Java tutorial
/* * Copyright 2004-2005 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.util; import java.io.IOException; import java.io.InputStream; import java.util.HashMap; import java.util.Iterator; import java.util.Locale; import java.util.Properties; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * Concrete subclass of <code>MessageResources</code> that reads message keys * and corresponding strings from named property resources in the same manner * that <code>java.util.PropertyResourceBundle</code> does. The * <code>base</code> property defines the base property resource name, and * must be specified. * <p> * <strong>IMPLEMENTATION NOTE</strong> - This class trades memory for * speed by caching all messages located via generalizing the Locale under * the original locale as well. * This results in specific messages being stored in the message cache * more than once, but improves response time on subsequent requests for * the same locale + key combination. * * @author Craig R. McClanahan * @author David Graham * @version $Revision: 1.8 $ $Date: 2003/04/19 19:06:02 $ */ public class PropertyMessageResources extends MessageResources { // ----------------------------------------------------------- Constructors /** * Construct a new PropertyMessageResources according to the * specified parameters. * * @param factory The MessageResourcesFactory that created us * @param config The configuration parameter for this MessageResources */ public PropertyMessageResources(MessageResourcesFactory factory, String config) { super(factory, config); log.info("Initializing, config='" + config + "'"); } /** * Construct a new PropertyMessageResources according to the * specified parameters. * * @param factory The MessageResourcesFactory that created us * @param config The configuration parameter for this MessageResources * @param returnNull The returnNull property we should initialize with */ public PropertyMessageResources(MessageResourcesFactory factory, String config, boolean returnNull) { super(factory, config, returnNull); log.info("Initializing, config='" + config + "', returnNull=" + returnNull); } // ------------------------------------------------------------- Properties /** * The set of locale keys for which we have already loaded messages, keyed * by the value calculated in <code>localeKey()</code>. */ protected HashMap locales = new HashMap(); /** * The <code>Log</code> instance for this class. */ protected static final Log log = LogFactory.getLog(PropertyMessageResources.class); /** * The cache of messages we have accumulated over time, keyed by the * value calculated in <code>messageKey()</code>. */ protected HashMap messages = new HashMap(); // --------------------------------------------------------- Public Methods /** * Returns a text message for the specified key, for the default Locale. * A null string result will be returned by this method if no relevant * message resource is found for this key or Locale, if the * <code>returnNull</code> property is set. Otherwise, an appropriate * error message will be returned. * <p> * This method must be implemented by a concrete subclass. * * @param locale The requested message Locale, or <code>null</code> * for the system default Locale * @param key The message key to look up * @return text message for the specified key and locale */ public String getMessage(Locale locale, String key) { if (log.isDebugEnabled()) { log.debug("getMessage(" + locale + "," + key + ")"); } // Initialize variables we will require String localeKey = localeKey(locale); String originalKey = messageKey(localeKey, key); String messageKey = null; String message = null; int underscore = 0; boolean addIt = false; // Add if not found under the original key // Loop from specific to general Locales looking for this message while (true) { // Load this Locale's messages if we have not done so yet loadLocale(localeKey); // Check if we have this key for the current locale key messageKey = messageKey(localeKey, key); synchronized (messages) { message = (String) messages.get(messageKey); if (message != null) { if (addIt) { messages.put(originalKey, message); } return (message); } } // Strip trailing modifiers to try a more general locale key addIt = true; underscore = localeKey.lastIndexOf("_"); if (underscore < 0) { break; } localeKey = localeKey.substring(0, underscore); } // Try the default locale if the current locale is different if (!defaultLocale.equals(locale)) { localeKey = localeKey(defaultLocale); messageKey = messageKey(localeKey, key); loadLocale(localeKey); synchronized (messages) { message = (String) messages.get(messageKey); if (message != null) { messages.put(originalKey, message); return (message); } } } // As a last resort, try the default Locale localeKey = ""; messageKey = messageKey(localeKey, key); loadLocale(localeKey); synchronized (messages) { message = (String) messages.get(messageKey); if (message != null) { messages.put(originalKey, message); return (message); } } // Return an appropriate error indication if (returnNull) { return (null); } else { return ("???" + messageKey(locale, key) + "???"); } } // ------------------------------------------------------ Protected Methods /** * Load the messages associated with the specified Locale key. For this * implementation, the <code>config</code> property should contain a fully * qualified package and resource name, separated by periods, of a series * of property resources to be loaded from the class loader that created * this PropertyMessageResources instance. This is exactly the same name * format you would use when utilizing the * <code>java.util.PropertyResourceBundle</code> class. * * @param localeKey Locale key for the messages to be retrieved */ protected synchronized void loadLocale(String localeKey) { if (log.isTraceEnabled()) { log.trace("loadLocale(" + localeKey + ")"); } // Have we already attempted to load messages for this locale? if (locales.get(localeKey) != null) { return; } locales.put(localeKey, localeKey); // Set up to load the property resource for this locale key, if we can String name = config.replace('.', '/'); if (localeKey.length() > 0) { name += "_" + localeKey; } name += ".properties"; InputStream is = null; Properties props = new Properties(); // Load the specified property resource if (log.isTraceEnabled()) { log.trace(" Loading resource '" + name + "'"); } ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); if (classLoader == null) { classLoader = this.getClass().getClassLoader(); } is = classLoader.getResourceAsStream(name); if (is != null) { try { props.load(is); } catch (IOException e) { log.error("loadLocale()", e); } finally { try { is.close(); } catch (IOException e) { log.error("loadLocale()", e); } } } if (log.isTraceEnabled()) { log.trace(" Loading resource completed"); } // Copy the corresponding values into our cache if (props.size() < 1) { return; } synchronized (messages) { Iterator names = props.keySet().iterator(); while (names.hasNext()) { String key = (String) names.next(); if (log.isTraceEnabled()) { log.trace(" Saving message key '" + messageKey(localeKey, key)); } messages.put(messageKey(localeKey, key), props.getProperty(key)); } } } }