Java tutorial
/* * Copyright 2002-2010 the original author or authors. * * 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.springframework.integration.expression; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Locale; import java.util.Map; import java.util.Properties; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.context.ResourceLoaderAware; import org.springframework.core.io.DefaultResourceLoader; import org.springframework.core.io.Resource; import org.springframework.core.io.ResourceLoader; import org.springframework.expression.Expression; import org.springframework.expression.ExpressionParser; import org.springframework.expression.spel.SpelParserConfiguration; import org.springframework.expression.spel.standard.SpelExpressionParser; import org.springframework.util.Assert; import org.springframework.util.DefaultPropertiesPersister; import org.springframework.util.PropertiesPersister; import org.springframework.util.StringUtils; /** * {@link ExpressionSource} implementation that accesses resource bundles using specified basenames. * This class uses {@link java.util.Properties} instances as its custom data structure for expressions, * loading them via a {@link org.springframework.util.PropertiesPersister} strategy: The default * strategy is capable of loading properties files with a specific character encoding, if desired. * * @author Juergen Hoeller * @author Mark Fisher * @since 2.0 * @see #setCacheSeconds * @see #setBasenames * @see #setDefaultEncoding * @see #setFileEncodings * @see #setPropertiesPersister * @see #setResourceLoader * @see org.springframework.util.DefaultPropertiesPersister * @see org.springframework.core.io.DefaultResourceLoader * @see java.util.ResourceBundle */ public class ReloadableResourceBundleExpressionSource implements ExpressionSource, ResourceLoaderAware { private static final String PROPERTIES_SUFFIX = ".properties"; private static final String XML_SUFFIX = ".xml"; private static final Log logger = LogFactory.getLog(ReloadableResourceBundleExpressionSource.class); private volatile String[] basenames = new String[0]; private volatile String defaultEncoding; private volatile Properties fileEncodings; private volatile boolean fallbackToSystemLocale = true; private volatile long cacheMillis = -1; private volatile PropertiesPersister propertiesPersister = new DefaultPropertiesPersister(); private volatile ResourceLoader resourceLoader = new DefaultResourceLoader(); /** Cache to hold filename lists per Locale */ private final Map<String, Map<Locale, List<String>>> cachedFilenames = new HashMap<String, Map<Locale, List<String>>>(); /** Cache to hold already loaded properties per filename */ private final Map<String, PropertiesHolder> cachedProperties = new HashMap<String, PropertiesHolder>(); /** Cache to hold merged loaded properties per locale */ private final Map<Locale, PropertiesHolder> cachedMergedProperties = new HashMap<Locale, PropertiesHolder>(); private final ExpressionParser parser = new SpelExpressionParser(new SpelParserConfiguration(true, true)); /** * Set a single basename, following the basic ResourceBundle convention of * not specifying file extension or language codes, but referring to a Spring * resource location: e.g. "META-INF/expressions" for "META-INF/expressions.properties", * "META-INF/expressions_en.properties", etc. * <p>XML properties files are also supported: .g. "META-INF/expressions" will find * and load "META-INF/expressions.xml", "META-INF/expressions_en.xml", etc as well. * @param basename the single basename * @see #setBasenames * @see org.springframework.core.io.ResourceEditor * @see java.util.ResourceBundle */ public void setBasename(String basename) { setBasenames(new String[] { basename }); } /** * Set an array of basenames, each following the basic ResourceBundle convention * of not specifying file extension or language codes, but referring to a Spring * resource location: e.g. "META-INF/expressions" for "META-INF/expressions.properties", * "META-INF/expressions_en.properties", etc. * <p>XML properties files are also supported: .g. "META-INF/expressions" will find * and load "META-INF/expressions.xml", "META-INF/expressions_en.xml", etc as well. * <p>The associated resource bundles will be checked sequentially when resolving * an expression key. Note that expression definitions in a <i>previous</i> resource * bundle will override ones in a later bundle, due to the sequential lookup. * @param basenames an array of basenames * @see #setBasename * @see java.util.ResourceBundle */ public void setBasenames(String[] basenames) { if (basenames != null) { this.basenames = new String[basenames.length]; for (int i = 0; i < basenames.length; i++) { String basename = basenames[i]; Assert.hasText(basename, "Basename must not be empty"); this.basenames[i] = basename.trim(); } } else { this.basenames = new String[0]; } } /** * Set the default charset to use for parsing properties files. * Used if no file-specific charset is specified for a file. * <p>Default is none, using the <code>java.util.Properties</code> * default encoding. * <p>Only applies to classic properties files, not to XML files. * @param defaultEncoding the default charset * @see #setFileEncodings * @see org.springframework.util.PropertiesPersister#load */ public void setDefaultEncoding(String defaultEncoding) { this.defaultEncoding = defaultEncoding; } /** * Set per-file charsets to use for parsing properties files. * <p>Only applies to classic properties files, not to XML files. * @param fileEncodings Properties with filenames as keys and charset * names as values. Filenames have to match the basename syntax, * with optional locale-specific appendices: e.g. "META-INF/expressions" * or "META-INF/expressions_en". * @see #setBasenames * @see org.springframework.util.PropertiesPersister#load */ public void setFileEncodings(Properties fileEncodings) { this.fileEncodings = fileEncodings; } /** * Set whether to fall back to the system Locale if no files for a specific * Locale have been found. Default is "true"; if this is turned off, the only * fallback will be the default file (e.g. "expressions.properties" for * basename "expressions"). * <p>Falling back to the system Locale is the default behavior of * <code>java.util.ResourceBundle</code>. However, this is often not * desirable in an application server environment, where the system Locale * is not relevant to the application at all: Set this flag to "false" * in such a scenario. */ public void setFallbackToSystemLocale(boolean fallbackToSystemLocale) { this.fallbackToSystemLocale = fallbackToSystemLocale; } /** * Set the number of seconds to cache loaded properties files. * <ul> * <li>Default is "-1", indicating to cache forever (just like * <code>java.util.ResourceBundle</code>). * <li>A positive number will cache loaded properties files for the given * number of seconds. This is essentially the interval between refresh checks. * Note that a refresh attempt will first check the last-modified timestamp * of the file before actually reloading it; so if files don't change, this * interval can be set rather low, as refresh attempts will not actually reload. * <li>A value of "0" will check the last-modified timestamp of the file on * every expression access. <b>Do not use this in a production environment!</b> * </ul> */ public void setCacheSeconds(int cacheSeconds) { this.cacheMillis = (cacheSeconds * 1000); } /** * Set the PropertiesPersister to use for parsing properties files. * <p>The default is a DefaultPropertiesPersister. * @see org.springframework.util.DefaultPropertiesPersister */ public void setPropertiesPersister(PropertiesPersister propertiesPersister) { this.propertiesPersister = (propertiesPersister != null ? propertiesPersister : new DefaultPropertiesPersister()); } /** * Set the ResourceLoader to use for loading bundle properties files. * <p>The default is a DefaultResourceLoader. Will get overridden by the * ApplicationContext if running in a context, as it implements the * ResourceLoaderAware interface. Can be manually overridden when * running outside of an ApplicationContext. * @see org.springframework.core.io.DefaultResourceLoader * @see org.springframework.context.ResourceLoaderAware */ public void setResourceLoader(ResourceLoader resourceLoader) { this.resourceLoader = (resourceLoader != null ? resourceLoader : new DefaultResourceLoader()); } /** * Resolves the given key in the retrieved bundle files to an Expression. */ public Expression getExpression(String key, Locale locale) { String expressionString = this.getExpressionString(key, locale); if (expressionString != null) { return this.parser.parseExpression(expressionString); } return null; } private String getExpressionString(String key, Locale locale) { if (this.cacheMillis < 0) { PropertiesHolder propHolder = getMergedProperties(locale); String result = propHolder.getProperty(key); if (result != null) { return result; } } else { for (String basename : this.basenames) { List<String> filenames = calculateAllFilenames(basename, locale); for (String filename : filenames) { PropertiesHolder propHolder = getProperties(filename); String result = propHolder.getProperty(key); if (result != null) { return result; } } } } return null; } /** * Get a PropertiesHolder that contains the actually visible properties * for a Locale, after merging all specified resource bundles. * Either fetches the holder from the cache or freshly loads it. * <p>Only used when caching resource bundle contents forever, i.e. * with cacheSeconds < 0. Therefore, merged properties are always * cached forever. */ private PropertiesHolder getMergedProperties(Locale locale) { synchronized (this.cachedMergedProperties) { PropertiesHolder mergedHolder = this.cachedMergedProperties.get(locale); if (mergedHolder != null) { return mergedHolder; } Properties mergedProps = new Properties(); mergedHolder = new PropertiesHolder(mergedProps, -1); for (int i = this.basenames.length - 1; i >= 0; i--) { List<String> filenames = calculateAllFilenames(this.basenames[i], locale); for (int j = filenames.size() - 1; j >= 0; j--) { String filename = filenames.get(j); PropertiesHolder propHolder = getProperties(filename); if (propHolder.getProperties() != null) { mergedProps.putAll(propHolder.getProperties()); } } } this.cachedMergedProperties.put(locale, mergedHolder); return mergedHolder; } } /** * Calculate all filenames for the given bundle basename and Locale. * Will calculate filenames for the given Locale, the system Locale * (if applicable), and the default file. * @param basename the basename of the bundle * @param locale the locale * @return the List of filenames to check * @see #setFallbackToSystemLocale * @see #calculateFilenamesForLocale */ private List<String> calculateAllFilenames(String basename, Locale locale) { synchronized (this.cachedFilenames) { Map<Locale, List<String>> localeMap = this.cachedFilenames.get(basename); if (localeMap != null) { List<String> filenames = localeMap.get(locale); if (filenames != null) { return filenames; } } List<String> filenames = new ArrayList<String>(7); filenames.addAll(calculateFilenamesForLocale(basename, locale)); if (this.fallbackToSystemLocale && !locale.equals(Locale.getDefault())) { List<String> fallbackFilenames = calculateFilenamesForLocale(basename, Locale.getDefault()); for (String fallbackFilename : fallbackFilenames) { if (!filenames.contains(fallbackFilename)) { // Entry for fallback locale that isn't already in filenames list. filenames.add(fallbackFilename); } } } filenames.add(basename); if (localeMap != null) { localeMap.put(locale, filenames); } else { localeMap = new HashMap<Locale, List<String>>(); localeMap.put(locale, filenames); this.cachedFilenames.put(basename, localeMap); } return filenames; } } /** * Calculate the filenames for the given bundle basename and Locale, * appending language code, country code, and variant code. * E.g.: basename "expressions", Locale "de_AT_oo" -> "expressions_de_AT_OO", * "expressions_de_AT", "expressions_de". * <p>Follows the rules defined by {@link java.util.Locale#toString()}. * @param basename the basename of the bundle * @param locale the locale * @return the List of filenames to check */ private List<String> calculateFilenamesForLocale(String basename, Locale locale) { List<String> result = new ArrayList<String>(3); String language = locale.getLanguage(); String country = locale.getCountry(); String variant = locale.getVariant(); StringBuilder temp = new StringBuilder(basename); temp.append('_'); if (language.length() > 0) { temp.append(language); result.add(0, temp.toString()); } temp.append('_'); if (country.length() > 0) { temp.append(country); result.add(0, temp.toString()); } if (variant.length() > 0 && (language.length() > 0 || country.length() > 0)) { temp.append('_').append(variant); result.add(0, temp.toString()); } return result; } /** * Get a PropertiesHolder for the given filename, either from the * cache or freshly loaded. * @param filename the bundle filename (basename + Locale) * @return the current PropertiesHolder for the bundle */ private PropertiesHolder getProperties(String filename) { synchronized (this.cachedProperties) { PropertiesHolder propHolder = this.cachedProperties.get(filename); if (propHolder != null && (propHolder.getRefreshTimestamp() < 0 || propHolder.getRefreshTimestamp() > System.currentTimeMillis() - this.cacheMillis)) { return propHolder; } return refreshProperties(filename, propHolder); } } /** * Refresh the PropertiesHolder for the given bundle filename. * The holder can be <code>null</code> if not cached before, or a timed-out cache entry * (potentially getting re-validated against the current last-modified timestamp). * @param filename the bundle filename (basename + Locale) * @param propHolder the current PropertiesHolder for the bundle */ private PropertiesHolder refreshProperties(String filename, PropertiesHolder propHolder) { long refreshTimestamp = (this.cacheMillis < 0) ? -1 : System.currentTimeMillis(); Resource resource = this.resourceLoader.getResource(filename + PROPERTIES_SUFFIX); if (!resource.exists()) { resource = this.resourceLoader.getResource(filename + XML_SUFFIX); } if (resource.exists()) { long fileTimestamp = -1; if (this.cacheMillis >= 0) { // Last-modified timestamp of file will just be read if caching with timeout. try { fileTimestamp = resource.lastModified(); if (propHolder != null && propHolder.getFileTimestamp() == fileTimestamp) { if (logger.isDebugEnabled()) { logger.debug("Re-caching properties for filename [" + filename + "] - file hasn't been modified"); } propHolder.setRefreshTimestamp(refreshTimestamp); return propHolder; } } catch (IOException ex) { // Probably a class path resource: cache it forever. if (logger.isDebugEnabled()) { logger.debug(resource + " could not be resolved in the file system - assuming that is hasn't changed", ex); } fileTimestamp = -1; } } try { Properties props = loadProperties(resource, filename); propHolder = new PropertiesHolder(props, fileTimestamp); } catch (IOException ex) { if (logger.isWarnEnabled()) { logger.warn("Could not parse properties file [" + resource.getFilename() + "]", ex); } // Empty holder representing "not valid". propHolder = new PropertiesHolder(); } } else { // Resource does not exist. if (logger.isDebugEnabled()) { logger.debug("No properties file found for [" + filename + "] - neither plain properties nor XML"); } // Empty holder representing "not found". propHolder = new PropertiesHolder(); } propHolder.setRefreshTimestamp(refreshTimestamp); this.cachedProperties.put(filename, propHolder); return propHolder; } /** * Load the properties from the given resource. * @param resource the resource to load from * @param filename the original bundle filename (basename + Locale) * @return the populated Properties instance * @throws IOException if properties loading failed */ private Properties loadProperties(Resource resource, String filename) throws IOException { InputStream is = resource.getInputStream(); Properties props = new Properties(); try { if (resource.getFilename().endsWith(XML_SUFFIX)) { if (logger.isDebugEnabled()) { logger.debug("Loading properties [" + resource.getFilename() + "]"); } this.propertiesPersister.loadFromXml(props, is); } else { String encoding = null; if (this.fileEncodings != null) { encoding = this.fileEncodings.getProperty(filename); } if (encoding == null) { encoding = this.defaultEncoding; } if (encoding != null) { if (logger.isDebugEnabled()) { logger.debug("Loading properties [" + resource.getFilename() + "] with encoding '" + encoding + "'"); } this.propertiesPersister.load(props, new InputStreamReader(is, encoding)); } else { if (logger.isDebugEnabled()) { logger.debug("Loading properties [" + resource.getFilename() + "]"); } this.propertiesPersister.load(props, is); } } return props; } finally { is.close(); } } /** * Clear the resource bundle cache. * Subsequent resolve calls will lead to reloading of the properties files. */ public void clearCache() { logger.debug("Clearing entire resource bundle cache"); synchronized (this.cachedProperties) { this.cachedProperties.clear(); } synchronized (this.cachedMergedProperties) { this.cachedMergedProperties.clear(); } } @Override public String toString() { return getClass().getName() + ": basenames=[" + StringUtils.arrayToCommaDelimitedString(this.basenames) + "]"; } /** * PropertiesHolder for caching. * Stores the last-modified timestamp of the source file for efficient * change detection, and the timestamp of the last refresh attempt * (updated every time the cache entry gets re-validated). */ private class PropertiesHolder { private Properties properties; private long fileTimestamp = -1; private long refreshTimestamp = -1; public PropertiesHolder(Properties properties, long fileTimestamp) { this.properties = properties; this.fileTimestamp = fileTimestamp; } public PropertiesHolder() { } public Properties getProperties() { return properties; } public long getFileTimestamp() { return fileTimestamp; } public void setRefreshTimestamp(long refreshTimestamp) { this.refreshTimestamp = refreshTimestamp; } public long getRefreshTimestamp() { return refreshTimestamp; } public String getProperty(String code) { if (this.properties == null) { return null; } return this.properties.getProperty(code); } } }