElement(); for (String aPropName : propName) { element = element.element(aPropName); if (element == null) { // This node doesn't match this part of the property name which // indicates this property doesn't exist so return null. return null; } } // At this point, we found a matching property, so return its value. // Empty strings are returned as null. value = element.getTextTrim(); if ("".equals(value)) { return null; } else { // Add to cache so that getting property next time is fast. propertyCache.put(name, value); return value; } } /** * Return all values who's path matches the given property * name as a String array, or an empty array if the if there * are no children. This allows you to retrieve several values * with the same property name. For example, consider the * XML file entry: * <pre> * <foo> * <bar> * <prop>some value</prop> * <prop>other value</prop> * <prop>last value</prop> * </bar> * </foo> * </pre> * If you call getProperties("foo.bar.prop") will return a string array containing * {"some value", "other value", "last value"}. * * @param name the name of the property to retrieve * @return all child property values for the given node name. */ public String[] getProperties(String name) { String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy, // stopping one short. Element element = document.getRootElement(); for (int i = 0; i < propName.length - 1; i++) { element = element.element(propName[i]); if (element == null) { // This node doesn't match this part of the property name which // indicates this property doesn't exist so return empty array. return new String[] {}; } } // We found matching property, return names of children. Iterator iter = element.elementIterator(propName[propName.length - 1]); List<String> props = new ArrayList<String>(); String value; while (iter.hasNext()) { // Empty strings are skipped. value = ((Element) iter.next()).getTextTrim(); if (!"".equals(value)) { props.add(value); } } String[] childrenNames = new String[props.size()]; return props.toArray(childrenNames); } /** * Return all values who's path matches the given property * name as a String array, or an empty array if the if there * are no children. This allows you to retrieve several values * with the same property name. For example, consider the * XML file entry: * <pre> * <foo> * <bar> * <prop>some value</prop> * <prop>other value</prop> * <prop>last value</prop> * </bar> * </foo> * </pre> * If you call getProperties("foo.bar.prop") will return a string array containing * {"some value", "other value", "last value"}. * * @param name the name of the property to retrieve * @return all child property values for the given node name. */ public Iterator getChildProperties(String name) { String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy, // stopping one short. Element element = document.getRootElement(); for (int i = 0; i < propName.length - 1; i++) { element = element.element(propName[i]); if (element == null) { // This node doesn't match this part of the property name which // indicates this property doesn't exist so return empty array. return Collections.EMPTY_LIST.iterator(); } } // We found matching property, return values of the children. Iterator iter = element.elementIterator(propName[propName.length - 1]); ArrayList<String> props = new ArrayList<String>(); while (iter.hasNext()) { props.add(((Element) iter.next()).getText()); } return props.iterator(); } /** * Returns the value of the attribute of the given property name or <tt>null</tt> * if it doesn't exist. Note, this * * @param name the property name to lookup - ie, "foo.bar" * @param attribute the name of the attribute, ie "id" * @return the value of the attribute of the given property or <tt>null</tt> if * it doesn't exist. */ public String getAttribute(String name, String attribute) { if (name == null || attribute == null) { return null; } String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy. Element element = document.getRootElement(); for (String child : propName) { element = element.element(child); if (element == null) { // This node doesn't match this part of the property name which // indicates this property doesn't exist so return empty array. break; } } if (element != null) { // Get its attribute values return element.attributeValue(attribute); } return null; } /** * Sets a property to an array of values. Multiple values matching the same property * is mapped to an XML file as multiple elements containing each value. * For example, using the name "foo.bar.prop", and the value string array containing * {"some value", "other value", "last value"} would produce the following XML: * <pre> * <foo> * <bar> * <prop>some value</prop> * <prop>other value</prop> * <prop>last value</prop> * </bar> * </foo> * </pre> * * @param name the name of the property. * @param values the values for the property (can be empty but not null). */ public void setProperties(String name, List<String> values) { String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy, // stopping one short. Element element = document.getRootElement(); for (int i = 0; i < propName.length - 1; i++) { // If we don't find this part of the property in the XML heirarchy // we add it as a new node if (element.element(propName[i]) == null) { element.addElement(propName[i]); } element = element.element(propName[i]); } String childName = propName[propName.length - 1]; // We found matching property, clear all children. List<Element> toRemove = new ArrayList<Element>(); Iterator iter = element.elementIterator(childName); while (iter.hasNext()) { toRemove.add((Element) iter.next()); } for (iter = toRemove.iterator(); iter.hasNext();) { element.remove((Element) iter.next()); } // Add the new children. for (String value : values) { Element childElement = element.addElement(childName); if (value.startsWith("<![CDATA[")) { Iterator it = childElement.nodeIterator(); while (it.hasNext()) { Node node = (Node) it.next(); if (node instanceof CDATA) { childElement.remove(node); break; } } childElement.addCDATA(value.substring(9, value.length() - 3)); } else { childElement.setText(StringEscapeUtils.escapeXml(value)); } } saveProperties(); // Generate event. Map<String, Object> params = new HashMap<String, Object>(); params.put("value", values); } /** * Return all children property names of a parent property as a String array, * or an empty array if the if there are no children. For example, given * the properties <tt>X.Y.A</tt>, <tt>X.Y.B</tt>, and <tt>X.Y.C</tt>, then * the child properties of <tt>X.Y</tt> are <tt>A</tt>, <tt>B</tt>, and * <tt>C</tt>. * * @param parent the name of the parent property. * @return all child property values for the given parent. */ public String[] getChildrenProperties(String parent) { String[] propName = parsePropertyName(parent); // Search for this property by traversing down the XML heirarchy. Element element = document.getRootElement(); for (String aPropName : propName) { element = element.element(aPropName); if (element == null) { // This node doesn't match this part of the property name which // indicates this property doesn't exist so return empty array. return new String[] {}; } } // We found matching property, return names of children. List children = element.elements(); int childCount = children.size(); String[] childrenNames = new String[childCount]; for (int i = 0; i < childCount; i++) { childrenNames[i] = ((Element) children.get(i)).getName(); } return childrenNames; } /** * Sets the value of the specified property. If the property doesn't * currently exist, it will be automatically created. * * @param name the name of the property to set. * @param value the new value for the property. */ public synchronized void setProperty(String name, String value) { if (!StringEscapeUtils.escapeXml(name).equals(name)) { throw new IllegalArgumentException("Property name cannot contain XML entities."); } if (name == null) { return; } if (value == null) { value = ""; } // Set cache correctly with prop name and value. propertyCache.put(name, value); String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy. Element element = document.getRootElement(); for (String aPropName : propName) { // If we don't find this part of the property in the XML heirarchy // we add it as a new node if (element.element(aPropName) == null) { element.addElement(aPropName); } element = element.element(aPropName); } // Set the value of the property in this node. if (value.startsWith("<![CDATA[")) { Iterator it = element.nodeIterator(); while (it.hasNext()) { Node node = (Node) it.next(); if (node instanceof CDATA) { element.remove(node); break; } } element.addCDATA(value.substring(9, value.length() - 3)); } else { element.setText(value); } // Write the XML properties to disk saveProperties(); // Generate event. Map<String, Object> params = new HashMap<String, Object>(); params.put("value", value); } /** * Deletes the specified property. * * @param name the property to delete. */ public synchronized void deleteProperty(String name) { // Remove property from cache. propertyCache.remove(name); String[] propName = parsePropertyName(name); // Search for this property by traversing down the XML heirarchy. Element element = document.getRootElement(); for (int i = 0; i < propName.length - 1; i++) { element = element.element(propName[i]); // Can't find the property so return. if (element == null) { return; } } // Found the correct element to remove, so remove it... element.remove(element.element(propName[propName.length - 1])); // .. then write to disk. saveProperties(); // Generate event. Map<String, Object> params = Collections.emptyMap(); } /** * Builds the document XML model up based the given reader of XML data. * @param in the input stream used to build the xml document * @throws java.io.IOException thrown when an error occurs reading the input stream. */ private void buildDoc(Reader in) throws IOException { try { SAXReader xmlReader = new SAXReader(); xmlReader.setEncoding("UTF-8"); document = xmlReader.read(in); } catch (Exception e) { throw new IOException(e.getMessage()); } finally { if (in != null) { in.close(); } } } /** * Saves the properties to disk as an XML document. A temporary file is * used during the writing process for maximum safety. */ private synchronized void saveProperties() { boolean error = false; // Write data out to a temporary file first. File tempFile = null; Writer writer = null; try { tempFile = new File(file.getParentFile(), file.getName() + ".tmp"); writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(tempFile), "UTF-8")); OutputFormat prettyPrinter = OutputFormat.createPrettyPrint(); XMLWriter xmlWriter = new XMLWriter(writer, prettyPrinter); xmlWriter.write(document); } catch (Exception e) { // There were errors so abort replacing the old property file. error = true; } finally { if (writer != null) { try { writer.close(); } catch (IOException e1) { error = true; } } } // No errors occured, so delete the main file. if (!error) { // Delete the old file so we can replace it. if (!file.delete()) { return; } // Copy new contents to the file. try { copy(tempFile, file); } catch (Exception e) { // There were errors so abort replacing the old property file. error = true; } // If no errors, delete the temp file. if (!error) { tempFile.delete(); } } } /** * Returns an array representation of the given Jive property. Jive * properties are always in the format "prop.name.is.this" which would be * represented as an array of four Strings. * * @param name the name of the Jive property. * @return an array representation of the given Jive property. */ private String[] parsePropertyName(String name) { List<String> propName = new ArrayList<String>(5); // Use a StringTokenizer to tokenize the property name. StringTokenizer tokenizer = new StringTokenizer(name, "."); while (tokenizer.hasMoreTokens()) { propName.add(tokenizer.nextToken()); } return propName.toArray(new String[propName.size()]); } public void setProperties(Map<String, String> propertyMap) { for (String propertyName : propertyMap.keySet()) { String propertyValue = propertyMap.get(propertyName); setProperty(propertyName, propertyValue); } } /** * Copies the inFile to the outFile. * * @param inFile The file to copy from * @param outFile The file to copy to * @throws IOException If there was a problem making the copy */ private static void copy(File inFile, File outFile) throws IOException { FileInputStream fin = null; FileOutputStream fout = null; try { fin = new FileInputStream(inFile); fout = new FileOutputStream(outFile); copy(fin, fout); } finally { try { if (fin != null) fin.close(); } catch (IOException e) { // do nothing } try { if (fout != null) fout.close(); } catch (IOException e) { // do nothing } } } /** * Copies data from an input stream to an output stream * * @param in the stream to copy data from. * @param out the stream to copy data to. * @throws IOException if there's trouble during the copy. */ private static void copy(InputStream in, OutputStream out) throws IOException { // Do not allow other threads to intrude on streams during copy. synchronized (in) { synchronized (out) { byte[] buffer = new byte[256]; while (true) { int bytesRead = in.read(buffer); if (bytesRead == -1) break; out.write(buffer, 0, bytesRead); } } } } }